Chemistry Markscheme (All in One)

June 2003

INTERNATIONAL GCSE

MARKING SCHEME

MAXIMUM MARK: 40

SYLLABUS/COMPONENT: 0620/01

CHEMISTRY

(Multiple Choice)

www.XtremePapers.com

Mark Scheme Syllabus Paper

IGCSE EXAMINATIONS – June 2003 0620 1

© University of Cambridge Local Examinations Syndicate 2003

QuestionNumber

KeyQuestionNumber

Key

1 C 21 B

2 B 22 D

3 A 23 A

4 D 24 B

5 A 25 D

6 C 26 B

7 A 27 D

8 A 28 D

9 B 29 D

10 C 30 B

11 B 31 D

12 D 32 D

13 C 33 A

14 D 34 A

15 B 35 B

16 C 36 A

17 A 37 A

18 C 38 B

19 A 39 C

20 C 40 C

TOTAL 40

June 2003

INTERNATIONAL GCSE

MARKING SCHEME

MAXIMUM MARK: 80


CHEMISTRY

(Core Paper 2)




1 (a) (i) Fe/Cu ALLOW Zn [1](ii) C/N/S/F/Cl/Br [1](iii) O/S [1](iv) C [1](v) Li/Na/K ALLOW F [1](vi) CU/Zn/Br/Kr [1]

(b) argon - light bulbs;chlorine - kills bacteria;carbon - as lubricant;helium - in balloons [4]

(c) (i) covalent [1](ii) BrF5 ALLOW F5Br [1](iii) ions/charged particles;

NOT: particlesnot free to move in solid/free to move in molten/liquid state [2]

2 (a) drop small tube in acid/loosen string/idea of mixing zinc and acid/let go ofcottonALLOW: cut the string [1]NOT: heat (the acid)NOT: pull the string

(b) (i) correct plotting including 0-0 point ( �1 per omission or error) [2](ii) best curve drawn and to go through origin [1](iii) no more gas produced/reaction finished;

all zinc reacted/used up [2]

(c) graph drawn with faster initial rate and starting at 0-0;ALLOW: straight line as initial rateends up at 55 cm3 [2]

(d) (i) 2 (HCl) [1](ii) zinc chloride [1](iii) 136 [1]

IGNORE units

(e) substance containing only one type of atom/substance which cannot be brokendown to any other substance by chemical means [1]NOT ‘can’t be split’ aloneNOT is a pure substance

3 (a) (i) evaporation/vaporisation/boiling [1](ii) freezing/solidification [1]

NOT: fusion(iii) condensing/condensation/liquefaction [1]

(b) 2nd box ticked [1]

(c) A;energy needed to overcome forces between molecules/idea of energy input/taking in heat [2]

(d) (i) chlorine [1](ii) bromine [1](iii) sodium chloride [1]




(e) (i) diffusion [1]NOT: Brownian motion

(ii) ammonium chloride [1]NOT: ammonia chloride

(iii) ammonia diffuses or moves faster/HCl diffuses or moves slower/ammonia haslower mass/HCl higher mass/molecules of HCl and ammonia move at differentspeeds [1]NOT: ammonia evaporates faster/HCl evaporates more slowly

(f) neutralisation/acid base [1]NOT: exothermicNOT: addition

(g) (i) thermometer [1](ii) reference to the solid or melting point of the solid is needed for the mark.

boiling point of water too low to get solid to melt/boiling water cannot get to155°C [1]NOT: boiling point of water is only 100°C/boiling point of water too low.NOT: water boils off first

(iii) so that the liquid is the same temperature throughout/no hot or cold spots/sothe tube is the same temperature as the thermometer/so heat can circulate inall places [1]ALLOW: so that temperature of liquid is balancedNOT: to keep temperature constant

4 (a) (i) breaking down of molecules substances using heat [1](ii) substance which speeds up a reaction [1]

NOT: alters/changes rate of reactionNOT: speeds up and slows down rate

(b) ethene/ethylene [1]NOT: formula

(c) (i) paraffin [1](ii) 4000g/4kg [1]

(correct unit needed)(iii) C2H4; H2 [2]

(d) (i) two units polymerised with continuation bonds at either end and hydrogenatoms drawn [1]ALLOW: �CH2CH2CH2CH2 �

ALLOW: � [ �CH2CH2 � ] � n

ALLOW: � [ �CH2 � ] � n

(ii) addition (polymerisation) [1]

5 (a) (sodium) hydroxide/ammonia; → green/grey green; [2]silver nitrate; → yellow; [2]ALLOW: lead nitrate NOT: creamALLOW: bubble chlorine → grey/black (precipitate)silver nitrate; → white: [2]barium chloride/nitrate; → white; [2]ALLOW: lead acetate




(b) filtration/filtering or diagram of correct apparatus for filtration (filter paper mustbe present on diagram)NOT: decantingsodium chloride through filter paper/shown on diagram;NOT: filtrate through filter paperevaporate off water from sodium chloride/suitable diagram [3]ALLOW: distilling off water

(c) different atoms/elements(chemically) joined/bonded/combined (both points needed)(reference to mixtures = 0 unless qualified enough in time frame e.g. a mixtureof elements which are then chemically combined) [1]

(d) (i) chlorine/Cl2 [1](ii) sodium/Na [1]

6 (a) potassium/magnesium/aluminium [1]

(b) they did not have electricity/did not know about electrolysis/did not know themetal existed [1]NOT: did not have the right technology

(c) (i) indication that bubbles produced rapidly or quickly/slower than magnesium butfaster than zincOR number of bubbles produced intermediate between magnesium and zinc; [1]uranium dissolved slower than magnesium but faster than zinc/dissolves atmedium rate etc. [1]

(ii) atoms of same element with different mass number/different number ofneutrons/different nucleon number [1]NOT: compounds/molecules with different mass number

(iii) indication of use for energy – nuclear power stations/nuclear energy [1]ALLOW: atomic/nuclear bombsNOT: curing cancer/medical usesNOT: ‘for fuel’

(d) magnesium oxideALLOW: MgO [1]

(e) (i) idea of mixture of (different) metals [1](ii) alloys harder/stronger/decreased malleability/increased toughness/increased

corrosion resistance/heat or electrical resistance increased [1]NOT: increase in melting pointNOT: cheaperNOT: improving properties

(f) removes oxygen from zinc oxide [1]ALLOW: definition of reduction involving oxidation numbers/electron transfer

(g) (i) reversible reaction [1]ALLOW: equilibrium

(ii) 76-80% [1]

(h) (i) correct electronic structure of Mg (2.8.2) on diagram [1](ii) loses two electrons/loses its valence electrons = 2

forms Mg2+ ion = 1loses electron(s) = 1 [2]forms Mg2+ ion by losing electrons = 2

June 2003

INTERNATIONAL GCSE

MARKING SCHEME

MAXIMUM MARK: 80


CHEMISTRY

(Extended Paper 3)




In the mark scheme if a word or phrase is underlined it (or an equivalent) is required for the awardof the mark.

(......) is used to denote material that is not specifically required.

OR designates alternative and independent ways of gaining the marks for the question.

or indicates different ways of gaining the same mark.

COND indicates that the award of this mark is conditional upon a previous mark being gained.

� Unusual responses which include correct Chemistry that answers the question shouldalways be rewarded-even if they are not mentioned in the marking scheme.

� All the candidate's work must show evidence of being marked by the examiner.

1 (a) A correct equation either CO or CO2 as productIf not balanced but otherwise correct [1] ONLY [2]

(b) (i) C + O2 � CO2 NOT word equation [1](ii) (higher in furnace) no oxygen left

carbon dioxide reacts with carbon (to give carbon monoxide)

OR incomplete combustion of carbon

OR either equation gains both marksCO2 + C = 2CO or 2C + O2 = 2CO

OR carbon dioxide reactswith carbon

[1][1]

[2]

[1][1]

(c) limestone + sand � slag

OR calcium carbonate + silicon (IV) oxide � calcium silicate (+ carbon dioxide)

For knowing that impurity is sand [1] ONLY

Accept calcium oxide and silicon oxideAccept lime

[2]

(d) (i) Cutlery or chemical plant or watches or utensils or surgical instruments orcars or sinks or aircraft or garden tools [1]

(ii) nickel or chromium or molybdenum or niobium or titanium [1](iii) blow air/oxygen through

carbon becomes carbon dioxidecarbon dioxide escapes as gassilicon and phosphorus become oxidescalcium oxide or calcium carbonateforms slagAny FOUR NOT blast furnace [4]

(e) anode tin NOT impure timecathode iron or steeltin salt or tin ions as electrolyteNOT oxide or hydroxide or carbonate

[1][1][1]

TOTAL = 16




2 (a) (i) 3 ignore any charges [1](ii) high melting or boiling point

hardpoor conductor of electricity or heatbrittleAny TWONOT insoluble, dull, or malleable

[2]

(iii) carbon, graphite diamond silicon, germaniumsilicon (IV) oxide or silica or silicon dioxide or silicon oxideor sand or silicon carbide or named polymer

[1]

[1](iv) four around one

cond looks tetrahedral or shows continuationFor graphite layers [1] weak bonds between layers [1]Accept any macromolecule, no link with (iii)For polymer repeat unit [1] continuation [1]

[1][1]

(b) (i) white precipitateCOND upon a precipitatedissolves in excess or forms solution

[1]

[1](ii) blue precipitate

COND upon a precipitatedoes not dissolve in excess

[1]

[1]

(c) (i) number of moles CO2 = 0.24/24 = 0.01conseq number of moles of CaCO3 and MgCO3 = 0.01conseq number of moles of CaCO3 = 0.005 [3]

(ii) Calculate the volume of hydrochloric acid, 1.0 mole/dm3, needed to react withone tablet.number of moles of CaCO3 and MgCO3 in one tablet = 0.01Expect same as answer to (c)(i). NO marks to be awarded. Just markconsequentially to this responseconseq number of moles of HCl neededto react with one tablet = 0.02

conseq volume of hydrochloric acid, 1.0 mole/dm3, needed to react with onetablet = 0.02 dm3 or 20 cm3

[1]

[1]

TOTAL = 16

3 (a) (i) Correct equationFor giving correct formula of alkane and alkene [1] onlyAccept alkene and hydrogen

[2]

(ii) chlorineCOND light or 200°C or heat or lead tetraethylor high temperature MAX 1000°Cignore comment ‘catalyst’

[1]

[1]

(b) (i) same molecular formuladifferent structures or structural formulae

[1][1]

(ii) but-2-ene or cyclobutanecorresponding structural formulaNOT 2-butene

[1][1]

(c) butanol ignore numbersbutane ignore numbersdibromobutane ignore numbers

[1][1][1]




(d) (i) propene

CH3—CH==CH2

[1]

[1]

(ii) Correct structure of repeat unitignore point of attachment of ester groupCOND upon repeat unitshows continuationIf chain through ester group [0] out of [2]

[1]

[1]

(iii) do not decay or non-biodegradableshortage of sites or amount of waste per yearvisual pollutionforms methaneAny TWO [2]

(iv) form poisonous or toxic gases or named gas CO, HCl HCNNOT carbon dioxide, harmful, sulphur dioxide

[1]

TOTAL = 18

4 (a) (i) Correct equationnot balanced [1] ONLY2Pb(NO3)2 = 2PbO + 4NO2 + O2

Pb(NO3)2 = PO + 2 NO2 + 2

1 O2

[2]

(ii) potassium nitrate � potassium nitrite + oxygen [1]

(b) (i) close or tightly packedordered or latticevibrationalNOT forces

[1][1][1]

(ii) melting or freezing or fusion or solidification [1]

(c) (i) oxygen and nitrogen (in air)react at high temperatures (and high pressure)If nitrogen in fuel [0] out of [2]

[1][1]

(ii) catalytic converterreact with carbon monoxide or hydrocarbonsform nitrogenANY TWO [2]

(d) Add excess lead oxide to nitric acidcan imply excessfilter NOT if residue is lead nitrateevaporate or heat solution

[1]

[1][1]

TOTAL = 14

5 (a) protons 2electrons 2neutrons 4 [3]

(b) (i) La3+ + 3e- = La [1](ii) hydrogen

bromine NOT Bromidecaesium hydroxideignore any comments about electrodes

[1][1][1]




(c) metal hydroxide or hydroxide ionshydrogen

[1][1]

(d) correct formula 1Ba to 2Cl

charges correct8e around the anionAll three pointsTwo points ONLY [1]If covalent [0] out [2]

[2]

(e) alternating (positive and negative)pattern

[1][1]

(f) (i) barium - oxygen or ionic [1](ii) bond forming energy released/exothermic

bond breaking energy taken in/endothermicmore energy released

[1][1][1]

TOTAL = 17

Total for Paper: 80

June 2003

INTERNATIONAL GCSE

MARKING SCHEME

MAXIMUM MARK: 40


CHEMISTRY

(Practical)




1 Table of resultsExperiment 1 Initial and final readings recorded

to 1 decimal place[1][1]

Experiment 2 Initial and final readings recordedto 1 decimal place

[1][1]

Results comparable to Supervisor’s results � 1cm3 [2]

(a) red/burgundy/brown [1]

(b) yellow (1) to blue/black (1) see Supervisor [2]IGNORE green

(c) (i) Experiment 1 [1](ii) � 2 x, double volume (1) in Experiment 1 (1) not just more [2](iii) potassium iodate less concentrated solution C than B or vice versa [1]

not different concentrations(iv) 2 x volume from table for Experiment 1 (1) unit (1) [2]

2 x iodine formed [1]

(d) Indicator (1) reference to accuracy (1)/end-point/see more clearly [2]not test for I2/I

�

[Question total: 18]

2 (a) bubbles/condensation/goes black max 2 [2]

(b) filtrate - colourless not clearresidue - green

[1][1]

(c) (i) effervescence/fizz/bubbleslimewater → milkysolution is blue

[1][1][1]

(ii) blue (1) precipitate (1)royal/deep blue (1) solution (1)

[2][2]

(d) (i) white (1) precipitate (1) dissolves in excess (1) [3](ii) white (1) precipitate (1) dissolves (1) [3](iii) white precipitate (1) [1]

(e) zinc (1) sulphate (1) reversed = 0 [2]

(f) copper (1) carbonate (1) reversed = 0 [2]hydrated (1) max 2

[Question total: 22]

[Total for paper: 40]

Results obtained for Question 1/cm3

1st 2nd

Experiment 1 16.5 16.3Experiment 2 8.3 8.2

June 2003

INTERNATIONAL GCSE

MARKING SCHEME

MAXIMUM MARK: 60


CHEMISTRY

(Alternative to Practical)




1 (a) A = mortar (1)B = stirrer/stirring rod (1) not thermometerC = tripod (1)D = Bunsen Burner (1) [4]

(b) filtration [1]

(c) D or description [1]

2 (a) because precipitate formed/goes cloudy (1)sulphur (1)/turbid [2]

(b) reference to fair test/comparison/same depth [1]

(c) sodium thiosulphate/water 1st/2nd acid, last [1]

(d) (i) all points correct (3), -1 for any incorrectsmooth line (1)label (1) [5]

(ii) line lower down (1)does not touch other line (1) [2]

(e) times would be longer (1) because solution more spread out/reference tosurface area/depth (1) [2]

3 Table of resultscorrect burette readings in table (3) or 17.2, 18.9, 26.5

i.e. 16.8, 17.1 and 25.5Differences correctly completed (1) Difference 7.6

i.e. 8.4 [4](a) (i) Experiment 1 [1]

(ii) twice volume/more than twice as much [1](iii) Solution B was 2x (1) concentration of C (1) or similar [2]

B more concentrated than C (1 only)(iv) volume A = 33.6 (1) cm3 (1)/34.4cm3

2x iodine produced (1) [3]

(b) reference to accuracy (1) indicator (1)/easier to see [2]not test for I2 max 2

4 (c) effervescence/fizz/bubbles (1)limewater milky (1)/blue solution [2]

(d) (ii) blue (1) precipitate (1)royal/dark blue (1) solution (1) [4]

(e) (i) white (1) precipitate (1)dissolves (1) [3]

(ii) white (1) precipitate (1)dissolves (1) [3]

(f) Solid D is a sulphate (1) hydrated (1) [2]

(g) copper (1)/Cu2+ (2) [2]




5 (a) (i) Smooth line graph [1](ii) result at 5 minutes (1)

not on curve (1)/gas escapes, gone down [2]

(b) 0.8 g [1]

(c) reference to leak/loss of gas (1)� volumes lower (1) [2]

6 Known mass of beach sand (1)add excess (1) dilute hydrochloric acid (1)filter (1) wash (1) dry (1) residueand weigh sand (1) working out result (1)

max 6 of 8 [6]

[Total: 60]

Grade thresholds taken for Syllabus 0620 (Chemistry) in the June 2003 examination

minimum mark required for grade:maximummark

availableA C E F

Component 1 40 - 26 20 17

Component 2 80 - 52 36 27

Component 3 80 53 31 - -

Component 5 40 31 24 18 14

Component 6 60 42 32 21 15

The threshold (minimum mark) for B is set halfway between those for Grades A and C.The threshold (minimum mark) for D is set halfway between those for Grades C and E.The threshold (minimum mark) for G is set as many marks below the F threshold as the Ethreshold is above it.Grade A* does not exist at the level of an individual component.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the June 2004 question papers

0620 CHEMISTRY

0620/01 Paper 1 (Multiple Choice), maximum mark 40

0620/02 Paper 2 (Core), maximum mark 80

0620/03 Paper 3 (Extended), maximum mark 80

0620/05 Paper 5 (Practical), maximum mark 40

0620/06 Paper 6 (Alternative to Practical), maximum mark 60

These mark schemes are published as an aid to teachers and students, to indicate the requirements of the examination. They show the basis on which Examiners were initially instructed to award marks. They do not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the Examination.

• CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the June 2004 question papers for most IGCSE and GCE Advanced Level syllabuses.


Grade thresholds taken for Syllabus 0620 (Chemistry) in the June 2004 examination.

minimum mark required for grade: maximum mark

available A C E F

Component 1 40 - 26 20 17

Component 2 80 - 52 36 27

Component 3 80 53 31 - -

Component 5 40 31 24 18 14

Component 6 60 42 32 21 15

The threshold (minimum mark) for B is set halfway between those for Grades A and C. The threshold (minimum mark) for D is set halfway between those for Grades C and E. The threshold (minimum mark) for G is set as many marks below the F threshold as the E threshold is above it. Grade A* does not exist at the level of an individual component.

June 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 40


CHEMISTRY (Multiple Choice)


Chemistry – June 2004 0620 01

© University of Cambridge International Examinations 2004

Question Number Key

Question Number

Key

1 A 21 C

2 D 22 C

3 B 23 B

4 B 24 D

5 C 25 D

6 C 26 A

7 A 27 B

8 D 28 B

9 A 29 C

10 D 30 C

11 A 31 D

12 B 32 A

13 B 33 A

14 D 34 B

15 C 35 A

16 D 36 D

17 B 37 A

18 C 38 D

19 A 39 B

20 A 40 A

June 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 80


CHEMISTRY


Chemistry - June 2004 0620 02


1 (a) B, C, F (all needed); [1] Only contain one type of atom [1] NOT: contain one kind of molecule NOT: cannot be split using chemical means (b) C [1] (c) (i) B [1] (ii) any gas with diatomic molecules e.g. chlorine, hydrogen, hydrogen chloride [1] (d) (i) F [1]

(ii) pencil ‘leads’/in pencils/lubricant/in electrical conductors/for electrodes/ in tennis racquets/in golf clubs/hockey sticks etc [1] (e) (i) substance containing 2 or more different atoms combined/bonded/joined (both parts needed for mark) [1] ALLOW: elements (chemically) combined (ii) methane [1] (f) (i) 8 electrons round chlorine and bonded pair with dot and cross = 2 [2] ALLOW: all dots or all crosses Correct number of electrons but bonded pair not clearly on overlap = 1 NOT: molecules other than hydrogen chloride (ii) covalent [1] (iii) blue litmus; [1] (litmus) turns red [1] (iv) pH2 [1] (v) 2 [1] (vi) magnesium chloride [1] NOT: formula Total = 17 2 (a) insoluble particles/solids/dirt trapped/caught on stones; [1] NOT: filter reacts with insoluble impurities NOT: impurities unqualified Water passes through/filtered OWTTE [1] (b) (i) kill bacteria/germs, disinfect water OWTTE [1] (ii) neutralises acidity/water [1] ALLOW: reacts with acids in water (iii) calcium hydroxide [1] NOT: formula (iv) neutralising acid soils/neutralising acidic (industrial) waste/making bleaching powder/removing acidic gases/in Solvay process/in recovery of ammonia/making limewater/in water softening/for making plaster/for making mortar/controlling soil acidity [1] NOT: neutralising acids unqualified NOT: making cement




(c) (i) 100; [1] °C (conditional on 100) [1] (ii) anhydrous cobalt chloride/anhydrous copper sulphate (or correct colours); [1] NOT: cobalt chloride/copper sulphate unqualified Turns pink/blue (respectively) [1] (iii) any suitable e.g. washing/cleaning/drinking/cooking [1] (d) B [1] (e) ethanol [1] NOT: alcohol (f) potassium hydroxide; hydrogen [1] NOT: symbols Total = 15

3 (a) means of measuring gas volume e.g. gas syringe/measuring cylinder (must be graduated); [1] flask/test tube/vessel with calcium carbonate + acid leading to syringe etc IGNORE: lack of reference to closed system (unless drawing incorrect) [1]

record volume on gas syringe/measuring cylinder/measure how much carbon dioxide given off [1]

at various time intervals/at a particular time [1] OR flask/vessel with calcium carbonate and hydrochloric acid in flask (1) measure its mass at beginning of experiment (1) measure mass of flask and contents during reaction (1) at specific time(s) (1) (b) (i) faster/greater/speeds up [1] (ii) slower/less [1] (iii) faster/greater/speeds up [1] (c) (i) add aqueous sodium hydroxide; [1] white precipitate; [1] insoluble in excess [1] (incorrect reagent = 0) ALLOW: flame test - brick red (d) (i) high in the reactivity series/very reactive [1] (ii) 2 electrons in outer shell; [1] inner shells correct as 2.8.8 [1] Total = 13




4 (a) ethanol - solvent ethene - polymer bitumen - roads [3] (b) ethanol [1] (c) (i) C [1] (ii) A [1] (iii) B [1] (iv) D [1] (d) (i) (compound) containing only carbon and hydrogen [1] NOT: it contains carbon and hydrogen (ii) has only single bonds/ has general formula CnH2n+2 [1] NOT: it is saturated Total = 10 5 (a) chlorine, argon, potassium, bromine, iodine [1] ALLOW: symbols (b) chlorine, potassium, argon, bromine, iodine [1] ALLOW: symbols (c) 2

nd box down ticked [1]

(d) chlorine, bromine, iodine (all 3 needed) [1] ALLOW: symbols (e) (i) potassium/K [1] (ii) argon/Ar [1] (f) 1

st and 4

th boxes ticked (1 mark each) [2]

(g) (i) high (boiling point) [1] (ii) conducts/is high [1] (h) potassium loses an/one electron/loses outer shell [1] chlorine gains an/one electron/outer shell becomes complete [1] ALLOW: (for 1 mark) potassium loses two electrons + chlorine gains two electrons ALLOW: e.g. 2.8.8.1 → 2.8.8 for first mark Any indication of sharing electrons = 0 Total = 12




6 (a) carbon monoxide [1] (b) iron oxide loses oxygen/it loses oxygen/oxidation number of iron decreases [1] ALLOW: iron gains electrons Answer must refer to the iron/iron oxide - therefore: NOT: carbon monoxide gains oxygen NOT: oxygen lost in the reaction NOT: iron loses oxygen (c) 3; 2 (one mark each) [2] (d) (i) oxidise the impurities/oxidise Si or P or C/burn off the impurities [1] NOT: get rid of impurities NOT: slag formation (ii) exothermic [1] (iii) is/floats above the molten iron [1] (iv) calcium oxide [1] (v) stronger/harder/not brittle/less easily corroded ORA e.g. iron rusts [1] NOT: less corrosive (e) any 3 of: high melting/boiling points; have coloured compounds (NOT: they are coloured); have high densities; form complex ions; elements/compounds are good catalysts; form ions with different charges/variable oxidation states [3] (f) alloys [1]

Total = 13

Grand Total = 80

June 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 80


CHEMISTRY Extended




• When the name of a chemical is demanded by the question, a correct formula is usually acceptable. When the formula is asked for, the name is not acceptable.

• When a word equation is required a correct symbol equation is usually acceptable. If an equation is requested then a word equation is not usually acceptable.

• An incorrectly written symbol, e.g. NA or CL, should be penalised once in a question.

In the mark scheme if a word or phrase is underlined it (or an equivalent) is required for the award of the mark. (......) is used to denote material that is not specifically required. OR designates alternative and independent ways of gaining the marks for the question. or indicates different ways of gaining the same mark. COND indicates that the award of this mark is conditional upon a previous mark being gained.

• Unusual responses which include correct Chemistry that answers the question should always be rewarded - even if they are not mentioned in the mark scheme.

• All the candidate's work must show evidence of being marked by the examiner.




1. (a) (i) portable [1] (ii) oxygen or air [1] (b) (i) both have four outer or valency electrons [1] need to share four more [1] or need four more to complete energy level NOT four bonds (ii) hard brittle

high melting or boiling point poor conductor of electricity or semi-conductor any TWO [2] NOT insoluble in water, NOT tough NOT appearance (iii) germanium or carbon [1] NOT graphite (c) (i) correctly balanced [1] (ii) lost oxygen [1] or decrease in oxidation number NOT accepts electrons unless valid explanation (iii) 4 oxygen atoms around 1 silicon atom [1] 2 silicon atoms around 1 oxygen [1]

tetrahedral or diagram that looks tetrahedral [1] If some wrong chemistry, such as ionic MAX 2/3

TOTAL = [12] 2. (a) (i) USA or Texas or Poland or Mexico or Japan or Ethiopia

Australia or Sicily [1] accept other sources of sulphur eg petroleum

or natural gas or metal sulphides or volcanoes NOT coal, NOT underground

(ii) Preserving food or bleaching or sterilising or

disinfecting or making paper or bleaching wood pulp or wine or jam or fumigation or making paper [1]

NOT making wood pulp (iii) burnt/roast in oxygen or air [1] (iv) vanadium(V) oxide or vanadium oxide or platinum [1]

ignore oxidation state of vanadium

(v) Increase temperature (increases rate) but reduces yield [1] catalyst only increases rate or a catalyst does not

influence position of equilibrium [1] NOT a definition of a catalyst (vi) sulphur trioxide + sulphuric acid = oleum [1] correct symbol equation acceptable (vii) H2S2O7 + H2O = 2H2SO4 [1]




(b) (i) potassium [1] (ii) ammonium sulphate [1] (iii) Ca3(PO4)2 [1] Ca(H2PO4)2 [1] (iv) only acceptable responses are:

accepts a proton [2] accepts H

+ [1] only

TOTAL = [14] 3. (a) dissolved or solution in water [1]

NOT aqueous NOT soluble in water l liquid and g gas [1]

(b) 6 electrons in bond between two nitrogen atoms [1] 2 electrons on each nitrogen [1] ignore any coding of electrons with dots or crosses (c) (i) decreases or reaction stops or rate becomes zero [1] (ii) concentration or number of effective collisions [1] decreases [1] used up or less chemical or less collisions etc [1] only (iii) greater initial slope [1] same final point [1] as long as new curve touches the original curve near

the top allocate the mark

(iv) greater surface area [1]

TOTAL = [10] 4 (a) (i) Named soluble zinc salt [1] corresponding sodium salt [1] If hydroxide or oxide then 0/2 (ii) Correct equation [2] not balanced [1] only (iii) Correct equation [2] (b) (i) Fe

3+ + 3OH

- = Fe(OH)3 [1]

(ii) Max at 8cm

3 [1]

Same shape of graph

Just the above shape, the height of the precipitate and the volume of sodium hydroxide are irrelevant [1]




(iii) Maximum then height of precipitate decreases [1] or graph slopes down to x axis or comes to zero hydroxide dissolves in excess or it is amphoteric [1]

TOTAL = [11]

5. (a) Has to be three different uses.

any use that depends on malleability or ductility- jewellery, pipes, wires, sheets, roofing, ornaments [1]

NOT that it is malleable or ductile

electrical wires or cooking utensils or electrodes [1] (good) conductor

making alloys or named alloy [1] (b) (i) Cu

2+ + 2e = Cu [1]

(ii) gas is oxygen [1] (copper(II) sulphate) changes to sulphuric acid [1] or copper ions removed from solution (c) (i) copper atoms - electrons = copper ions [1] accept correct symbol equation (ii) concentration of copper ions does not change or [1] amount or number of copper ions does not change

copper ions are removed and then replaced [1] or copper is transferred from anode to cathode

(iii) refining copper or plating (core) [1]

or extraction of boulder copper

TOTAL = [10] 6. (a) (i) correct repeat unit [1] COND evidence of polymer chain [1] (ii) glucose or maltose [1] (iii) addition (polymerisation) or no other product

except polymer [1] condensation (polymerisation) or polymer

and water [1] (b) (i) sodium hydroxide [1] COND ammonia or alkaline gas or litmus red to blue [1] If aluminium added wc =0




(ii) measure pH [1] more than 1 and less than 7 or

correct colour eg orange or yellow NOT red NOT green [1]

OR add magnesium or calcium carbonate [1] weak acid reacts slowly

(c) (i) ethyl acrylate [1] ester or alkene [1] (ii) brown to colourless (NOT clear) [1] correct formula for acid NOT ester [1]

TOTAL = [13] 7 (a) Avogadro’s Number of particles

or formula mass in grams or 6 x 10

23 particles accept atoms, ions and molecules

or as many particles as there are carbon atoms in 12.00g of 12

Ca ANY one [1]

(b) (i) moles of Mg = 3/24 = 0.125

moles of CH3COOH = 12/60 = 0.200 magnesium is in excess OR 3.0g of magnesium react with 15g of acid only 12.0 g of acid present

magnesium is in excess [3] (ii) Mark conseq to (i) but NOT to any simple integer moles of H2 = 0.1 [1] (iii) Mark conseq to (ii) but NOT to any simple integer Volume of hydrogen = 0.1 x 24 = 2.4 dm

3 [2]

(c) (i) moles of NaOH = 25/1000 x 0.4 = 0.01 [1] (ii) Mark conseq to (i) but NOT to any simple integer moles of acid = 0.01/2 = 0.005 [1] (iii) Mark conseq to (ii) max 10M concentration of acid = 0.005 x 1000/20 [1] = 0.25 mol/dm

3 [1]

TOTAL = [10] TOTAL for PAPER = [11] + [14] + [10] + [11] + [10] + [13] + [11] = [80]

June 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 40


CHEMISTRY Practical




1 Table of results Experiment 1 Temperature boxes completed

Increasing Comparable to supervisor

1 1 1

[3] Experiment 2 Temperature boxes completed

Decreasing Comparable to supervisor

1 1 1

[3] (a) All points plotted correctly

(-1 for each incorrect) Smooth line graphs Labelled

4

2 1

[7] (b) (i) 1. Value from graph 1 2. Value from graph ± 0.25

No unit only (1) 1 [2]

(ii) 1. Exothermic

2. Endothermic 1 1

[2]

(c) Fizz/bubbles/effervescence

Solid disappears 1 1

[2]

(d) Carbonate

Fizz with acid or similar 1 1

[2]

(e) Solid A – value from table/room temperature ± 3˚C

Solid B – value from table/room temperature Reaction finished

1 1 1

[3] Sub Total [24]

2 (a) White 1 [1] (c) (i) White

Precipitate 1 1

[2]

Excess – no change 1 [1] (ii) No precipitate/change 1 [1] (iii) Paper goes blue

Fizz/bubbles etc Reference to smell

1 1 1

[3] (iv) pH greater than 7 1 [1] (v) Milky/cloudy 1 [1] (d) Calcium 1 [1] (e) Ammonia 1 [1]




(f) Limewater

Carbon dioxide 1 1

[2]

(g) Nitrate

Hydroxide 1 1

[2]

Sub Total [16] Total [40]

June 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 60


CHEMISTRY

Alternative to Practical


IGCSE – June 2004 0620 6


1 (a) A Funnel B Flask C (Teat) Pipette/dropper

1 1 1

[3] (b) Increase surface area

Reference to rate/efficiency/easily 1 1

[2]

(c) pH may be different/vary at different places/fair test 1 [1] (d) Reference to plants/crops growth

No plants 1 0

[1]

2 (a) First 4

Second 3

1

[1] (b) Water and air/oxygen necessary for rusting

Statement referring to any tube e.g. no water and air in tube 1/2 1 1

[2]

3 (a) Bulb lights up/silver liquid/metal formed/bubbles/fizz/lead x 1 [1] (b) (i) Suitable material e.g. carbon/graphite/steel/Pt/Ag/An 1 [1] (ii) Indication on diagram of cathode 1 [1] (c) Bromine/Br2

Anode/positive 1 1

[2]

(d) Reference to toxicity of bromine/lead/lead bromide

NOT harmful/dangerous 1 [1]

4 Experiment 1 Temperatures correct

(-1 any incorrect) 2 [2]

Time/Min 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Temp/˚C 22 24 26 28 29 30 30 29 28 27 26 Experiment 2 Temperatures correct

(-1 any incorrect) 2 [2]

Time/Min 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Temp/˚C 21 19 17 15 14 13 13 14 15 16 17 (a) Graph. Points plotted correctly

(-1 each incorrect) Smooth lines/curves Labelled

3

2 1

[6] (b) (i) Temperature from graph 29.5˚C

± 0.25˚C Temperature from graph 13.5˚C

1

1

[2] (ii) 1. Exothermic

2. Endothermic 1 1

[2]

(c) Carbonate

Fizz/gas with acid 1 1

[2]


IGCSE – June 2004 0620 6


(i) 22˚C 21˚C

(d)

(ii) Reference to room temperature/reaction finished No units only (1)

1 1 1

[3]

5 (a) (i) White Precipitate

1 1

[2]

No change/white precipitate/insoluble in excess 1 [1] (ii) No/thin precipitate/no reaction 1 [1] (b) Ammonia 1 [1] (c) Reference to limewater/test for carbon dioxide 1 [1] (d) Nitrate

Alkali/hydroxide/oxide 1 1

[2]

6 (a) Indication of copper oxide 1 [1] (b) Black

to red/pink/brown

1

1

[2] (c) To cool/condense

Steam/water 1 1

[2]

7 (a) Anhydrous copper sulphate/cobalt chloride

Goes blue/pink in water, no change for ethanol 1 1

[2]

(b) Add indicator/named indicator or CO3

2-/Mg Turns red/correct colour in acid, no change for sodium sulphate

1 1

[2]

(c) Add silver nitrate

White precipitate with hydrochloric acid, no change with nitric acid 1 1

[2]

8 Add known mass of manganese oxide

To (measured volume of) hydrogen peroxide Bubbles Test gas with glowing splint Result Filter Dry solid Reweigh and compare (max 6)

1 1 1 1 1 1 1 1

[6] Total for Paper [60]



MARK SCHEME for the June 2005 question paper

0620 CHEMISTRY 0620/01 Paper 1 (Multiple Choice), maximum mark 40

Mark schemes must be read in conjunction with the question papers and the Report on the

Examination.

• CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the June 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses’.


Grade thresholds for Syllabus 0620 (Chemistry) in the June 2005 examination.


available A C E F

Component 1 40 34 24 18 15


JUNE 2005

IGCSE

MARK SCHEME

MAXIMUM MARK: 40


Chemistry Paper 1 (Multiple Choice)


IGCSE – JUNE 2005 0620 1


Question Number

Key Question Number

Key

1 C 21 C

2 B 22 A

3 B 23 B

4 C 24 A

5 A 25 A

6 A 26 C

7 C 27 B

8 A 28 D

9 D 29 B

10 D 30 B

11 D 31 B

12 C 32 C

13 A 33 B

14 C 34 A

15 B 35 D

16 D 36 C

17 B 37 A

18 B 38 A

19 D 39 A

20 D 40 D




0620 CHEMISTRY 0620/02 Paper 2 (Core Theory), maximum mark 80

This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which Examiners were initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the

Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the

Examination.

• CIE will not enter into discussion or correspondence in connection with these mark schemes.

CIE is publishing the mark schemes for the June 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.




available A C E F

Component 2 80 N/A 57 42 31


June 2005

IGCSE

MARK SCHEME

MAXIMUM MARK: 80


CHEMISTRY (Core Theory)


IGCSE – JUNE 2005 0620 2


1 (a) (i) A [1] (ii) B + E [1] (iii) A + C [1] (iv) B [1] (v) B + E [1] (b) (i) graphite [1] NOT: charcoal (ii) diamond/buckminsterfullerene [1] NOT: graphite (but ALLOW: ecf from part (i) (c) NaI [1] ALLOW: Na+

I-

NOT: Na+ + I- (d) compound (no mark) because two different (types of) atoms joined/bonded etc. [1] ALLOW: two different elements bonded NOT: atoms together Total = 9 2 (a) filtering/filtration [1] NOT: distillation, NOT: decanting (b) litmus turns pink/red [1] NOT: orange (c) (i) steel [1] (ii) water [1] NOT: steam (iii) copper/iron [1] (iv) natural gas [1] NOT: methane (d) methane [1] (e) 100o C (100 = 0) [1] (f) (i) calcium/Ca2+ [1] (ii) e- [1] ALLOW: e NOT: electron (g) (i) carbon dioxide + water [1] ACCEPT: correct formulae


IGCSE – JUNE 2005 0620 2


(ii) carbon monoxide [1] NOT: CO Total = 12 3 (a) random arrangement; far apart. [2] (b) pH9 [1] (c) (i) NH3/H3N [1] (ii) covalent [1] (iii) weak forces between particles OR molecules/weak intermolecular forces [1] (d) (i) H2SO4 [1] (ii) nitrogen; soil [2] (e) Any 3 from:

ammonia evaporates from (ammonia) solution; diffusion; particles/molecules of ammonia/gases are in constant movement/ move freely; ALLOW: move fast NOT: particles of ammonia solution move freely NOT: move from high to low concentration movement of particles/molecules is random. [3] NOT: ammonia spreads out;

(f) (i) the air [1] ALLOW: atmosphere (ii) 2 (NO2) [1] (iii) reversible reaction [1] ALLOW: equilibrium (iv) exothermic/heat given out [1] Total = 16 4 (a) monomers [1] (b) does not have a double bond/only contains single bonds/has a single C – C bond [1] NOT: has a single bond NOT: it is saturated NOT: no spare bonds (c) displayed/graphical formula correct [1] ALLOW: correct dot and cross diagrams (d) (i) breaking down of long-chained hydrocarbons/formation of smaller hydrocarbons from larger [1]


IGCSE – JUNE 2005 0620 2


(ii) high temperature [1] ALLOW: heat (catalyst alone = 0) (iii) C8H18 [1] ALLOW: other sensible combinations 2(C2H4) + C6H14 (e) (i) H2 [1] (ii) any 2 of:

temperature gradient in fractionation column; smaller/lighter molecules (rise) higher in column OR smaller/lighter molecules more easily vaporised OR e.g. referring to larger/heaver molecules ALLOW: hydrocarbons in place of molecules NOT: lighter/heavier fractions different fractions condense at particular heights in column/fractions condense when temperature falls below their boiling points [2] ALLOW: different fractions have different boiling points/condense at different temperatures

(iii) petrol: fuel (for cars)/other suitable use [1] NOT: for cars etc. lubricating fraction: lubricating oils/waxes/polishes/other suitable use [1] NOT: for planes etc.

Total = 11 5 (a) (i) molecule containing 2 atoms [1] ALLOW: element containing 2 atoms (ii) whether it is solid, liquid or gas (all 3 needed) [1] (b) (i) gas; liquid; solid (all 3 = 2 marks; 2 correct = 1 mark) [2] (ii) red/brown/orange or combination of these [1] (iii) 130-210 (o C) (actual = +184 o C) [1] (c) iodine + potassium chloride (1 each) [2] (d) (i) 8 electrons in each shell + atoms joined no bonding electrons = 1 [2] IGNORE: inner shell electrons if correct (incorrect inner shell electrons = 1 max) (ii) water purification OR treatment/killing bacteria etc./bleaching agent (for paper)/

making refrigerants/making organic chlorine compounds (named)/making solvents/extracting titanium/detinning scrap tinplate/making hydrochloric acid/extraction of bromine from seawater/other suitable use [1]


IGCSE – JUNE 2005 0620 2


(e) (i) A [1] (ii) C [1] (iii) it contains ions; which can move/are free to move (OWTTE) [2] reference to electrons = 0 (f) (i) Period 6 [1] (ii) 85 [1] (iii) atoms with (same number of protons and) different number of neutrons/ different mass number/different nucleon number [1] NOT: molecules with… ALLOW: elements with…. (iv) 125 [1] Total = 19 6 (a) (i) iron + sulphuric acid → iron sulphate + hydrogen [2] -1 per error/omission NOT: iron(III) sulphate NOT: hydrogen sulphate (ii) lighted splint; pop/small explosion etc. [2] (consequential marking) (b) (i) cathode [1] (ii) allows conduction (of electricity)/allows charges or ions to flow through the solution [1] (iii) gains layer of copper/coated with copper NOT: gets bigger [1] decreases in size/gets smaller/loses copper etc. [1] ALLOW: the copper dissolves NOT: breaks up/flakes off (iv) aqueous sodium hydroxide; light blue ppt; insoluble in excess OR aqueous ammonia; light blue ppt; soluble in excess/forming dark blue solution [3] (consequential marking) (c) to make them attractive/makes them shiny/protects the iron so it does not rust/does

not corrode OR oxidise easily/less reactive than iron [1] NOT: chromium is unreactive etc. NOT: other properties of chromium e.g. hard NOT: corrosive (d) iron > chromium > copper [1] Total = 13




0620 CHEMISTRY 0620/03 Paper 3 (Extended Theory), maximum mark 80

This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which Examiners were initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the

Examination.

• CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the June 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.




available A C E F

Component 3 80 58 30 16 11


June 2005

IGCSE

MARK SCHEME

MAXIMUM MARK: 80


CHEMISTRY Extended Theory


IGCSE – JUNE 2005 0620 3


1 (a) (i) darker or actual colours [1] chlorine yellow, yellow/green bromine orange, brown, brownish red iodine black grey, purple (ii) gas, liquid, solid [1] all three needed (iii) colourless or (pale) yellow [1] gas [1] (b) Must have a correct reagent otherwise wc = 0 add chlorine water or bubble in chlorine gas [1] yellow or orange or brown [1] dark brown or grey crystals (Accept colour that is darker than for bromide) [1] OR add (acidified) silver nitrate(aq) [1] off white or pale yellow or cream precipitate or soluble in aqueous ammonia [1] yellow precipitate insoluble in aqueous ammonia [1] precipitate essential then either colour or solubility in aqueous ammonia OR add lead nitrate(aq) [1] pale yellow or off white or cream precipitate [1] yellow precipitate insoluble in aqueous ammonia [1] Accept any test that could work – electrolysis, iron(III) salt

bromine, potassium dichromate, potassium manganate(VII) etc. (c) I2 + 3Cl2 = 2ICl3 [2] For having either reactants or products correct ONLY [1] (d) chlorine [1] COND lower Mr or lower density or lighter molecules or molecules move faster [2] OR lighter or based on Ar MAX [1] smaller with no additional comment or sieve idea [0] N.B. a total of [3] not [2] TOTAL = 12 2 (a) Zn + I2 = Zn2+ + 2I

- [2] For having either reactants or products correct ONLY [1] (b) for zinc and sodium hydroxide white precipitate [1] dissolves in excess (only if precipitate mentioned) [1] for zinc and ammonia same results [1] Mark either first (sodium hydroxide or aqueous ammonia), if completely correct, then an

additional [1] can be awarded for stating that the other has the same results.


IGCSE – JUNE 2005 0620 3


(c) (i) zinc and a reason [1] Do not mark conseq to iodine in excess (ii) final mass of zinc bigger or the level section higher or less zinc used up [1] gradient less steep or longer time or falls more slowly [1] (iii) steeper gradient [1] same loss of mass of zinc [1] TOTAL = 10 3 (a) (i) CH3-CH==CH2 [1] (ii) conseq to (i) correct repeat unit [1] COND evidence of continuation [1] (iii) monomer [1] COND because it has a double bond or unsaturated or alkene [1] NOT addition (b) (i) to remove fibres or remove solid NOT precipitate, NOT impurities, NOT to obtain a filtrate [1] (ii) because silver atoms have lost electrons [1] OR oxidation number increased (iii) silver chloride [1] (c) (i) name of an ester [1] formula of an ester [1] if they do not correspond MAX [1] Accept name - terylene for formula ester linkage and continuation If a ‘fat’ complete structure must be correct e.g. C17H35 etc. Mark for formula only - [1] (ii) alcohol or alkanol [1] NOT a named alcohol (d) (i) acid loses a proton [2] base accepts a proton [1] OR same explanation but acid loses a hydrogen ion (1) and base gains hydrogen ion (1) (ii) only partially ionised or poor hydrogen ion donor or poor proton donor [1] NOT does not form many hydrogen ions in water or low concentration of hydrogen

ions NOT pH TOTAL = 15


IGCSE – JUNE 2005 0620 3


4 (a) (i) correct word equation (carbon dioxide and water) [1] Accept correct symbol equation

(ii) Must have a correct reagent otherwise wc = 0 add (acidified) barium chloride(aq) or nitrate or add barium ions [1] COND white precipitate [1] NOT lead(II) compounds (iii) low pH or universal indicator turns red(aq) [1] pH 3 or less (b) (i) H2S + 2O2 = H2SO4 [2] unbalanced [1] (ii) unpleasant smell or it is poisonous or when burnt forms acid rain or forms sulphur

dioxide or forms sulphuric acid [1] NOT it is a pollutant (iii) 2H to 1S COND 8e around sulphur atom 2e per hydrogen atom THREE correct [2] TWO from above [1] Ionic structure = [0] (c) (i) vanadium oxide or vanadium(V) oxide or vanadium pentoxide or V2O5 Must be correct oxidation state if one given [1] (ii) 400 to 500o C [1] (iii) add to (concentrated) sulphuric acid NOT dilute [1] COND (upon sulphuric acid) above then add water [1] (d) mass of one mole of CaSO4 = 136 moles of CaSO4 in 79.1g = 0.58 accept 0.6 [1] moles of H2O in 20.9 g = 1.16 accept 1.2 [1] conseq x = 2 x given as an integer [1] TOTAL = 16

5 (a) (i) A is glutamic acid [1] B is alanine [1] Accept names only, NOT Rf values

(ii) because acids are colourless or to make them visible [1] or to show positions of the samples or distance travelled

(iii) compare with known acids or reference samples or standards [1] Accept from colours of samples

(iv) amide linkage [1] COND different monomers [1] continuation [1] Accept hydrocarbon part of chain as boxes If nylon 6 then only one monomer [1] NOT different monomers


IGCSE – JUNE 2005 0620 3


(b) correct structure as syllabus (box representation) correct linkage --O-- [1] continuation [1] (c) (i) C6H12O6 = 2C2H5OH + 2CO2 [2] not balanced [1] Accept C2H6O (ii) gives out energy or equivalent [1] NOT heat N.B. a total of [1] not [2] (iii) glucose used up or yeast ‘killed’ by ethanol [1] NOT yeast used up NOT reactant used up (iv) oxidise alcohol to acid or to ethanoic acid [1] or to carbon dioxide and water or if oxygen present aerobic respiration or cannot have anaerobic respiration in presence of oxygen NOT it is anaerobic respiration, must be additional comment (v) fractional distillation [1] TOTAL = 15 6 (a) (i) bauxite [1] (ii) to reduce melting point or improve conductivity [1] or as a solvent or reduce the working temperature (iii) carbon dioxide or monoxide or fluorine [1] (b) (i) aluminium [1] (ii) solution goes colourless or copper formed [1] or a brown solid forms or blue colour disappears or bubbles NOT goes clear or copper formed (iii) covered with an oxide layer [1] (c) reaction no reaction [1] reaction reaction [1] (d) (i) 2Al(OH)3 = Al2O3 + 3H2O [2] Not balanced [1] (ii) Aluminium nitrate = aluminium oxide + nitrogen dioxide + oxygen [2] only TWO correct products [1] TOTAL = 12




0620 CHEMISTRY 0620/05 Paper 5 (Practical Test), maximum mark 40


Examination.





available A C E F

Component 5 40 32 26 19 16


June 2005

IGCSE

MARK SCHEME

MAXIMUM MARK: 40


CHEMISTRY

Practical Test


IGCSE – JUNE 2005 0620 5


1 Table of results

Experiment 1

Initial and final volume boxes correctly completed (1) To 1 d.p. (1) Comparable to Supervisor ± 4 (1) [3]

Experiment 2

Initial and final volume boxes correctly completed (1) To 1 d.p. (1) Comparable to Supervisor ± 4 (1) [3]

(a) white/cloudy/milky (1) [1]

(b) purple/pink (1) to colourless (1) [2]

(c) neutralisation (1) [1]

(d) (i) Experiment 2 (1) [1]

(ii) Experiment 2 more/greater volume (1) x 2 (1) [2]

(iii) M more concentrated/stronger than N (1) x 2 (1) [2]

(e) 2 x value from table (1) cm3 (1)

twice as much calcium hyrdroxide (1) [3]

(f) e.g. use a pipette/burette instead of a measuring cylinder (1) [1]

(g) slightly (1) [1]

Sub total 20

2 (a) colourless (1) reference to smell (1) [2]

(b) red/orange/yellow (1) 4 to 6 ± 1 (1) see Supervisor [2]

(c) (i) fizz/bubbles (1) lighted splint (1) pops (1) [3]

(ii) fizz/bubbles (1) limewater milky/cloudy (1) [2]

(iii) green/blue (1) deep/dark blue (1) [2]

(iv) colourless/no change/oily layer (1) sweet/fruity/glue/smell (1) [2]

(v) orange/no change (1) [1]

(d) (i) hydrogen (1) [1]

(ii) carbon dioxide (1) [1]

(e) copper (1) 2+ (1) [2]

(f) weak (1) acid (1) check (b) for consequential answer [2] Sub total 20 Total 40




0620 CHEMISTRY 0620/06 Paper 6 (Alternative to Practical), maximum mark 60


Examination.





available A C E F

Component 6 60 48 38 27 22


June 2005

IGCSE

MARK SCHEME

MAXIMUM MARK: 60


CHEMISTRY



IGCSE – JUNE 2005 0620 6


1 (a) boxes completed retort/clamp stand (1) (teat) pipette/dropper (1) Bunsen burner (1) [3] (b) hydration/exothermic (1) [1] 2 (a) electrodes correctly labelled on rods (1) [1] (b) bubbles at positive electrode (1), bubbles at negative electrode (1) bulb lights up/smells of bleach/greenish gas (1) [3] (c) (i) chlorine (1) [1] (ii) litmus/indicator (1) bleached/colourless (1) [2] 3 volumes from syringe diagrams; 15, 45, 61, 73, 74, 80 and 80 all correct (4) (-1 for each incorrect) [4] (a) graph: all points plotted correctly (3) (-1 for each incorrect) smooth curve (1) [4] (b) volume of acid from graph, 10.5 → 11.5 (1) [1] (c) volume of hydrogen from graph, 29.5 → 30.5 (1) [1] 4 table of results: all initial and final volume boxes correctly completed 0.0, 10.6, 14.9 36.1 (3) difference boxes correctly completed, 10.6, 21.2 (1) [4] (a) neutralisation (1) [1] (b) (i) experiment 2 (1) [1] (ii) experiment 2 more/greater volume (1) x 2 (1) [2] (iii) M more concentrated/stronger than N (1) x 2 (1) [2] (c) 21.2 (1) cm3 (1) twice as much calcium hydroxide (1) [3] (d) e.g. use a pipette/burette instead of a measuring cylinder (1) [1] 5 (b) (i) fizz/bubbles (1) pops (1) [2] (ii) fizz/bubbles (1) limewater milky (1) [2] (c) weak (1) [1]


IGCSE – JUNE 2005 0620 6


(d) (i) hydrogen (1) [1] (ii) carbon dioxide (1) [1] (e) copper (1) 2+ (1) [2] 6 (a) no/little water present/little water implied (1) [1] (b) any value less than 7 (1) [1] (c) chromatography (1) apply to paper (1) use of solvent (1) description of two yellow spots (1) [4] paper in drink = max 2 7 (a) straight line (1) DRAWN WITH A RULER [1] (b) inaccurate point is at pH 5 (1) not on line (1) [2] (c) % corrosion decreases as pH increases (1) [1] 8 same amount/measured volume of peroxide (1) add known mass of metal oxide (1) time (1) measure volume of oxygen (1) repeat with other oxide (1) compare/conclusion (1) [6] method will not work = 0

Total 60



MARK SCHEME for the May/June 2006 question paper

0620 CHEMISTRY

0620/01 Paper 1 – Multiple Choice, maximum raw mark 40

These mark schemes are published as an aid to teachers and students, to indicate the requirements of the examination. They show the basis on which Examiners were initially instructed to award marks. Mark schemes must be read in conjunction with the question papers and the Report on the Examination. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session.

• CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2006 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.



IGCSE – May/June 2006 0620 01


Question Number

Key Question Number

Key

1 A 21 A

2 C 22 B

3 C 23 D

4 A 24 B

5 D 25 D

6 B 26 A

7 C 27 A

8 D 28 D

9 C 29 D

10 C 30 A

11 C 31 C

12 A 32 A

13 B 33 A

14 B 34 D

15 D 35 C

16 D 36 A

17 B 37 D

18 B 38 B

19 C 39 C

20 B 40 B




0620 CHEMISTRY

0620/02 Paper 2, maximum raw mark 80

These mark schemes are published as an aid to teachers and students, to indicate the requirements of the examination. They show the basis on which Examiners were initially instructed to award marks. They do not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the

Examination. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session.






1 (a) Substance containing only 1 type of atom/substance which cannot be broken down to any other substance by chemical means [1]

(b) B [1] (c) A + D (both needed) [1] (d) (i) C [1] (ii) carbon [1] (iii) drill bits/ for cutting OWTTE [1] (e) Any 3 of: conducts heat/conducts electricity/malleable/ductile/sonorous/shiny NOT: silvery/high melting OR boiling points [3]

(f) (i) alloy(s) [1] (ii) mild steel → car bodies; stainless steel → chemical plant; aluminium → aircraft ALLOW car bodies; copper → electrical wiring [4] [Total: 14] 2 (a) respiration [1] (b) (i) CH4; O2 (1 mark each) [2] (ii) fuel OWTTE [1] (iii) arrangement: random/not regularly arranged/not ordered/widely spaced OWTTE; motion: moving/random; [2] (iv) alkane(s) [1] (v) C2H6 box – 2nd from left ticked [1] (c) C [1] (d) (i) the bacteria NOT: living things/plants/animals [1] (ii) speeding up of a chemical reaction by a specific substance [1] (e) phosphorus; nitrogen (1 each) [2] [Total: 13]




3 (a) (i) D [1] (ii) A + C (both needed) [1] (iii) B [1] (iv) E [1] (v) C [1] (b) sharing; chlorine; low; diamond; strong [5] (c) (i) 2 electrons paired and two atoms shown [1] (ii) lighted splint; pops/explodes OWTTE [2] [Total 13] 4 (a) (i) hydrogen; [1] (ii) ethene [1] (iii) carbon dioxide [1] (b) (add) bromine water/aqueous bromine ALLOW: bromine: with ethene – decolourises OWTTE; with methane – no reaction/remains orange/brown OWTTE [3] (c) (i) (addition) polymerisation [1] (ii) 4th box from left (last one) ticked [1] (d) cracking ALLOW thermal decomposition [1]

(e) (i) test: add (red) litmus paper; goes blue [2] (ii) 17 [1] (f) sulphur dioxide formed; harmful effect of sulphur dioxide e.g. acid rain/breathing difficulties/ kills fish/leaf drop on trees etc [2] ALLOW: carbon dioxide; global warming ALLOW: carbon monoxide; poisonous [Total: 14]




5 (a) (i) filtration/description of filtration [1] (ii) weakly acidic/2nd box down ticked [1] (b) (i) from the limestone/ from the underlying rocks [1] (ii) carbon dioxide; water (1 each) [2] (c) (i) carbonate/CO3

2– [1] (ii) 20 mg (unit must be present) [1] (iii) nitrate/NO3

– [1] (iv) (aqueous) sodium hydroxide/other suitable hydroxide/ammonia; red-brown/ brown; precipitate [3] IF: ‘soluble in excess’ minus 1 mark (d) carbon dioxide higher (in soil air); nitrogen higher (in soil air); oxygen lower (in soil air); [3] (e) correct formula with all atoms and bonds [1] [Total: 15] 6 (a) haematite; ALLOW other correct named ores [1]

(b) (i) 2:2 [1] (ii) poisonous ALLOW: answers related to reducing oxygen carrying capacity of blood/effect on haem etc [1] (c) (i) iron oxide + carbon monoxide → iron + carbon dioxide [1] (wrong oxidation number(s) = 0)

(ii) reduction [1] (d) (i) (thermal) decomposition [1]

(ii) any suitable e.g. making cement [1] (iii) slag [1]

(e) (i) manganese [1]

(ii) acidic [1] (iii) 6% [1]

[Total: 11]




0620 CHEMISTRY









1 (a) compounds are highly coloured [1] used as catalysts [1] more than one oxidation state [1] Four boxes ticked that include three correct choices [2] Four boxes ticked that include two correct choices [1] Four boxes ticked that include one correct choices [0] Five boxes ticked [0] (b) (i) period 4 [1] (ii) 26p and 30n [1] (c) (i) limestone [1] (ii) slag [1] (iii) iron ore [1] (d) to burn or provide heat [1] to make carbon monoxide [1] (e) mild steel cars or machinery or fridges etc. [1] stainless steel cutlery or chemical plants etc. [1] [TOTAL = 12] 2 (a) X W Z Y [2] For most reactive X and least Y [1] ONLY All other responses [0] (b) magnesium W [1] copper Y [1] (c) (i) goes "pop" with burning splint [1] or mixed with air and ignited goes pop NOT glowing splint (ii) test and observable result [1] universal indicator goes blue or pH paper goes blue or high pH, accept 13, 14 or ammonium ion gives off ammonia or with metallic cations forms a precipitate [1] NOT litmus ONLY accept - neutralises acids with an observable result, e.g. becomes warm. (iii) Group 1 [1] (iv) electrolysis [1] COND molten [1] [TOTAL = 10]




3 (a) ammonia 10 hydrochloric acid 1 sodium hydroxide 13 ethanoic acid 4 All correct [2] Two correct [1] (b) With strong acid bulb brighter [1] faster rate of bubbles [1] OR corresponding comments for weak acid (c) proton NOT hydrogen ion [1] H+ not conditional on proton [1] Only way for [2] is proton and H+ (d) (i) CaO and MgO [1] (ii) CO2 and SO2 [1] (iii) Al2O3 [1] (iv) CO [1] [TOTAL = 10] 4 (a) 4 Ge atoms around 1 Ge [1] Looks tetrahedral or stated to be [1] (b) (i) Graphite has layers [1] COND that can move/slip or weak bonds between layers [1] Graphite has delocalised/free/mobile electrons [1] (ii) property and use [1] soft lubricant or pencils OR good conductor electrodes or in electric motors (c) (i) CO2 and SiO2 or XO2 [1] (ii) CO2 molecular or simple molecules or simple covalent [1] SiO2 macromolecular or giant covalent [1] (d) Ge2H6 [1] [TOTAL = 10]




5 (a) (i) Burn sulphur in air (or oxygen) [1] (ii) as a bleach [1] (iii) kill bacteria/micro-organisms [1] NOT prevents food going bad or rotten or decaying (b) (i) decrease [1] (ii) exothermic [1] COND increase temperature favours back reaction so it is endothermic, so forward reaction must be exothermic [1] OR any similar explanation will be awarded the mark, for example The forward reaction is not favoured by an increase in temperature so it is exothermic (rather than endothermic) (iii) Low enough for good yield [1] High enough for (economic) rate [1] Any similar explanation will be awarded the mark NOT just that it is the optimum temperature (iv) bubble into (conc) sulphuric acid [1]

add water [1] NOT consequential [TOTAL = 10] 6 (a) (i) Any bond that is broken C-H or O=O [1] Bond that is formed C=O or O-H [1] Do not insist on double bonds (ii) More energy is released forming bonds [1]

than is used breaking bonds [1] For just - more energy released than used [1] For - energy is released forming bonds and it is used breaking bonds [1] (b) (i) U [1] 235 [1] (ii) treatment of cancer, autoradiographs, tracer, sterilising food, surgical equipment, measuring thickness, checking welds [1] (c) (i) reductant zinc [1] oxidant hydrogen (ions) [1] (ii) magnesium instead of zinc or increase concentration of acid or copper instead of iron [1]




(iii) sacrificial protection or stop iron/steel rusting [1] or galvanising (d) (i) pink or purple [1] to colourless or decolourised [1] NOT red NOT clear (ii) 2I– – 2e = I2 [2] unbalanced ONLY [1] [TOTAL = 15] 7 (a) (i) any correct equation [1] (ii) structural formulae from but-1-ene, but-2-ene, methylpropene or cyclobutane Any TWO [2] (b) (i) light or 200°C or lead tetraethyl [1]

(ii) substitution or photochemical or chlorination or free radical [1] or halogenation (iii) 1-chlorobutane, 2-chlorobutane, dichlorobutane etc. Any TWO [2] (c) (i) CH3CH2CH2OH or CH3CH(OH)CH3 [1] (ii) CH3CH(Br)CH2Br [1] NOT 1,3-dibromopropane (d) moles of CH3-CH = CH2 reacted = 1.4/42 = 0.033 [1] conseq maximum moles of CH3-CH(I)-CH3 that could be formed = 0.033 [1] conseq maximum mass of 2-iodopropane that could be formed = 5.61 g [1] accept 170 x 0.033 = 5.61 and 170 x 0.033333 = 5.67 conseq unless greater than 100% percentage yield 4.0/5.67 x 100 = 70.5% [1] Do not mark consequently to a series of small integers. There has to be a serious attempt to answer the question, then consequential marking is appropriate. [TOTAL = 13] [For paper 12+10+10+10+10+15+13 = 80]




0620 CHEMISTRY









1 Table of results

Volumes completed for 10 seconds (1) and 20 seconds (1)

Volumes decreasing (1)

Comparable to supervisor (2) [5]

(a) Graph points correctly plotted (2), -1 for each incorrect

Best fit lines (1) labels (1) [4]

(b) fizzing/bubbles/black (1) [1]

(c) (i) Experiment 1 (1) [1]

(ii) strongest/more concentrated solution (1) more collisions (1) [2]

(d) (i) e.g. amount of catalyst added different/starting the timer/inaccurate measurement of peroxide max 2 [2]

(ii) e.g. measure mass of catalyst/time using data logger/use a burette or pipette to measure peroxide max 2 [2]

(e) filter (1) mass of catalyst same before and after (1)

/repeat experiment and compare volumes of gas given off (1) max 2 [2]

Experiment 5

Glowing splint (1) relights (1) oxygen (1) [3]

[Sub total = 22]

2 (a) white (1) [1]

(b) paper goes pink/colourless/condensation description/ solid yellow max 2 [2]

(c) (i) white (1) precipitate (1) soluble in excess or similar (1) [3]

(ii) white precipitate (1) soluble in excess or similar(1) [2]

(iii) white precipitate (1) [1]

(iv) no reaction/unchanged (1) [1]

(d) fizz/bubbles (1) limewater milky (1) [2]

(e) water (of crystallisation) present (1) [1]

(f) sulphate present (1) chloride/halide absent (1) [2]

(g) B is zinc (1) sulphate (1)

C is (zinc) carbonate (1) [3]

[Sub total = 18]




0620 CHEMISTRY


These mark schemes are published as an aid to teachers and students, to indicate the requirements of the examination. They show the basis on which Examiners were initially instructed to award marks. They do not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the Examination. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session.






1 (a) Boxes completed tubes (1) hydrochloric acid (1) electrodes (1) [3] (b) Electrolysis (1) [1] (c) Litmus paper (1), bleaches/white (1) [2] 2 (a) To extract the colour owtte (1) [1] (b) To remove solid/insoluble impurities (1) [1] (c) Heating/evaporation (1) [1] (d) Diagram showing spots (1) 3 at different levels (1) [2] 3 Maximum temperatures reached 22 34 46 48 44 40 (2) [2] -1 for any incorrect (a) So that the solutions are at same/lab/room temperature (1) [1] (b) 22°C (1) [1] (c) Good insulator owtte (1) [1] (d) Graph all points correct (2) -1 for any incorrect 2 straight lines (1) [3] (e) (i) 50°C (1) [1] (ii) Indication where lines intersect (1) [1] (iii) 24 cm3 or from graph (1) [1] (f) Exothermic (1) [1] 4 Volumes from cylinder diagrams Experiment 2 0 16 31 39 all correct (2) [2] -1 for any incorrect Experiment 3 0 9 17 21 all correct (2) [2]




Experiment 4 0 6 11 14 all correct (2) [2] (a) Graph. All points plotted correctly (3). -1 for each incorrect smooth curves (1), labels (1) [5] (b) (i) Experiment 1 (1) [1] (ii) Most concentrated solution (1), more collisions (1) [2] (c) (i) Two errors (2) e.g. amount of catalyst/timing/volume of solution [2] (ii) Two improvements (2) e.g. measure mass of catalyst/use burette or pipette/data logging [2] (d) Filter (1), same mass of catalyst before and after (1)/repeat experiment and compare

volumes of gas collected [2] 5 (b) (i) white (1), precipitate (1), dissolves/soluble (1) [3] (ii) white (1), precipitate (1), dissolves/soluble (1) [3] (d) reference to water (1) e.g. hydrated salt [1] (e) sulphate (1), not a chloride (1) [2] (f) carbon dioxide (1), from a carbonate (1) [2] 6 Measured volume of oven cleaner (1) Add indicator/named indicator (1) Add named acid (1), from a burette/pipette (1) Until colour change/end point (1), measure/record volume of acid (1) Repeat with other cleaner (1), compare (1) Max 6 [6] Total for paper = 60




0620 CHEMISTRY

0620/01 Paper 1 (Multiple Choice), maximum raw mark 40

Mark schemes must be read in conjunction with the question papers and the report on the examination.

• CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2007 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.




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Question Number

Key Question Number

Key

1 D 21 D

2 D 22 C

3 A 23 A

4 D 24 B

5 B 25 D

6 B 26 B

7 C 27 A

8 A 28 B

9 A 29 B

10 D 30 C

11 B 31 B

12 B 32 D

13 B 33 D

14 D 34 A

15 B 35 B

16 C 36 A

17 C 37 C

18 A 38 A

19 C 39 D

20 C 40 B




0620 CHEMISTRY

0620/02 Paper 2 (Core Theory), maximum raw mark 80

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began.

All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated.






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1 (a) ALLOW: correct names / correct formulae (i) B [1] (ii) E [1] (iii) D [1] (iv) E [1] (v) C [1] (vi) B + C [1] (vii) A + F [1] (b) (i) car exhausts / from vehicles [1] ALLOW: from metal smelting NOT: from factories / from natural causes e.g. volcanoes NOT: from fuels if unqualified (ii) damage to brain / nervous system (in children) [1] ALLOW: mental damage / poisonous / toxic / lung irritant NOT: harmful / lung cancers / poisonous to lungs / makes you ill / respiratory diseases / lung problems etc. (c) forms sulphur dioxide / acid rain [1] ALLOW: sulphur burns to form acid rain REJECT: carbon monoxide / dioxide causes acid rain = 0 REJECT: sulphur causes acid rain = 0 effect of acid rain [1] e.g. chemical erosion / chemical weathering / corrodes metals / damages trees [or plants] / kills trees [or plants] / damages limestone buildings / damages or kills plants [or animals] in lakes NOT: harmful / makes soils acidic / corrodes limestone [or buildings] / pollutant REJECT: global warming / affects ozone layer

[Total: 11]



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2 (a) nitrogen / N2; oxygen / O2 [2] (b) (i) carbon dioxide / CO2 [1] (ii) water / H2O [1] (iii) O2 on left; correct balance [2] (c) (i) (Period) 3 [1] (ii) noble gases / inert gases [1] ALLOW: group 0 / 8 (iii) correct electronic structure of argon 2.8.8 [1] (iv) inert / doesn’t react / prevents (tungsten) filament from burning [1] ALLOW: implication that argon produces light after excitation by electric current (discharge tubes) NOT: argon produces light when it reacts NOT: argon lights up (v) 22 [1] (d) 169 [1] IGNORE: units (e) (i) XeF4O (atoms in any order) [1] (ii) covalent [1] NOT: double and single bonding

[Total: 14]



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3 (a) (i) 2 on both sides (NOTE: only one mark) [1] (ii) comes from water / water won’t run out / water renewable resource [1] NOT: arguments about pollution NOT: easily made / renewed REJECT: found in air and water (iii) exothermic [1] (b) carbon dioxide / CO2; water / H2O [2] (c) 1 mark for each correct fraction; [2] correct use linked to each specific fraction [2] (if fraction incorrect mark cannot be given for use) Examples:

Fraction Use

Refinery gas NOT: methane / natural gas

fuel (alone or qualified) ALLOW: for heating / cooking

Naphtha feedstock for chemicals / making specific chemicals e.g. ethane

Paraffin / kerosene oil stoves / heating / aircraft fuel / feedstock for chemical industry ALLOW: for cooking NOT: fuel alone

Diesel fuel in cars / fuel for diesel engines / central heating fuel NOT: fuel alone

Fuel oil fuel for ships and power stations NOT: fuel alone

Lubricating fraction lubricants / waxes / polishes

Bitumen / residue roads / sealing roofs

(d) (i) breaking down of (larger) hydrocarbon molecules into smaller ones / making alkenes from larger alkanes [1] (idea of large hydrocarbons to smaller ones) ALLOW: breaking down petroleum fractions / hydrocarbons / alkanes NOT: decomposing unless qualified



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(ii) high temperature [1] ALLOW: heat REJECT: heat and burn catalyst OR high pressure [1] ALLOW: aluminium oxide / silicates; IGNORE: incorrect name of catalyst NOT: high pressure (Catalyst + high pressure = 1 mark maximum) (iii) correct structure of ethene [1] All atoms and bonds must be shown

[Total: 13] 4 (a) (i) substance which speeds up (rate of) reaction [1] NOT: slows rate of reaction (ii) transition elements / transition metals [1] NOT: specific metals / named metals (b) (i) axes correctly labelled with time on horizontal axis and use of full grid [1] ALLOW: V for volume and t for time correct plotting of points (-1 per error / omission) [2] Penalise 110 cm3 points only once smooth line going through all points [1] (ii) line steeper at start; [1] ending up at same level [1] NOT: ending up after 50 mins NOT: joining previous line before 50 minutes (iii) all zinc used up / hydrochloric acid is in excess [1] ALLOW: zinc and hydrochloric acid have completely reacted NOT: reaction finished / completed / HCl completely reacted (c) (i) (speed would be) faster / rate increases [1] (comparative needed) NOT: takes less time / reacts more (ii) (speed would be) slower / rate decreases [1] (comparative needed) NOT: takes more time / reacts less (d) (i) zinc chloride [1] (ii) lighted splint / light the gas; [1] pops / explodes etc. [1]

[Total: 14]



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5 (a) electron [1] (b) any two of: conducts electricity / conducts heat / shiny / malleable / ductile / sonorous [2] NOT: high density / high melting point / high boiling point / hard ALLOW: solid if qualified by mercury as exception (c) 4th box down ticked [1] (d) aqueous sodium hydroxide; [1] (light) blue ppt; [1] insoluble in excess [1] OR aqueous ammonia; (light) blue ppt; soluble in excess / forming (dark) blue solution (e) electrical wiring / water pipes / cooking utensils / coinage / any other sensible specific use [1] NOT: for wires / for pipes

[Total: 8]



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6 (a) potassium chloride; [1] bromine [1] (b) iodine lower in group / less reactive than chlorine / iodine less good oxidising agent [1] ALLOW: bond between potassium and chlorine is too strong for iodine to react (c) (i) gas; [1] grey / black; [1] ALLOW: purple black NOT: brown / brown-black / purple (ii) ALLOW range of -200 to -90 (actual = -188); [1] ALLOW range of 1.6 to 4.0 (actual = 3.12) [1] (d) (i) 9 [1] (ii) 7 [1] (e) any suitable use e.g. in swimming pools/ water purification / disinfectant / kills germs / kills bacteria / bleaching agent (for paper) / extraction of titanium / de-tinning scrap tinplate etc. [1] ALLOW: making named chemicals e.g. making hydrochloric acid / making halogenoalkanes / making CFCs / making carbon tetrachloride NOT: sewage treatment / cleaning

[Total: 10]



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7 (a) it is below the electrolyte [1] (b) graphite [1] (c) A [1] (d) aluminium is too reactive / a very reactive metal / above carbon in the reactivity series [1] NOT: because carbon won’t remove the oxygen from the oxide / won’t reduce the oxide / won’t react (e) (i) the aluminium oxide / the electrolyte [1] (ii) CO2 [1] (iii) carbon is released as carbon dioxide / carbon dioxide is a gas [1] NOT: it’s getting oxidised / reaction between carbon and oxygen (f) 530 (kg) [1] (g) molten; ions [2]

[Total: 10]




0620 CHEMISTRY

0620/03 Paper 3 (Extended Theory), maximum raw mark 80








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An incorrectly written symbol, e.g. NA or CL, should be penalised once in the paper. 1 (a) (i) coal or coke or peat [1] NOT wood or charcoal (ii) natural gas or methane or propane or butane or petroleum gases or calor gas or

refinery gas [1] (b) (i) petrol or gasoline paraffin or kerosene diesel aviation fuel or jet fuel fuel oil heavy fuel oil heating oil Any TWO [2] NOT a named alkane e.g. octane (ii) waxes or grease or lubricants or polishes or bitumen (tar, asphalt) or naphtha [2] Any TWO from the primary or secondary distillation of petroleum (iii) (liquid) air or ethanol and water or alkenes (made by cracking) or Noble Gases

[1] [Total: 7] 2 good [1] named example e.g. sodium chloride [1] ACCEPT correct formula silica or silicon(IV) oxide or sand or silicon oxide named polymer only TWO elements [1] electrons [1] and positive ions [1] [2] good [1] [Total: 6] 3 (i) method C [1] sulphuric acid (allow if given in equation) [1] zinc oxide + sulphuric acid = zinc sulphate + water [1] (ii) method A [1] hydrochloric acid [1] KOH + HCl = KCl + H2O [1] (iii) method B [1] potassium iodide or any soluble iodide [1] Pb2+ + 2I- = PbI2 accept a correct equation even if soluble iodide is wrong [2] Not balanced - Pb2+ + I- = PbI2 ONLY [1] [Total: 10]



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4 (a) (i) BaO [1] (ii) B2O3 [1] (b) (i) S2- [1] (ii) Ga3+ [1] (c) NCl3 [1] COND 8e (1bp and 3nbp) around each chlorine [1] 8e (3bp and 1nbp) around nitrogen [1] (d) (i) ignore a correct chemical property in (i) vanadium harder vanadium higher melting point or boiling point vanadium higher density ANY TWO [2] OR corresponding statements for potassium NB has to be comparison (ii) ignore a correct physical property in (ii) potassium more reactive or example of different reactivities- potassium reacts with cold water, vanadium does not. potassium one oxidation state, vanadium more than one vanadium coloured compounds, potassium white or colourless vanadium and its compounds catalysts, not potassium ANY TWO [2] NB has to be comment about both elements (e) (i) fluorine gas [1] astatine solid [1] (ii) both have valency of one both can react with other elements to form halides both are oxidants or any correct Chemistry – they both form acidic hydrides both have diatomic molecules both accept one electron or form ion X- both have seven valency electrons both react with non-metals to form covalent compounds both react with metals to form ionic compounds both form acidic oxides NOT have a valency of 7 ANY TWO [2] [Total: 15]



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5 (a) (i) air would react (with the magnesium or titanium) OR argon would not react (with the metals) [1] NOT argon is inert (ii) any metal higher than magnesium in reactivity series [1] (iii) add water (to dissolve salt) [1] filter or centrifuge [1] (b) (i) electron loss [1] (ii) hydrogen [1] (iii) oxygen [1] chlorine [1] (iv) it cannot lose electrons (because) [1] it receives electrons (from the battery) [1] OR reduction occurs at the cathode [1] oxidation at the anode (not cathode) [1] OR electrons are “pushed” to rig [1] preventing it from being oxidised [1] for comments of the type – rusting needs oxygen, it is formed on titanium not iron ONLY [1] NOT the idea that titanium is more reactive etc (v) SET 1 sacrificial protection is a cell does not need electricity cathodic protection is electrolysis cathodic protection needs electricity SET 2 sacrificial protection needs a more reactive metal (in contact with iron or steel) this metal corrodes instead of steel cathodic protection needs an inert electrode accept unreactive or less reactive metal as

an electrode has to be ONE comment from each set [2] all comments about oxide layers and coating are neutral [Total: 12]



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6 (a) alumina or aluminium oxide [1] sodium aluminate [1] iron(III) oxide [1] filtration or centrifuge NOT conditional [1] (b) from left to right: carbon cathode or carbon negative electrode [1] 900 to 1000oC [1] aluminium [1] cryolite [1] (c) (i) Al3+ + 3e = Al [2] not balanced [1] Al3+(aq) = 0 (ii) oxygen is formed NOT oxide [1] reacts with carbon anode [1] (d) (i) low density or light or resistant to corrosion accept strength/weight ratio or alloys are strong [1] strong on its own is neutral (ii) not attacked or corroded or unreactive oxide layer easily shaped or malleable or ductile any TWO [2] (iii) for strength or so it does not break or does not sag or can have pylons further apart

[1] NOT steel is a better conductor NOT aluminium protects steel from rusting [Total: 16]



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7 (a) butanol [1] no number needed but if one is given it has to be 1 structural formula (all bonds shown) [1] accept –OH NOT –HO ethanoic acid [1] structural formula (all bonds shown) [1] accept –OH NOT –HO no conseq marking if all bonds are not shown ( CH3–CH2–), penalise once (b) (i) must have correct ester linkage [1] COND continuation and a group on either side of the ester group [1] Accept –COO– (ii) accept any sensible suggestion ropes, clothing, bottles, packaging, bags [1] (c) (i) 8 [1] (ii) double bond becomes single and 4 bonds per carbon atom [1] COND a bromine atom on each carbon [1] C2H4Br2 ONLY [1] accept a structural formula with hydrogen atoms (iii) corn oil [1] (d) 100g of fat react with 86.2g of iodine 884g of fat react with 762 g of iodine [1] limit 762 x 2 one mole of fat reacts with 762/254 moles of iodine molecules one mole of fat reacts with 3 moles of iodine molecules [1] number of double bonds in one molecule of fat is 3 [1] limit 6 consequential marking allowed provided the number of double bonds is an integer. [Total: 14]




0620 CHEMISTRY

0620/05 Paper 5 (Practical), maximum raw mark 40








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1 Table of results Experiment 1 initial and final volume boxes correctly completed (1) to 1 dec. place (1) comparable to supervisor ± 5cm3 (1) [3] Experiment 2 initial and final volume boxes correctly completed (1) to 1 dec. place (1) comparable to supervisor ± 5cm3 (1) [3] (a) brown / orange / red / amber / precipitate (1) [1] (b) becomes redder / yellow / orange / paler (1) [1] (c) (i) yellow (1) to blue / black (1) [2] NOT: green (ii) as an indicator owtte [1] NOT: test for iodine (d) (i) Experiment 1 (1) [1] (ii) more in Experiment 1 / greater volume (1) [1] (iii) solution A more concentrated / stronger than B (1) X2 (1) [2] (e) half X value from table (1) cm3 / cc / ml (1) [2] (f) change e.g. repeat titrations (1) explanation e.g. average reading more accurate (1) [2]

[Total: 19]



© UCLES 2007

2 (a) reference to green (1) – refer to supervisor [1] (b) paper turns blue / green / reference to smell (1) pH 8-11 (1) [2] solid is yellow / brown / grey / charred or reference to sublimate (1) [1] (c) fizz / bubbles / effervescence (1) [1] (d) yellow (1) precipitate (1) fizz / bubbles (1) [3] (e) (i) white (1) precipitate (1) [2] (ii) green (1) precipitate (1) [2] (iii) green precipitate (1) [1] paper turns blue / green / reference to smell (1) pH 8-11 (1) [2] (f) lead (1) carbonate (1) [2] (g) iron (1) (II) (1) ammonium (1) sulphate (1) [4]

[Total: 21]




0620 CHEMISTRY

0620/06 Paper 6 (Alternative to Practical), maximum raw mark 60








© UCLES 2007

1 (a) A thermometer (1) B beaker (1) C tripod (1) [3] (b) to cool / condense the vapour (1) [1] (c) measure the boiling point (1) [1] [Total: 5] 2 (a) Correct indication of electrodes (1) [1] (b) bubbles / fizz / effervescence (1) / green gas / level of liquid falls (1) bulb lights up (1) max 2 [2] (c) (i) chlorine / Cl2 (1) [1] (ii) litmus paper / indicator (1) bleaches (1) [2] [Total: 6] 3 (a) does not dissolve in solvent / interfere with results owtte (1) [1] (b) 1 and 3 (1) [1] (c) sample 4 (1) two spots present (1) [2] (d) to show position of the acids / spots (1) [1] [Total: 5]



© UCLES 2007

4 Table of results Experiment 1 final reading box correctly completed, 39.2 (1) Experiment 2 final reading box correctly completed (1) differences completed correctly, 39.2 (1) and 20.6 (1) [4] (a) as an indicator owtte [1] (b) (i) Experiment 1 (1) [1] (ii) more in Experiment 1 / greater volume (1) [1] (iii) solution A more concentrated / stronger than B (1) approx ×2 (1) [2] (c) 10.3 (1) cm

3 / ml / cc (1) [2]

(d) change e.g. repeat titrations (1) explanation e.g. average reading more accurate (1) [2] [Total: 13] 5 (c) bubbles / fizz (1) limewater (1) milky (1) [3] (d) yellow (1) precipitate (1) [2] (f) carbon dioxide (1) [1] (g) ammonia (1) [1] (h) iron (1) (II) (1) ammonium (1) sulphate (1) [4] [Total: 11]



© UCLES 2007

6 table correctly completed

catalyst W catalyst X

0 0

16 29

32 34

36 36

37 37

37 37

all correct (3) -1 each incorrect

[3] (b) graph choice of suitable scale for y-axis (1) all points correctly plotted (3) smooth curves (1) labelled (1) [6] (c) solid X (1) faster reaction / more gas given off at 20/40 s (1) [2] (d) same volume of hydrogen peroxide used in both experiments (1) [1]

(e) line sketched on grid with steeper slope than for catalyst X at 25°C (1) levelling out at same level (1) [2] [Total: 14] 7 (a) initial temperature of cold water or cement (1) add cement (1) using thermometer / in beaker etc. (1) measure temperature (1) temperature rise (2) max 4 [4] NB no water = 0 no cement = 0 use of heat = 0 wrong chemicals = 0 would not work = 0 (b) sodium hydroxide (1) white precipitate (1) [2] or flame test (1) red (1) [Total: 6]




0620 CHEMISTRY







© UCLES 2008

Question Number

Key Question Number

Key

1 C 21 D

2 A 22 D

3 C 23 A

4 C 24 D

5 C 25 B

6 D 26 D

7 A 27 B

8 C 28 A

9 A 29 B

10 B 30 D

11 D 31 C

12 A 32 D

13 D 33 C

14 B 34 A

15 C 35 D

16 B 36 A

17 B 37 B

18 C 38 C

19 D 39 B

20 C 40 B




0620 CHEMISTRY









© UCLES 2008

1 (a) (i) B/calcium carbonate/CaCO3 [1]

(ii) E [1]

(iii) C/carbon dioxide/CO2 [1]

(iv) D/ethane [1] (b) bromine water/bromine [1] decolourises/turns colourless [1] NOT: turns clear ALLOW: (acidified) potassium manganate(VII); turns colourless (2 marks) IGNORE: original colour of bromine/potassium manganate(VII) (c) calcium carbonate [1] NOT: CaCO3 (d) lubricant/2nd box down ticked [1] IF: more than one box ticked = 0 (e) substance containing more than one type of atom different atoms ALLOW: more than one type of element/two elements bonded/joined/(chemically) combined/combination [1] Both parts needed. IF: word mixture appears = 0 (f) covalent [1] NOT: single bonding [Total: 10] 2 (a) calcium carbonate [1] (b) any 4 from: • statue becomes (chemically) eroded; ALLOW: statue becomes corroded/amount of limestone reduced NOT: destroys limestone/limestone melting/damages the statue • iron pins corroded/eroded/eaten away OWTTE • acid rain; • caused by burning fossil fuels; • sulphur dioxide formed/from sulphur in fossil fuels; ALLOW: nitrogen dioxide formed/from car exhausts • sulphur dioxide dissolves to form acid; ALLOW: nitrogen dioxide dissolves to form acid • sulphuric acid in air ALLOW: nitric acid in air • acid reacts with limestone/carbonate/statue/iron/pins NOT: (unqualified) acid reacts [4]



© UCLES 2008

(c) iron/pin(s) corrode/rust/eaten away/erode/oxidises [1] ALLOW: iron pins dissolve away ALLOW: iron/pins react with (acid) in air NOT: iron pins have reacted/weak and break NOT: it/the arm has rusted

(d) (i) atoms (of same element) with different number of neutrons/atoms with different numbers of nucleons but same number of protons/ same elements [1]

ALLOW: atoms with same atomic number but different mass number (ii) –/negative [1] 0/no charge [1] +/positive [1] IGNORE: numbers in front of – or + (iii) 56 [1] ALLOW: 30 + 26 (e) any suitable use e.g. measuring thickness of paper/detecting leaks in pipes (ALLOW: checking leakage for suitable substances e.g. water/oil) /sterilization of surfaces/making electricity/power stations/ [1] NOT: medical uses (f) iron + nitric acid → iron nitrate + hydrogen [1] IGNORE: oxidation numbers unless incorrect/dilute (nitric acid) NOT: heat on either side of equation/equation without arrow ALLOW: = for arrow [Total: 13] 3 (a) Cl

–/chloride [1] (b) sulphate [1] IGNORE: oxidation numbers (c) potassium + sodium (both needed for the mark) [1] ALLOW: K+ and Na+/K and Na (d) sodium chloride [1] ALLOW: NaCl ALLOW: salt (e) any two of: calcium/magnesium/potassium/sodium [2]



© UCLES 2008

(f) (i) 3 (rd period) [1] (ii) single bonding pair [1] 6 non-bonding electrons in each atom [1] IGNORE: incorrect inner electrons (g) any 2 of: [2] • distillation removes dissolved ions/ salts; ALLOW: distillation removes only the water/extracts water/solvent IGNORE: reference to impurities without qualification • filtration doesn’t remove dissolved ions/salts; ALLOW: filtration can’t remove very small particles OWTTE ALLOW: filtration only removes large particles IGNORE: filtration removes solids IGNORE: reference to impurities • filtration does not remove bacteria/germs; • distillation removes/kills bacteria/germs IGNORE: cost/speed arguments [Total: 11] 4 (a) any suitable e.g. as a coolant/for specific named reactions e.g. making ethanol from

ethene/making sulphuric acid [1] ALLOW: as a solvent ALLOW: to make hydroelectricity/electricity NOT: (unspecified) making chemicals NOT: to drink/wash, etc. (b) any two of: [2] • sand has very fine/small spaces (between the grains) (idea of small spaces) • water/small molecules/small particles can pass through; (idea of small molecules going through) • water molecules are small/water is a liquid; (water molecules small/liquid) • (large) particles cannot pass through spaces/are trapped by sand/blocks particles/ (idea of particles not getting though/trapping by sand) NOT: by filtering NOT: filter takes out the smaller molecules in water IGNORE: references to absorbing/impurities (c) add sodium hydroxide; [1] white ppt/milky ppt/white solid (both white and ppt/solid needed); [1] soluble in excess/gives colourless solution in excess [1] OR add (aqueous) ammonia; white ppt; insoluble in excess/does not redissolve (d) to kill bacteria/germs [1] ALLOW: antibacterial/kills harmful organisms NOT: dissolves bacteria ALLOW: to stop bacteria growing



© UCLES 2008

(e) (i) chlorine + potassium bromide → potassium chloride + bromine [2] (–1 for each error or omission including no arrows/heat on left) (ii) it/iodine is less reactive than bromine/iodine lower in the reactivity series than bromine

ORA [1] NOT: iodine lower in the reactivity series than bromide

NOT: iodine lower in the reactivity series than potassium bromide/iodine can’t displace bromine

NOT: its not reactive enough/lower in the Periodic Table (f) (i) exothermic [1] (ii) ionic [1] (iii) sodium (atom) loses an electron [1] chlorine (atom) gains an electron [1] [sodium (atom) gives an electron to chlorine = 2] IGNORE: incorrect number of electrons/ reference to charges NOTE: any reference to sharing electrons = 0] [Total: 14] 5 (a) hydrogen/H2 [1] NOT: H (b) (i) to ensure all the (sulphuric) acid reacted [1] NOT: to ensure it reacted (ii) filtration/filter ALLOW: decanting/pouring off the solution [1] NOT: distillation/evaporation of sulphuric acid (c) evaporate water/evaporation/leave in a warm place; [1] ALLOW: heat/boil then allow solution to cool/heat then evaporate NOT: not heat/boil (to get the crystals) NOT: crystallisation/allow to crystallise; dry crystal on filter paper [1] ALLOW: filter off crystals and allow to dry (d) (i) sulphuric acid + magnesium carbonate/hydroxide/oxide or magnesium + a less reactive metal sulphate [1] NOT: magnesium + sulphuric acid (since in question) (ii) sulphuric acid + magnesium carbonate → magnesium chloride + water + carbon dioxide/ sulphuric acid + magnesium hydroxide → magnesium chloride + water/ sulphuric acid + magnesium oxide → magnesium chloride + water or e.g. magnesium + copper sulphate → magnesium sulphate + copper [1] ALLOW: correct answer(s) in either parts (i) or (ii) ALLOW: correct symbols equations



© UCLES 2008

(iii) contaminants might harm health/may make you ill/cause side effects [1] ALLOW: medicine would not work as well/might cause health problem IGNORE: contain contaminants/poisonous/kills you IGNORE: medicine would not work NOT: decrease the effect (unless specified of what i.e. of the medicine) (e) 6 (g) [1] IF: unit incorrect = 0 (f) 97.5 (%) [1] [Total: 10] 6 (a) (i) (group of) molecules/compounds with similar boiling points/group of molecules/

compounds which distil at same place in the fractionating column [1] (ii) fuel gas [1] ALLOW: methane (iii) Any two of: • temperature gradient in column/column hotter at bottom/column colder at top; • different fractions have different boiling points ALLOW: separated according to their boiling points/each fraction forms at a different

temperature • molecules condense/turn from gas to liquid at different heights in the column; • molecules condense/turn to liquid when temperature drops below their boiling point; ALLOW: molecules condense at their boiling point; • smaller molecules move further up the column ORA larger molecules/molecules with higher boiling point condense lower in the column

or smaller molecules/molecules with lower boiling point condense higher in column = 2 [2]

(iv) oil stoves/aircraft (fuel)/(fuel for) lamps [1] NOT: fuels for power stations/for burning/starting fires road (surfacing)/(tar for) roofing [1] ALLOW: paint NOT: tar without qualification

(b) (i) breaking down of larger molecules/hydrocarbons/converting large molecules into small molecules/large chains to small chains [1]

IGNORE: conditions NOT: implication of reacting with something else NOT: breaking larger substances to smaller NOT: breaking high fractions to low fractions (ii) C12H26 [1] ALLOW: other correctly balanced combinations within reason e.g. C10H22 + 2C2H4 or with

3 species



© UCLES 2008

(c) (i) speeds up rate of reaction [1] ALLOW: alters/changes rate of reaction (ii) reversible (reaction)/equilibrium (reaction)/reaction can go both ways [1] IGNORE: exothermic/endothermic (iii) fermentation [1] (iv) turns red/pink; [1] bubbles/ effervescence/fizzes [1] IGNORE: temperature changes/ppt/neutralises NOT: gas/carbon dioxide formed [Total: 13] 7 (a) Any 2 of: • crystals dissolve • water molecules colliding with crystal • diffusion • movement of ions NOT: copper particles/copper atoms/copper molecules NOT: particles slide over each other • movement of water molecules/water particles • movement is random [movement of (unspecified) particles = 1 maximum] NOT: movement of water/copper sulphate/crystals NOT: particles spread out IGNORE: movement from high to low concentration [2] (b) arrangement: regular [1] ALLOW: particles close together/linear/in lines/lattice/closely packed motion: none/vibrating [1] NOT: does not move a lot (c) suitable container with filter paper dipping into labelled solvent; [1] spot above solvent level [1] IF: metal ion where the solvent should be = 0 marks (d) (i) cathode [1] (ii) pure foil: gets further copper deposit/increases in thickness/gets less shiny [1] ALLOW: gets heavier/mass increases ALLOW: Cu2+ + 2e– → Cu (ignore wrong balance) impure foil: copper removed/decreases in thickness/appears cleaner [1] ALLOW: gets lighter/decreases in mass/dissolves/is corroded ALLOW: Cu → Cu2+ + 2e– NOT: wears away NOT: disappears [Total: 9]

Location Entry Codes

As part of CIE’s continual commitment to maintaining best practice in assessment, CIE has begun to use different variants of some question papers for our most popular assessments with extremely large and widespread candidature, The question papers are closely related and the relationships between them have been thoroughly established using our assessment expertise. All versions of the paper give assessment of equal standard. The content assessed by the examination papers and the type of questions are unchanged. This change means that for this component there are now two variant Question Papers, Mark Schemes and Principal Examiner’s Reports where previously there was only one. For any individual country, it is intended that only one variant is used. This document contains both variants which will give all Centres access to even more past examination material than is usually the case. The diagram shows the relationship between the Question Papers, Mark Schemes and Principal Examiner’s Reports.

Question Paper Mark Scheme Principal Examiner’s Report

Introduction Introduction Introduction

First variant Question Paper First variant Mark Scheme First variant Principal Examiner’s Report

Second variant Question Paper Second variant Mark Scheme Second variant Principal Examiner’s Report

Who can I contact for further information on these changes? Please direct any questions about this to CIE’s Customer Services team at: [email protected]





0620 CHEMISTRY






maigna

First variant



© UCLES 2008

An incorrectly written symbol, e.g. NA or CL, should be penalised once in a question. 1 (a) bromine [1] (b) germanium [1] (c) potassium or calcium [1] (d) krypton [1] (e) iron or cobalt [1] (f) bromine [1] (g) vanadium [1] ACCEPT name or symbol [Total: 7] 2 (a)

electron e- or e 1/1840 or 1/2000 or 0 1/1837 or negligible

-1

proton p or p+ or H+ 1 +1

neutron n 1 0 or neutral

each correct row (1) [3]

(b) (i) equal numbers of protons and electrons of positive and negative charges or charges cancel/balance [1]

or net charge = 0 [1] (ii) lose electron(s) [1] more protons than electrons [1] NOT more + than – (iii) different numbers of neutrons [1] same number of protons or same number of electrons [1] for just giving- they are isotopes [1] ONLY (iv) an element is known for each proton number [1] accept any sensible idea, for example no gaps between z = 1 and z = 103 [Total: 10]

maigna

First variant



© UCLES 2008

3 (a) impure copper [1] (pure) copper [1] ACCEPT any (soluble) copper salt or Cu2+ [1] if both name and formulae given, both have to be correct (b) Cu - 2e � Cu2+ or Cu � Cu2+ + 2e [2] for having Cu � Cu2+ [1] ONLY (c) (i) good conductor [1] malleable or ductile [1] good conductor of heat high melting point (and high boiling point) unreactive or resists corrosion appearance any TWO [2] do not accept malleable or ductile if either is given for wiring (ii) alloys or named alloy or pipes or ornaments or jewellery or integrated circuit boards or

electroplating or roofs, etc. [1] [Total: 10] 4 (a) (i) magnesium + sulphuric acid = magnesium sulphate + hydrogen [1] ACCEPT hydrogen sulphate (ii) Li2O + H2SO4 � Li2SO4 + H2O [2] formulae correct but not balanced [1] (iii) CuO + H2SO4 � CuSO4 + H2O [2] OR CuO + 2HCl � CuCl2 + H2O OR CuO + 2HNO3 � Cu(NO3)2 +H2O formulae correct but not balanced [1] (iv) sodium carbonate + sulphuric acid � sodium sulphate + carbon dioxide + water [1] (b) it accepts a proton [2] it accepts a hydrogen ion [1] ONLY (c) sulphuric acid is completely ionised [1] or few molecules and many ions ethanoic acid is partially ionised [1] or many molecules and few ions [Total: 10]

maigna

First variant



© UCLES 2008

5 (a) (i) (concentration) of reactants/CO and Cl2 increases [1] (concentration) of product decreases/COCl2) [1] (ii) (decrease in pressure favours side) with more molecules or moles or side with bigger volume (of gas) [2] NB [2] or [0] (b) forward reaction is exothermic [1] COND because it is favoured by low temperatures or cool [1] ACCEPT argument re back reaction (c) hydrogen chloride or hydrochloric acid [1] carbon dioxide or carbonic acid or hydrogen carbonate [1] (d) 8e around both chlorine atoms [1] 4e between carbon and oxygen atoms [1] 8e around carbon atom [1] 8e around oxygen [1] if a bond contains a line with no electrons, no marks for atoms joined by that line ignore keying

[Total: 12]

6 (a) (i) (fine powder) large surface area [1] high/faster/collision rate/more collisions/fast collisions (between solid and oxygen in air) [1] (ii) carbohydrate + oxygen � carbon dioxide + water [1] ACCEPT flour (b) rate depends on light more light more silver or blacker thicker card less light [3] (c) (i) biological catalyst [1] accept protein catalyst (ii) production of energy (from food) [1] by living “things” or by cells, etc. [1] (iii) “kill” yeast or denature enzymes (due to increase in temperature) [1] (iv) all glucose used up [1] yeast “killed” or denatured or damaged by ethanol/alcohol [1] (v) filter or centrifuge [1] fractional distillation [1]

[Total: 14]

maigna

First variant



© UCLES 2008

7 (a) repeat experiment without indicator or use carbon to remove indicator [1] (partially) evaporate or boil or heat [1] allow to cool or crystallise or crystals [1] dry crystals [1] MUST be in correct order NB evaporate to dryness, marks one and two ONLY (b) number of moles of NaOH used = 0.025 x 2.24 = 0.056 [1] maximum number of moles of Na2SO4.10H2O that could be formed = 0.028 [1] mass of one mole of Na2SO4.10H2O = 322g maximum yield of sodium sulphate – 10 - water = 9.02g [1] percentage yield = 42.8% [1] mark ecf but NOT to simple integers if ecf marking, mark to at least one place of decimals if percentage > 100% then 3/4 maximum [Total: 8] 8 (a) burning wood produces carbon dioxide [1] less photosynthesis or trees take up carbon dioxide [1] (b) (i) fats or lipids [1] (ii) -O- linkage, no other atoms in linkage [1] COND same monomer [1] COND continuation bonds at each end -A- [1] (iii) same linkage or amide linkage or peptide or –CONH- [1] differences synthetic polyamide usually two monomers protein many monomers protein monomers are amino acids or proteins hydrolyse to amino acids or a protein

monomer has one – NH2 and one –COOH group synthetic polyamide each monomer has 2 –NH2 or 2COOH groups or monomers are

dioic acid and diamine accept diagrams or comments that are equivalent to the above ANY TWO [2] [Total: 9] [Total for paper: 80]

maigna

First variant




0620 CHEMISTRY






maigna

Second variant



© UCLES 2008

An incorrectly written symbol, e.g. NA or CL, should be penalised once in a question. 1 (a) bromine [1] (b) selenium [1] (c) potassium or calcium [1] (d) krypton [1] (e) iron or cobalt [1] (f) potassium or copper [1] (g) iron [1] ACCEPT name or symbol [Total: 7] 2 (a)

electron e-

1/1840 or 1/2000 or 1/1837 or negligible

-1

proton p 1 +1

neutron n 1 0

each correct row (1) [3] equal numbers of protons and electrons of positive and negative charges or charges

cancel/balance [1] or net charge = 0 [1] (ii) gain electron(s) [1] more electrons than protons [1] NOT more – than + (iii) different number of neutrons [1] same number of protons or electrons [1] (iv) an element is known for each proton number [1] accept any sensible idea, for example – no gaps between z = 1 and z = 103 [Total: 10]

maigna

Second variant



© UCLES 2008

3 (a) impure copper [1] (pure) copper [1] ACCEPT any (soluble) copper salt or Cu2+ [1] if both name and formulae given, both have to be correct (b) Cu - 2e � Cu2+ or Cu � Cu2+ + 2e [2] for having Cu � Cu2+ [1] ONLY (c) (i) good conductor [1] malleable or ductile [1] good conductor of heat high melting point (and high boiling point) unreactive or resists corrosion appearance [2] do not accept malleable or ductile if either is given for wiring (ii) alloys or named alloy or pipes or ornaments or jewellery or integrated circuit boards or

electroplating or roofs, etc. [1] [Total: 10] 4 (a) (i) magnesium + sulphuric acid � magnesium sulphate + hydrogen [1] accept hydrogen sulphate (ii) Li2O + H2SO4 � Li2SO4 + 2H2O [2] all formulae correct, not balanced [1] (iii) CuCO3 + H2SO4 � CuSO4 + H2O + CO2 [2] OR CuCO3 + 2HCl � CuCl2 + H2O + CO2 OR CuCO3 + 2HNO3 � Cu(NO3)2 + H2O + CO2 all formulae correct, not balanced [1] (iv) sodium carbonate + sulphuric acid � sodium sulphate + carbon dioxide + water [1] (b) it accepts a proton [2] it accepts a hydrogen ion [1] ONLY (c) electrical conductivity [1] sulphuric acid is a better conductor or ethanoic acid is a poorer conductor [1] OR rate of reaction a suitable metal or metal carbonate must be named [1] sulphuric acid reacts faster or ethanoic acid reacts slower [1] NOTE [1] for method explicitly stated or implied for valid comparison [1] sulphuric acid is a better conductor [2] sulphuric acid is a good conductor [1] Accept a correct test for a sulphate with a soluble barium salt [Total: 10]

maigna

Second variant



© UCLES 2008

5 (a) (i) (concentration) of reactants/CO and Cl2 decreases [1] (concentration) of product/COCl2 increases [1] (ii) (an increase in pressure favours the) side with fewer molecules or moles, side with

smaller volume (of gas) [2] NB [2] or [0] (b) forward reaction is exothermic [1] COND because it is favoured by low temperatures or cool [1] ACCEPT argument re back reaction (c) hydrogen chloride or hydrochloric acid [1] carbon dioxide or carbonic acid or hydrogen carbonate [1] (d) 8e around both chlorine atoms [1] 4e between the carbon atom and the oxygen atom [1] 8e around carbon [1] 8e around oxygen [1] if a bond contains a line with no electrons, no marks for atoms joined by that line ignore keying [Total: 12] 6 (a) (i) (fine powder) large surface area [1] high/faster/collision rate/more collisions/fast collisions (between solid and oxygen in air) [1] (ii) carbohydrate + oxygen � carbon dioxide + water [1] ACCEPT flour (b) rate depends on light more light more silver or blacker thicker card less light [3] (c) (i) biological catalyst [1] accept protein catalyst (ii) production of energy (from food) [1] by living “things” or by cells, etc. [1] (iii) “kill” yeast or denature or damage the enzymes (due to increase in temperature) [1] (iv) all glucose used up [1] yeast “killed/denature/damaged by ethanol/alcohol [1] (v) filter or centrifuge [1] fractional distillation [1] [Total: 14]

maigna

Second variant



© UCLES 2008

7 (a) repeat experiment without indicator or use carbon to remove indicator [1] (partially) evaporate or heat or boil [1] allow to cool or crystallise or crystals [1] dry crystals [1] NOTE evaporate to dryness, marks one and two ONLY must be in correct order (b) number of moles of NaOH used = 0.025 x 2.64 = 0.066 [1] maximum number of moles of Na2SO4.10H2O that could be formed = 0.033 [1] mass of one mole of Na2SO4.10H2O = 322g maximum yield of sodium sulphate - 10 - water = 10.63g [1] percentage yield = 37.2% [1] mark ecf but NOT to simple integers if ecf marking, mark to at least one place of decimals if percentage > 100% then 3/4 maximum [Total: 8] 8 (a) burning wood produces carbon dioxide [1] less photosynthesis or trees take up carbon dioxide [1] (b) (i) fats or lipids [1] (ii) -O- linkage, no other atoms in linkage [1] COND same monomer [1] COND continuation bonds at each end -A- [1] (iii) same linkage or amide linkage or peptide or –CONH- [1] differences synthetic polyamide usually two monomers protein many monomers protein monomers are amino acids or proteins hydrolyse to amino acids or a protein monomer has one –NH2 and one –COOH group. synthetic polyamide each monomer has 2 –NH2 or 2COOH groups. accept diagrams or comments that are equivalent to the above ANY TWO [2] [Total: 9] [Total for paper: 80]

maigna

Second variant




0620 CHEMISTRY

0620/05 Paper 5 (Practical Test), maximum raw mark 40








© UCLES 2008

1 Experiment 1(a) green precipitate (1) [1] Experiment 2(d) brown/orange/rust precipitate (1) [1] Table of results Experiment 1 initial and final volume boxes correctly completed (1) Experiment 2 initial and final volume boxes correctly completed (2) differences completed correctly (1) comparable to Supervisor’s results ± 5 cm3 (2) [6] (e) (pale) green (1) [1] (f) (turns) yellow (1) [1] (g) (i) Experiment 1 (1) ecf [1] (ii) more in Experiment 1/greater volume (1) [1] (iii) solution A more concentrated/stronger than B (1) ×2 (1) [2] (h) twice the volume value for Experiment 2 (1) cm3/ml (1) [2]

(i) change e.g. repeat titrations (1) or use a burette/pipette explanation e.g. average reading more accurate (1) instead of m/cylinder [2] (j) (i) iron(II) present (1) [1] (ii) iron(III) (1) [1] [Total: 20]



© UCLES 2008

2 Tests on solid T (a) white (1) see Supervisor’s results [1] (b) condensation (1) solid goes black/chars (1) gas ignites/catches fire or flame (1) [max 2] (c) (i) orange/yellow (1) pH6/5 (1) see Supervisor’s results [2] (ii) white (1) precipitate (1) [2] (iii) reddish (1) brown on heating (1) [2] Tests on solid V (d) green (1) [1] (e) solid changes colour to copper/brown (1) [1] (f) smells acidic/vinegar or similar (1) [1] (i) green (1) pH 7/6 (1) see Supervisor’s results [2] (ii) blue (1) precipitate (1) [2] (iii) green (1) [1] (g) calcium present (1) [1] (h) copper present (1) ethanoic acid/organic salt (1) [2] [Total: 20] [Total for paper: 40]




0620 CHEMISTRY









© UCLES 2008

1 (a) boxes correctly completed measuring cylinder (1) spatula (1) tripod (1) [3] (b) more than enough to react owtte (1) [1] (c) diagram showing filter paper in a funnel (1) either labelled (1) [2] [Total: 6] 2 (a) (i) electrodes labelled correctly (1) [1] (ii) carbon/graphite or platinum (1) [1] (b) bulb lights/brownish/red/orange gas/liquid/bubbles/silver beads formed/melts in tube [max 2] (c) any correct protective clothing e.g. gloves/lab coat (1) fume cupboard/well ventilated room (1) [2] [Total: 6] 3 (a) boxes completed correctly to show position of hydrochloric acid (1) and sodium sulphite (1) [2] (b) arrow underneath flask (1) [1] (c) mistakes passed through water (1) collected by upward delivery (1) [2] [Total: 5] 4 Table of results Experiment 1 initial and final volume boxes correctly completed (1), 0.0 and 26.0 Experiment 2 initial and final volume boxes correctly completed (2), 16.0 and 29.0 differences completed correctly (1), 26.0 and 13.0 [4]



© UCLES 2008

(e) (i) Experiment 1 (1) [1] (ii) more in Experiment 1/greater volume (1) ×2 (1) [2] (iii) solution A more concentrated/stronger than B (1) X2 (1) [2] (f) twice the volume value for Experiment 2/26 (1) cm3 (1) [2] (g) change e.g. repeat titrations (1) or use a burette/pipette

explanation e.g. average reading more accurate (1) instead of m/cylinder [2] (h) (i) iron(II) ions present (1) [1] (ii) iron(III) ions (1) [1]

[Total: 15]

5 Tests on solid T (b) (ii) white (1) precipitate (1) insoluble in excess (1) [2] (iii) no/slight (1) precipitate (1) max 4 for (ii) and (iii) [2] no reaction (1) only (e) weak (1) acids (1) [2] (f) copper present(1) ethanoic acid/organic salt (1) [2]

[Total: 8]

6 (a) Table of results

volumes correctly completed (4), -1 for each incorrect

0, 18, 34, 42, 59, 63, 63 [4] (a) points plotted correctly (3), -1 for each incorrect smooth line curve (1) [4] (c) reaction finished/all acid used up (1) [1] (d) point at 3 minutes/at 42 cm3 (1) does not fit curve owtte (1) [2] (e) sketch line below plotted curve (1) levels off around 30 cm3 (1) [2]

[Total: 13]



© UCLES 2008

7 (a) test red litmus (1) or other named indicator result blue (1) [2] (b) fractional (1) distillation (1) fractionation (1) [2] (c) blue cobalt chloride paper (1) turns pink (1) OR anhydrous/white copper sulphate (1) turns blue (1) [2] (d) catches fire owtte (1) [1] [Total: 7] [Total for paper: 60]




for the guidance of teachers

0620 CHEMISTRY




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First Variant Mark Scheme

Mark Scheme: Teachers’ version Syllabus Paper


© UCLES 2009

Question Number

Key Question Number

Key

1 C 21 B

2 B 22 A

3 D 23 A

4 B 24 B

5 D 25 B

6 A 26 A

7 C 27 D

8 D 28 D

9 A 29 C

10 C 30 B

11 D 31 C

12 C 32 D

13 D 33 D

14 B 34 C

15 D 35 D

16 B 36 A

17 B 37 C

18 B 38 A

19 C 39 B

20 C 40 C

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0620 CHEMISTRY




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Second Variant Mark Scheme



© UCLES 2009

Question Number

Key Question Number

Key

1 C 21 A

2 D 22 B

3 B 23 C

4 C 24 B

5 B 25 A

6 D 26 D

7 D 27 B

8 A 28 D

9 A 29 B

10 C 30 C

11 D 31 C

12 B 32 D

13 C 33 C

14 D 34 D

15 B 35 D

16 D 36 C

17 B 37 A

18 C 38 B

19 B 39 C

20 A 40 A

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0620 CHEMISTRY


This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers.






© UCLES 2009

1 (a) (i) iron(III) oxide / iron oxide / Fe2O3; [1] ALLOW: iron (ii) lead(II) bromide / lead bromide / PbBr2; [1] NOT: lead (iii) calcium carbonate / CaCO3; [1] NOT: carbonate (iv) sodium hydroxide / NaOH; [1] ALLOW: hydroxide / OH– NOT: sodium (v) methane; [1] (b) (i) oxygen is removed (from the iron oxide); [1] ALLOW: carbon takes the oxygen from the iron oxide ALLOW: oxygen goes to the carbon / the oxygen combines with the carbon ALLOW: oxidation number of iron decreases / electrons added to iron NOT: the iron oxide loses electrons (ii) haematite; limestone; blast; slag; [4] [Total: 10] 2 (a) calcium, magnesium, iron, copper; [1] (b) bubbles produced steadily / moderately / slowly / bubbles produced faster than iron and slower than magnesium / fewer bubbles than magnesium and more than iron; [1] ALLOW: many bubbles produced but less than magnesium NOT: bubbles produced rapidly / less rapidly NOT: less bubbles than magnesium / more bubbles than iron NOT: reaction / it’s faster than iron and slower than magnesium (c) (i) magnesium floats on top of the magnesium chloride ORA / magnesium is above the magnesium chloride ORA; [1] ALLOW: magnesium is on top of the magnesium chloride ORA (ii) (magnesium) too reactive / above carbon in reactivity series / more reactive than

carbon; [1] ALLOW: magnesium is a reactive metal / magnesium is reactive ALLOW: too high a temperature needed for the extraction NOT: magnesium oxide / magnesium will not react with carbon



© UCLES 2009

(iii) to prevent magnesium reacting with the air / oxygen / nitrogen; [1] ALLOW: to stop magnesium oxidising NOT: because it is reactive NOT: to stop it reacting NOT: because inert gases are unreactive (iv) nitrogen / helium / neon / argon / krypton / xenon / radon; [1] (d) (i) structure of ethene showing all atoms and all bonds; [1] ALLOW: correct electronic structure (ii) two of: [2] (1 mark each)

• carbon monoxide + poisonous / toxic; ALLOW: carbon monoxide combines with haemoglobin / red blood cells ALLOW: carbon monoxide suffocates NOT: carbon monoxide harmful / dangerous

• hydrogen + flammable / explosive; NOT: hydrogen dangerous

• hydrogen sulfide + poisonous / toxic; ALLOW: harmful NOT: dangerous / affects breathing

• ethene + flammable;

• methane + flammable; ALLOW: explosive

(e) (i) carbon monoxide + water / steam → carbon dioxide + hydrogen; [1] ALLOW: arrow for equilibrium sign NOT: carbon oxide instead of carbon monoxide NOT: mixture of words and symbols (ii) equilibrium / reversible reaction / the reaction can go both ways / the reaction can

go backwards or forwards; [1] ALLOW: the reaction can also go backwards NOT: the reaction goes backwards (iii) add sodium hydroxide (solution) / (aqueous) ammonia; [1] (red-)brown / rusty red precipitate (both points); [1] ALLOW: solid for precipitate ALLOW: yellow-brown precipitate / orange precipitate IGNORE: references to excess ammonia / sodium hydroxide NOT: red precipitate [Total: 13]



© UCLES 2009

3 (a) (fractional) distillation; [1] ALLOW: fractionation (b) Two of: [2]

• fuel gas / refinery gas;

• naphtha;

• light gas oil / heavy gas oil / fuel oil;

• lubricating oil / lubricating fraction; (NOT: lubricant)

• bitumen; (ALLOW: residue) IGNORE: kerosene / paraffin / gasoline / petrol / diesel IGNORE: methane / named chemical compounds IGNORE: gas alone (c) oil stoves / aircraft fuel / for jet engines / for car engines; [1] ALLOW: for making more petrol ALLOW: for cooking / for heating / for lighting / for fuel (d) A and D; (both needed) [1] (e) ethane; unreactive; oxygen; water; [4] (f) saturated: has only single bonds / contains the maximum amount of hydrogen atoms

(that can be combined with carbon atoms); [1] ALLOW: does not have double bonds ALLOW: consists of single bonds NOT: has single bonds hydrocarbon: (compound / substance) containing hydrogen and carbon only / it has

carbon and hydrogen only; [1] REJECT: it has carbon and hydrogen molecules only / ideas of mixtures of carbon and

hydrogen [Total: 11]



© UCLES 2009

4 (a) ammonia / NH3; [1] (b) goes blue; [1] ALLOW: goes purply-blue NOT: goes blue then bleaches NOT: goes purple (c) ammonium chloride; carbon dioxide; water; [3] NOT: formulae NOT: ammonia chloride (d) (i) to replace nitrogen lost from soil; [1] ALLOW: to make (crop) plants grow better ALLOW: to make plants grow more / faster ALLOW: to improve crop yield IGNORE: to replace minerals lost from the soil / to replace nutrients (ii) more nitrogen / greater percentage of nitrogen; [1] NOT: more nitrate (iii) 80; [1] (e) oxygen / O2; [1] NOT: O (f) acid rain / effect of acid rain e.g. trees or plants die / pond animals die / fish die /

erosion of buildings / corrosion of bridges; [1] ALLOW: smog / damages buildings NOT: destroys buildings NOT: breathing difficulties / lung damage / irritation to throat / poisonous / harmful [Total: 10]



© UCLES 2009

5 (a) carbon dioxide released / gas is released / gas is formed; [1] NOT: we get carbon dioxide, calcium chloride and water (b) (i) 615 s; [1] ALLOW: in numbers in range 600–630 s (ii) X on or near the line at beginning of experiment; [1] ALLOW: on or near line up to 50 s (iii) shallower curve at initial rate; [1] starts levelling off at 100.2 g; [1] ALLOW: (beginning to) level off between 100.15 and 100.25 g (c) (i) increases / goes faster; [1] NOT: takes less time / becomes fast / reaction increases (ii) increases / goes faster; [1] NOT: takes less time / becomes fast / reaction increases (d) combustion; small; large; [3] (e) (i) respiration; [1] NOT: oxidation (ii) (substance / compound / it) speeds up / increases the rate of a reaction; [1] ALLOW: changes rate of reaction NOT: decreases the rate IGNORE: references to biological substances [Total: 12]



© UCLES 2009

6 (a) Br2; [1] (b) particles random AND roughly similar size to the one shown; [1] particles very close together or touching; [1] (c) Any three of: [3]

• bromine evaporates / liquid evaporates; (NOT: it evaporates)

• more energetic particles from liquid to vapour;

• diffusion;

• random movement of molecules / particles move everywhere / both air and bromine particles are moving;

• (bromine and air) particles get mixed up / collision of bromine and air particles; ALLOW: molecules in place of particles NOT: atoms in place of particles (d) (light) green; [1] IGNORE: yellow to reddish-brown / brown / orange / yellow-brown; [1] NOT: yellow / red (e) bromine higher in reactivity series than iodine / bromine more reactive than iodine; [1] NOT: bromide more reactive than iodide NOT: magnesium bromide more reactive NOT: bromine stronger than iodine (f) (i) NaBr; [1] ALLOW: Na+Br– NOT: multiples e.g. 2NaBr (ii) zinc bromide; [1] ALLOW: zinc(II) bromide NOT: ZnBr2 (iii) covalent; [1] NOT: single bonding (iv) A and D; (both needed) [1] (v) the ions can move / ions are mobile; [1] ALLOW: the ions are free (from each other) NOT: ions delocalised / charged particles moved REJECT: electrons and ions move [Total: 14]



© UCLES 2009

7 (a) Cl2; [1] correct balancing; [1] (b) bonding pair; [1] chlorine electrons all correct and no other electrons on hydrogen; [1] ALLOW: use of circle / dot for chlorine and cross for hydrogen IGNORE: inner electrons (c) pH1; [1] (d) hydrogen; [1] NOT: H2 (e) Any two of: [2]

• evaporate off some of the water / heat solution to crystallisation point; ALLOW: concentrate the solution NOT: boil off the water / implication that all the water is removed NOT: heat without further qualification

• leave to crystallise / leave in the warm / leave in the air / leave on a window sill / leave at room temperature;

NOT: let it cool / leave it to cool

• dry crystals with filter paper; NOT: heat / warm to dry / put in an oven (f) (i) chlorine / Cl2; [1] NOT: Cl (ii) zinc / Zn; [1]

[Total: 10]





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© UCLES 2009

1 (a) (i) basic set up – container and chromatography paper [1] sample clearly above level of solvent [1] (original mark must be shown and not just the line) indication that more than one “spot” either on diagram or as comment [1] Allow MAX [2] for round filter paper with green spot at centre two or more rings (ii) run chromatogram of pure chlorophyll can be implied [1] same position of green spot or same Rf [1] NOT just a green spot (b) catalyst photosynthesis or chloroplasts photochemical reaction or needs light carbon dioxide + water form glucose or starch or oxygen NOT sugar Any THREE correct points ignore incorrect answers [3] [Total: 8] 2 molten potassium iodide NOT aqueous [1] hydrogen [1] oxygen [1] water used up or solution becomes more concentrated or sodium chloride remains NOT no change [1] If products are given as hydrogen, chlorine and sodium hydroxide then 2/3 copper [1] oxygen (and water) [1] sulfuric acid accept hydrogen sulfate [1] aqueous or dilute or concentrated potassium bromide [1] accept correct formulae [Total: 8] 3 (a) (i) D [1] (ii) E [1] (iii) B or F [1] (iv) B [1] (v) A [1]

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© UCLES 2009

(b) (i) CF2 or CaI2 [1] COND next two marks conditional on correct formula C2+ and F– or Ca2+ and I– [1] 7× and 1o round F/I [1] NOTE covalent = 0 Ignore electrons around Ca accept arrow notation arrow from electron on calcium atom to iodine (ii) high melting point or boiling point conducts when molten or in solution soluble in water brittle correct chemical properties hard Any TWO [2] NOT crystalline solid NOT does not conduct as a solid [Total: 10] 4 (i) Cu and Pd [2] (ii) Ba and La [2] (iii) +2 or 2+ or Ba2+ [1] (iv) Ba or La [1] (v) it is a transition metal or a d block element [1] [Total: 7]

5 (a) (i) Ca2+ + 2F– → CaF2 [2] Not balanced ONLY [1] Both species must be correct for first mark. Second mark is for correct balancing. (ii) Mole ratio Ca2+: F– is 1:2 [1] Answer must mention moles accept argument based on charges or number of ions accept 2 moles of NaF react with 1 mole of CaCl2 NOT just “2” in equation If fluorine must specify atoms or ions (iii) to remove traces of solutions or to remove soluble impurities or to remove a named salt sodium chloride or sodium fluoride or calcium chloride [1] To remove impurities is not enough (iv) to dry (precipitate) or to remove water or to evaporate water [1] NOT to evaporate some of water NOT to crystallise salt

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© UCLES 2009

(b) T3(PO4)2 allow correct example [1] explain why 8 cm3 react fully [1] comment about mole ratio [1] [Total: 8] 6 (a) (i) air (liquid) [1] petroleum or crude oil or alkanes or methane or water or steam or steam reforming or

suitable aqueous solution e.g. brine or sea water [1] NOTE: cannot crack methane (ii) iron [1] (iii) (as a) fertiliser or to make fertilisers or to make nitric acid [1] (b) (i) concentrations/macroscopic properties do not change [1] accept amounts stay the same NOT no change rate of forward and back reactions equal [1] (ii) it decreases with increase temperature [1] or it increases with decrease temperature (c) (i) shows an increase either a line or curve [1] (any decrease = 0) (ii) increase pressure favours the side with lower volume or molecules or moles [1] that is RHS or products side [1] ignore any mention of rates [Total: 10] 7 (a) (total endothermic change = 436 + 242 = +)678 kJ [1] (total exothermic change = 2 × 431 = –)862 kJ [1] accept correct sign/supplied/absorbed for endo etc. accept correct sign/evolved/produced for exo etc. change for reaction = –184 kJ [1] not necessary to calculate –184, just show that exo change > than endo ecf allowed provided negative –184 kJ scores all 3 marks (b) (i) because it accepts a proton [2] accepts hydrogen ion or H+ ONLY [1] proton and H+ [2] (ii) hydrogen chloride is a strong acid [1] hydrogen fluoride is a weak acid [1] weaker or stronger correctly applied for [2]

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© UCLES 2009

(iii) hydrogen chloride (aqueous) would have lower pH [1] OR hydrogen fluoride (aqueous) would have higher pH If values suggested, not over 7 [Total: 8] 8 (a) biodegradable or breaks down naturally made from a renewable source or does not use up petroleum reduce visual pollution or reduces need for landfill sites or less danger to wildlife any TWO [2] ignore mention of toxic gases (b) (i) ester [1] accept polyester or fat or lipid or vegetable oil or carboxylic acid (ii) acid or carboxylic acid or alkanoic acid [1] alcohol or hydroxyl or alkanol [1] NOT formulae NOT hydroxide (iii) condensation [1] COND because water is formed in reaction or monomer does not have C=C bond [1]

(c) (i) lactic acid → acrylic acid + water [1] (ii) add bromine (water) or bromine in an organic solvent [1] remains brown/orange/yellow [1] goes colourless NOT clear [1] If mark 1 near miss e.g. bromide allow marks 2 and 3 Colour of reagent must be shown somewhere for [3] otherwise max [2] OR acidified potassium manganate(VII) purple/pink to colourless OR alkaline potassium manganate(VII) purple/pink to green or purple/pink to brown precipitate

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© UCLES 2009

(iii) reagent [1] observable result [1] suitable named metal (NOT sodium, lead, any metal below magnesium etc.) if un-named metal [0] result can score [1] hydrogen evolved or bubbles/effervescence/fizzing insoluble metal oxide colour change or dissolves any carbonate or bicarbonate gas/carbon dioxide/bubbles/effervescence/fizzing sodium hydroxide or alkali temperature increase or accept indicator to show neutralisation unspecified base scores [1] only NOT alcohol [Total: 13] 9 (a) 72/24 = 3 and 28/14 = 2 [1] Mg3N2 [1] accept just formula for [2] even with incorrect or no working NOT ecf (b) Al4C3 + 12H2O = 4Al(OH)3 + 3CH4 [2] For Al4C3 ONLY [1] (c) (i) silicon is limiting reagent [1] 0.07 moles of Si and 25/160 = 0.156 moles of Br2 [1] because 0.14 (2 × 0.07) < 0.156 [1] If 80 used to find moles of Br2 the mark 1 and 3 still available arguments based on masses can be used (ii) 0.07 [1] NOT ecf [Total: 8]

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© UCLES 2009

1 (a) (i) basic set up – container and chromatography paper [1] sample clearly above level of solvent [1] (original mark must be shown and not just the line) indication that more than one “spot” either on diagram or as comment [1] Allow MAX [2] for round filter paper with green spot at centre two or more rings (ii) run chromatogram of pure chlorophyll can be implied [1] same position of green spot or same Rf [1] NOT just a green spot (b) catalyst photosynthesis or chloroplasts photochemical reaction or needs light carbon dioxide + water form glucose or starch or oxygen NOT sugar Any THREE correct points ignore incorrect answers [3] [Total: 8] 2 molten lithium chloride NOT aqueous [1] hydrogen [1] oxygen [1] water used up or solution becomes more concentrated or sodium chloride remains NOT no change [1] If products are given as hydrogen, chlorine and sodium hydroxide then 2/3 copper [1] oxygen (and water) [1] sulfuric acid accept hydrogen sulfate [1] aqueous or dilute or concentrated potassium bromide [1] accept correct formulae [Total: 8] 3 (a) (i) D [1] (ii) E [1] (iii) B or F [1] (iv) B [1] (v) A [1]

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© UCLES 2009

(b) (i) CA or CaO [1] COND C2+ and A2– or Ca2+ and O2– [1] 6× and 2o round anion [1] NOTE covalent = 0 Ignore electrons around Ca accept arrow notation arrow from electron on calcium atom to oxygen (ii) high melting point or boiling point conducts when molten or in solution soluble in water brittle basic(oxide) or basic property hard Any TWO [2] NOT crystalline solid NOT does not conduct as a solid [Total: 10] 4 (i) Cu and Pd [2] (ii) Ba and La [2] (iii) +2 or 2+ or Ba2+ [1] (iv) Ba or La [1] (v) it is a transition metal or a d block element [1] [Total: 7]

5 (a) (i) Fe3+ + 3F– → FeF3 [2] Not balanced ONLY [1] Both species must be correct for first mark. Second mark is for correct balancing. (ii) Mole ratio Fe3+: F– is 1:3 [1] Answer must mention moles accept argument based on charges or number of ions accept 1mole of FeF3 reacts with 3 moles of NaF NOT just “3” in equation If fluorine must specify atoms or ions (iii) to remove traces of solutions or to remove soluble impurities or to remove a named salt sodium chloride or sodium fluoride or iron(III) chloride [1] To remove impurities is not enough (iv) to dry (precipitate) or to remove water or to evaporate water [1] NOT to evaporate some of water

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© UCLES 2009

(b) T3PO4 allow correct example [1] explain why 6 cm3 react fully [1] comment about mole ratio [1] [Total: 8] 6 (a) (i) air (liquid) [1] petroleum or crude oil or alkanes or methane or water or steam or steam reforming or

suitable aqueous solution e.g. brine or sea water [1] NOTE: cannot crack methane (ii) iron [1] (iii) (as a) fertiliser or to make fertilisers or to make nitric acid [1] (b) (i) concentrations/macroscopic properties do not change [1] accept amounts stay the same NOT no change rate of forward and back reactions equal [1] (ii) it increases with increase pressure [1] or it decreases with decrease pressure (c) (i) shows a decrease either a line or curve [1] (any increase = 0) (ii) increase temperature favours the endothermic change [1] that is LHS or reactants side or so less ammonia at equilibrium [1] accept corresponding exothermic argument [Total: 10] 7 (a) (total endothermic change = 436 + 158 = +)594 kJ [1] (total exothermic change = 2 × 562 = –)1124 kJ [1] accept correct sign/supplied/absorbed for endo etc. accept correct sign/evolved/produced for exo etc. change for reaction = –530 kJ [1] not necessary to calculate –530, just show that exo change > than endo ecf allowed provided negative –530 kJ scores all 3 marks (b) (i) because it accepts a proton [2] accepts hydrogen ion or H+ ONLY [1] proton and H+ [2] (ii) hydrogen chloride is a strong acid [1] hydrogen fluoride is a weak acid [1] weaker or stronger correctly applied for [2]

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© UCLES 2009

(iii) hydrogen chloride (aqueous) would have lower pH [1] OR hydrogen fluoride (aqueous) would have higher pH If values suggested, not over 7 [Total: 8] 8 (a) biodegradable or breaks down naturally made from a renewable source or does not use up petroleum reduce visual pollution or reduces need for landfill sites or less danger to wildlife any TWO [2] ignore mention of toxic gases (b) (i) ester [1] accept polyester or fat or lipid or vegetable oil or carboxylic acid (ii) acid or carboxylic acid or alkanoic acid [1] alcohol or hydroxyl or alkanol [1] NOT formulae NOT hydroxide (iii) condensation [1] COND because water is formed in reaction or monomer does not have C=C bond [1]

(c) (i) lactic acid → acrylic acid + water [1] (ii) add bromine (water) or bromine in an organic solvent [1] remains brown/orange/yellow [1] goes colourless NOT clear [1] If mark 1 near miss e.g. bromide allow marks 2 and 3 Colour of reagent must be shown somewhere for [3] otherwise max [2] OR acidified potassium manganate(VII) purple/pink to colourless OR alkaline potassium manganate(VII) purple/pink to green or purple/pink to brown precipitate

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© UCLES 2009

(iii) reagent [1] observable result [1] suitable named metal (NOT sodium, lead etc.) gas/hydrogen/bubbles/effervescence/fizzing if un-named metal [0] result can score [1] insoluble metal oxide colour change or dissolves any carbonate gas/carbon dioxide/bubbles/effervescence/fizzing accept bicarbonate sodium hydroxide or alkali (temperature increase or accept indicator to show neutralisation) unspecified base scores [1] only NOT alcohol [Total: 13] 9 (a) 72/24 = 3 and 28/14 = 2 [1] Mg3N2 [1] accept just formula for [2] even with incorrect or no working NOT ecf (b) Al4C3 + 12H2O = 4Al(OH)3 + 3CH4 [2] For Al4C3 ONLY [1] (c) (i) silicon is limiting reagent [1] 0.08 moles of Si and 7.2/38 = 0.189 moles of F2 [1] because 0.16 (2 × 0.08) < 0.189 [1] If 19 used to find moles of F2 marks 1 and 3 still available arguments based on masses can be used (ii) 0.08 [1] NOT ecf [Total: 8]

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© UCLES 2009

1 Table of results Initial temperature boxes completed correctly i.e. increasing downwards (1) Final temperature boxes correctly completed i.e. lower or the same (1) Average temperature boxes correctly completed (1) Times completed correctly i.e. descending (1) in seconds (1) [5] (a) 5 points correctly plotted (2), –1 for any incorrect smooth line graph is a curve (1) [3] (b) pale yellow/cream/white (1) not cloudy/milky [1] (c) (i) experiment 5 (1) [1] (ii) more energy owtte (1) particles move faster (1) more kinetic energy = 2 more collisions (1) [3] (d) idea of a fair test/to compare effect of changing the temperature (1) [1] (e) (i) value from graph (1) unit (1) extrapolation shown (1) [3] (ii) curve sketched on grid below original curve (1) [1] (f) change e.g. use of data logger/colourimeter (1) or use of lagging/insulation /repeat experiments/use a burette or pipette explanation e.g. timing of reaction more accurate (1) to reduce heat losses /average readings for times/more accurate volumes [2] [Total: 20] 2 tests on solid S (a) black (solid) see (d) (b) effervescence (1) splint ignites/catches fire or glows brighter (1) [2] (c) blue (1) [1] (i) blue (1) precipitate (1) [2] on heating turns brown/black/darkens (1) [1]



© UCLES 2009

(ii) blue (1) precipitate (1) [2] with excess dissolves/clears (1) deep/royal blue (1) [2] (iii) white (1) precipitate (1) [2] (d) black/dark brown solid (1) MUST HAVE (a) correct as well [1] (e) effervescence (1) splint relights (1) ignore pops [2] (f) (i) V is more reactive/faster or converse (1) [1] (ii) oxygen (1) [1] (g) copper (1) oxide (1) reacts with sulfuric acid to form copper sulfate (1) max 2 [2] (h) catalyst/transition metal/manganese oxide (1) [1] [Total: 20]





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© UCLES 2009

1 (a) balance (1) stirring/(glass) rod/stirrer (1) not thermometer beaker (1) [3] (b) (i) excess (1) not residue [1] (ii) filtration/decant (1) not sieve/strain/centrifuge [1] (c) heat/evaporate (1) to crystallising point or description e.g. using glass rod (1) [2] 2 (a) to reach room temperature/be at same temperature owtte (1) [1] (b) insulator/to minimise heat loss (1) [1] (c) exothermic (1) [1] (d) (i) 40 cm3 volume of acid (1) [1] (ii) two straight lines, missing error point (1) extended to intersect (1) [2] (iii) 22.5 +/- 0.5 (1) or read from graph cm3 (1) [2] 3 (a) add dilute acid (1) fizz, no fizz (1) or correct chloride test [2] (b) litmus paper/named indicator (1) turns blue (1) bleached (1) [3] (c) sodium hydroxide/ammonia (solution) (1) green (precipitate) (1) brown (precipitate) (1) [3] 4 (a) Table of results initial temperature boxes completed correctly (2) 24 33 40 51 60 final temperature boxes correctly completed (2) 24 31 38 47 54 average temperature boxes correctly completed (1) 24 32 39 49 57 [5] (b) 5 points correctly plotted (3), –1 for any incorrect smooth line graph (1) [4] (c) (i) experiment 5 (1) [1] (ii) more energy owtte (1) particles move faster (1) more kinetic energy = 2 more collisions (1) [3]



© UCLES 2009

(d) idea of a fair test/to compare effect of changing the temperature (1) [1] (e) (i) value from graph approx 20 (1) unit (1) extrapolation shown (1) [3] (ii) curve sketched on grid below original curve (1) [1] (f) change e.g. use of data logger/colourimeter (1) or use of lagging/insulation /repeat experiments or more values/use a burette or pipette explanation e.g. timing of reaction more accurate (1) to reduce heat losses /average readings for times/volumes more accurate [2] 5 tests on solid S (c) (i) blue precipitate (1) [1] (ii) blue (1) precipitate (1) [2] dissolves/clears (1) deep/royal blue (1) [2] (iii) white (1) precipitate (1) [2] (f) (i) V is more reactive or converse (1) [1] (ii) oxygen (1) [1] (g) catalyst/transition metal/manganese oxide any two points (2) V is a better catalyst = 2 [2] 6 (a) add water (1) crush/mix/warm (1) filter/decant or pipette off liquid/sieve (1) [3] (b) add indicator solution to acid (and note colour) (1) add indicator solution to alkali or named alkali (and note colour) (1) not base conclusion e.g. colours should be different owtte (1) [3]





0620 CHEMISTRY







© UCLES 2010

Question Number

Key Question Number

Key

1 B 21 C

2 A 22 D

3 A 23 C

4 D 24 C

5 A 25 C

6 B 26 D

7 A 27 A

8 C 28 C

9 B 29 D

10 C 30 D

11 A 31 C

12 D 32 A

13 A 33 D

14 C 34 A

15 B 35 B

16 D 36 D

17 D 37 C

18 A 38 B

19 A 39 B

20 C 40 B





0620 CHEMISTRY







© UCLES 2010

Question Number

Key Question Number

Key

1 B 21 C

2 D 22 A

3 B 23 C

4 A 24 C

5 A 25 D

6 A 26 D

7 A 27 C

8 A 28 A

9 D 29 D

10 B 30 C

11 C 31 D

12 C 32 C

13 A 33 B

14 A 34 A

15 D 35 A

16 C 36 D

17 B 37 B

18 D 38 B

19 C 39 B

20 D 40 C





0620 CHEMISTRY







© UCLES 2010

Question Number

Key Question Number

Key

1 B 21 C

2 D 22 A

3 B 23 C

4 A 24 C

5 A 25 D

6 A 26 D

7 A 27 C

8 A 28 A

9 D 29 D

10 B 30 C

11 C 31 D

12 C 32 C

13 A 33 B

14 A 34 A

15 D 35 A

16 C 36 D

17 B 37 B

18 D 38 B

19 C 39 B

20 D 40 C





0620 CHEMISTRY








© UCLES 2010

1 (a) methane [1] (b) methane / propane [1] (c) ammonia [1] (d) oxygen [1] (e) chlorine [1] (f) ethene [1] 2 (a) arrangement: random / far apart OWTTE [1] motion: random / fast / irregular OWTTE [1] (b) two paired electrons and two atoms indicated [1] (c) (i) atom of (same) element with different number of neutrons / atoms with same number of protons and different number of neutrons [1] (ii) number of electrons 1 and 1 [1] number of neutrons for H-1 = 0 [1] number of neutrons for H-3 = 2 [1] number of protons 1 for both [1] (d) exothermic [1] (e) (i) magnesium>zinc>iron>cobalt [2] one pair reversed = 1 mark (ii) calcium chloride; carbon dioxide; water; [3] 3 (a) (i) reversible / decomposition [1] (ii) hydrated; water; [2] (b) (i) any two e.g. conducts electricity / conducts heat / sonorous / shiny etc [2]

(ii) forms coloured compounds / forms ions or compounds with variable oxidation state / good catalyst / high melting point OR high boiling point / forms complex ions [2]

(c) reacts with acids / forms a salt and water with acids [1]



© UCLES 2010

4 (a) chloride / Cl–

[1]

(b) K+ and Br –

(both needed for the mark) [1] (c) 3.5 (g) [1] (d) add (nitric acid and) silver nitrate / lead nitrate [1] yellow ppt [1] (e) (i) I2 [1] (ii) brown / yellowish brown [1] not: grey / black (iii) bromine is more reactive than iodine OWTTE [1] (f) 95 [1] 5 (a) nitrogen; phosphorus; potassium; [3] (b) any two of: plants take up nitrogen / phosphorus / potassium; nitrogen / phosphorus / potassium needs to be replaced; to enable better plant growth / greater yield / otherwise plants won’t grow as well (idea of

increase / more needed) [2] (c) (i) dissolves or idea of dissolving [1] (ii) titration of acid with alkali / last box ticked [1] (d) ammonia [1] (e) (i) calcium oxide / lime [1] allow: calcium hydroxide / limestone / calcium carbonate (ii) plants grow best at certain pH’s / link between pH and plant growth; farmers want to get best yield; OWTTE [2] (f) (i) 4 [1] (ii) 15 [1]



© UCLES 2010

6 (a) haematite [1] (b) (i) Any two of: limestone / coke / air [2] (ii) iron oxide + carbon → iron + carbon monoxide [2] 1 error = 1 mark (iii) each arrow or number in the correct position (1 mark each) [4] (c) ZnS [1] 7 (a) boiling point / first box down ticked [1] (b) fuel oil: fuel for home heating; kerosene: jet fuel; lubricating fraction: waxes and polishes; naphtha: making chemicals; [4] (c) (i) high temperature; catalyst; [2] (ii) C12H26 [1] (iii) correct structure showing all atoms and bonds [1] (d) poly(ethene) allow: polythene [1] (e) (i) steam [1] (ii) substance which speeds up rate / speed of reaction [1] 8 (a) 1st, 3rd and 4th boxes down ticked (aqueous sodium chloride, copper and graphite) [3] (b) insulator [1] (c) (i) anode [1] (ii) negative electrode: zinc [1] positive electrode: chlorine [1] (iii) graphite [1] allow: carbon





0620 CHEMISTRY








© UCLES 2010

1 (a) (i) titanium / vanadium / zirconium / niobium max [2] [2] (1 mark each) allow: symbols (ii) Na / Mg [1] (iii) sodium / Na [1] (iv) potassiu / K [1] (v) vanadium / V [1] (b) O2 [1] correct balance [1] 2 (a) (i) A: giant ionic [1] B: simple atomic [1] C: simple molecular [1] D: metallic [1] (ii) B and C (both needed for mark) [1] (b) solid; molten; [2] 3 (a) coolant / making ethanol / any other names large scale relevant reaction e.g. making sulfuric acid [1] (b) blue / anhydrous cobalt chloride (paper); turns pink; [2] OR white / anhydrous copper sulfate; turns blue; (c) (i) lighted splint; pops / explodes; [2] (ii) pH 12 [1] (d) (i) 3 (CO2); 4(H2O); [2] (ii) combustion [1] (iii) 36 (mg) [1]



© UCLES 2010

4 (a) Any 2 of: diffusion / ink particles move / water particles or molecules move / movement of particles is random / [2] (b) two or more substances (together) that can be separated by physical means [1] (c) (i) ethanol [1] allow: carboxylic acids (ii) oxidation state / third box down ticked [1] (iii) idea of small molecules / monomers joining / repeating units; long chains / large molecules formed; [2] (d) (i) ring around COOH group [1] (ii) removal of oxygen / decrease in oxidation number / addition of electrons [1] 5 (a) filtration / centrifugation [1] allow: decanting (b) C [1] (c) (i) solvent shown in bottom of beaker; [1] spot on the base line vertically below the spots shown; [1] chromatography paper labelled anywhere; [1] (ii) 4 [1] (d) (i) A [1] (ii) bromine water; decolourises / goes colourless; [2] allow: potassium manganate (VII); decolourises; (iii) substance containing carbon and hydrogen only [1] (iv) ethanoic acid [1] (v) alcohols / alkanols [1]



© UCLES 2010

6 (a) conduct heat / conduct electricity / shiny / malleable / ductile max [2] [2] (b) 4 [1] (c) 82 electrons [1] 82 protons [1] 126 neutrons [1] (d) lead + oxygen → lead(II) oxide [1] (e) (i) carbon [1] (ii) gas at room temperature / third box down ticked [1] 7 (a) (i) one of: BMF molecule and diamond a giant covalent structure / [1] BMF has pentagonal (and hexagonal) structure diamond has bent hexagonal or

tetrahedral structure / BMF each carbon joined to 3 others, diamond each carbon joined to four others / (ii) two of: graphite has (flat) hexagonal rings, diamond has bent hexagonal rings or tetrahedral

/ graphite has 3 bonds to each carbon, diamond has 4 / graphite is layered diamond is not / graphite has two types of bonding / forces or weak and strong bonds whereas

diamond has only one type of bond / covalent bonds only [2] (b) covalent [1] (c) layers can slide over each other / forces weak between layers [1] (d) cutting / drilling allow: jewellery [1] (e) any 2 of: carbon dioxide is a greenhouse gas / absorbs infrared radiation / increases global warming / lead to climate change / [2] (f) any two of: sulfur reacts with oxygen (when coal burnt) / forms sulfur dioxide / sulfur dioxide reacts with oxygen (to form sulfur trioxide) / sulfur dioxide or trioxide dissolve in rain (to form acid) / [2]



© UCLES 2010

(g) (i) waste gases from digestion in animals / second box down ticked [1] (ii) correct dot and cross diagram for methane [1] (iii) ethane / propane / butane etc [1] 8 (a) calcium oxide [1] (b) thermal decomposition [1] (c) carbon dioxide has been removed from the limestone / it comes from the limestone [1] (d) neutralising acid soils / treating acidic lakes / flue gas desulfurisation etc [1] (e) temperature of Bunsen / distance of Bunsen from the tube / amount or mass of

carbonate used [1] (f) (i) calcium [1] (ii) 25 cm3 [1] (iii) calcium faster than strontium which is faster than barium / idea of trend down the group; correct trend i.e. less rapid reaction the further down the group; ORA [2] (g) add acid to carbonate; bubble gas or carbon dioxide (evolved) through limewater / test gas or carbon dioxide with limewater; limewater goes milky or cloudy; [3]





0620 CHEMISTRY








© UCLES 2010

1 (i) sulfur [1] (ii) iodine [1] (iii) copper ignore (II) [1] (iv) calcium [1] (v) helium [1] not name of a compound accept correct symbols

2 (i) chloromethane [1] cond biggest molecular mass / biggest mass of one mole / its molecules move slowest / heaviest molecule / highest density [1] accept atomic mass if correct numerical value given ignore it is the heaviest (gas) / biggest molecule accept particles or molecules not atoms (ii) carbon dioxide / calcium carbonate [1] not methane water [1] sodium chloride / brine / seawater [1] (iii) chlorine [1] not chlorine water cond light / UV / heat / high temperature if numerical value given about 200oC / lead tetraethyl [1] not warm (iv) oxygen and nitrogen (in air) [1] not from fuel, negates mark 1 (react) at high temperatures / lightning / in engine [1] not combustion or exhaust, negates mark 2 (v) 2O3 � 3O2 [2] not balanced = [1] 3 (a) (i) bubbles / effervescence / hydrogen / gas pushes up / lifts metal [1] (ii) does not react with acid / zinc and iron react with acid [1] not just unreactive (b) (i) with copper / first experiment [1] (ii) copper acts as a catalyst [1]

(c) (i) smaller gradient [1] not rate is slower (ii) same final volume of hydrogen / same level (on graph) [1]



© UCLES 2010

(d) temperature / heat [1] increase temperature – reaction faster particles have more energy / particles move faster / particles collide more frequently / more particles have enough energy to react not more excited accept arguments for a decrease in temperature [1] powdered greater surface area greater collision rate / more particles exposed (to acid) any two [2] not concentration / light / catalyst / pressure 4 (a) (i) ethanol [1] CH3-CH2-OH [1] propanoic acid [1] CH3-CH2-COOH [1] independent marking, no ecf accept C2H5 not – HO (ii) type of compound – salt / sodium carboxylate / alkanoate [1] not soap / sodium stearate etc use – soap / cleaning / detergent [1] (iii) terylene / PET / Dacron / diolen / mylar / crimplene [1] (b) (i) polyamide / amide / peptide / polypeptide [1] (ii) correct amide linkage NHCO then CONH [1] cond to mark 1, 2 monomers (different shading in box) [1] cond continuation (to ONE correct linkage) [1] OR nylon 6 only one linkage – NHCO [1] cond only one monomer [1] cond continuation (to correct linkage) [1] (iii) use locating agent [1] measure distance travelled by sample / travelled by solvent front [1] cond this is Rf = 0.5 [1] for mark 3, either mark 1 or mark 2 must be awarded accept run a chromatogram of glycine [1] compare with sample same position [1] max [2]



© UCLES 2010

5 (a) (i) macromolecular / giant covalent / giant atomic [1] all atoms held in position / in tetrahedral structure / to four other carbon atoms / all strong bonds [1] (ii) jewellery / drilling / cutting / engraving / cutting edges in scalpels [1] mark first use offered (iii) layer structure / sheets [1] molecules / ions in layers = [0] layers can slide (over each other) [1] (iv) lubricant / pencils / electrodes [1] mark first use offered (b) (i) 4e between carbon and oxygens [1] 2 non-bonding pairs on both oxygens [1] cond correct coding – only scored if marks 1 and 2 awarded [1] ignore O2 in atom (ii) 4O around each Si [1] 2Si around each O [1] must refer to diagram not valencies or electron distributions (iii) SiO2 has higher mp or bp SiO2 is a solid, CO2 is a gas (at rtp) (when both are solids) then SiO2 is harder has higher density SiO2 insoluble, CO2 soluble [2] any two, comparison needed 6 (a) rates equal [1] concentrations do not change / macroscopic properties remain constant [1] accept amounts do not change (b) endothermic [1] cond favoured by high temperatures [1] (c) (i) move to left [1] cond bigger volume / more moles etc [1] do not insist on “gas” (ii) less yellow solid / more brown liquid [1] accept yellow to brown / less solid more liquid / goes brown



© UCLES 2010

7 (a) a transition element has more than one oxidation state or valency [1] accept different oxidation states (b) by removing oxygen concentration of O2 decreases [1] prevents the back reaction / equilibrium shifts to right [1] (c) oxidation number reduced (from (+) 4 to 0) [1] accept accepts electrons or accepts four electrons if number given must be 4 (d) low density / lightweight / light [1] propellers / fittings on ships / inert anodes in electrolysis / hip replacements / ship building / chemical plants / cathodic protection / diving equipment [1] (e) (i) percentage of oxygen = 31.6 % [1] (ii) calculate the number of moles of atoms for each element number of moles of Ti = 31.6/48 = 0.66 number of moles of O = 31.6/16 = 1.98 accept 2 [1] both correct for one mark (iii) the simplest whole number ratio for moles of atoms: Fe : Ti : O 1 1 3 [1] (iv) formula is FeTiO3 accept TiFeO3 [1] must be whole numbers from (iii) or cancelled numbers from (iii) mark ecf throughout



© UCLES 2010

8 (a) same general formula same chemical properties same functional group physical properties vary in predictable way common methods of preparation consecutive members differ by CH2 any two [2] mark first two ignore others unless it contradicts a point which has been awarded a mark (b) (i) 2HCOOH + CaCO3 � Ca(HCOO)2 + CO2 + H2O [2] not balanced = [1] (ii) zinc + methanoic acid � zinc methanoate + hydrogen [2] [1] for each product (iii) protected by oxide layer [1] (c) butanoic acid [1] CH3-CH2-CH2-COOH / C4H8O2 / C3H7COOH / C4H7OOH [1] C2H4O [1] mark ecf to molecular formula





0620 CHEMISTRY








© UCLES 2010

1 In (a), (b) and (c), descriptions of chemical properties need not be detailed. If more than one answer is given in each section, mark the first one and ignore anything subsequent unless it contradicts what they have already written. No marks for reversing physical and chemical properties.

(a) properties should focus on a group 1 metal and not just metals in general

PHYSICAL soft / can be cut (with a knife) / low density / light / low melting point / (good) conductor (heat or electricity) / shiny (when freshly cut) / malleable / ductile / tarnishes [1]

CHEMICAL react with water (not steam) / (very) reactive / forms salts with halogens / react vigorously with acids (ignore concentration) / forms an alkaline or basic oxide / fixed oxidation state or oxidation number or valency of +1 / has one valency or outer shell electron

not forms ionic compounds on its own. [1]

(b) properties should focus on a transition metal

PHYSICAL hard / high density / dense / high mp or bp / (good) conductor (heat or electricity) / strong / malleable / ductile / silver or grey or lustrous or shiny solid [1]

CHEMICAL more than one oxidation state or valency (accept many oxides) / forms coloured compounds or ions (not coloured on its own) / forms complex ions / behave as a catalyst

/ less reactive than group 1 [1]

(c) PHYSICAL colourless gas / yellow gas [1] not diatomic molecules CHEMICAL most reactive halogen / very reactive / forms ionic fluorides / bonds with metals /

form covalent fluorides / bonds with non-metals / powerful oxidant / gains one electron (to be stable) / fixed oxidation state or valency of –1

allow decolourised when reacts with alkene) / forms F– ions / forms acidic oxides / forms an acid when reacted with hydrogen / hydride is acidic [1]

not bleaching agent

2 (a) (i) enzymes are proteins / come from living organisms / biological (catalysts) [1] not enzymes are living or natural

(ii) carbohydrates have 2H:1O ratio [1] contain elements of water [1]

contain water = [1] unless they state that carbohydrates contain water, this response scores 2 or 0

(b) correct -O- linkage [1] cond same correct monomer (this mark is lost if 2 different boxes are shown) [1] cond continuation (i.e. bonds at both ends) [1]

(c) (i) (concentration or amount or mass etc.) of starch decreases (with time) [1] (concentration etc.) of starch becomes zero / all starch gone [1] colour (intensity) indicates how much starch is present (can be inferred) [1] (ii) enzyme denatured / destroyed [1] not enzymes killed / don’t work / saliva denatured



© UCLES 2010

3 (a) (i) red brown or orange to colourless [1] not just bromine decolourised yellow (not dark) / white solid / precipitate / goes cloudy [1] brown to yellow with no mention of solid/precipitate scores = [1] (ii) Br2 + Na2S � 2NaBr + S [1] (iii) look for two comments sulfide (ion) / sulfur (ion) loses electrons [1] not sodium sulfide bromine accepts them [1] (b) (i) oxidation [1] not redox (ii) hydrogen / H2 not H [1] (iii) iron(II) hydroxide / ferrous hydroxide [1] (iv) 4Fe(OH)2 + O2 + 2H2O � 4Fe(OH)3 [1] (v) oxidation number or state or valency increases / electron loss / Fe2+ to Fe3+ [1] not gains oxygen (vi) sacrificial protection or zinc is sacrificed / zinc corrodes not iron or zinc corrodes therefore iron doesn’t / not just zinc rusts zinc is oxidised in preference to iron / zinc reacts with oxygen and water in preference to iron / zinc more reactive or electropositive than iron / zinc forms ions more readily than iron or zinc loses electrons more readily than iron / electrons move on to iron / iron is cathode or zinc is anode / any three [3]



© UCLES 2010

4 (a) (i) same molecular formula / same number of C and H atoms [1] different structural formula or structure [1] same compound = [1]

(ii) correct formula of but-2-ene / methylpropene / methyl cyclopropane [1]

(iii) bromine / bromine water / aqueous bromine [1] brown to colourless not clear [1] stays brown [1] bromide loses the first mark only

OR alkaline potassium manganate(VII) [1] from purple/pink to green/brown [1] stays purple [1]

OR acidic potassium manganate(VII) [1] from purple/pink to colourless not clear [1] stays purple [1]

(b) heat / high temperature (temperature need not be stated, but if it is stated it must be 500ºC or above) [1]

catalyst (need not be named, but if they are named accept any metal oxide or zeolite / aluminosillicates / silicon dioxide) [1] not nickel/platinum

(c) (1,2)dibromobutane [1] if numbers given must be correct butane [1] butanol [1] accept butan-1-ol or butan-2-ol not but-1-ol / but-1-anol / buthanol

5 (a) fractional [1] distillation [1]

(b) (i) O=O / oxygen(–)oxygen / H–H / hydrogen(–)hydrogen [1] (ii) O-H / oxygen(–)hydrogen / OH / bond between hydrogen and oxygen [1] not H-O-H (iii) endothermic. [1]

(c) (i) no pollution / no CO / no CO2 / no oxides of nitrogen / only produces steam or water / no greenhouse gases / no global warming [1] does not use up fossil fuels / water is not a finite resource / water is a renewable source of energy / hydrogen is renewable / available from electrolysis of water [1]

(ii) obtaining hydrogen from water requires fossil fuels / storage problems / transport problems / limited range of vehicles available / gaseous nature means only produces small amount of energy per unit volume / methane as a source of steam reforming is finite / lack of distribution network [1]

not expensive / anything regarding safety / flammability / explosiveness



© UCLES 2010

6 (a) (i) Tl 2S [1]

(ii) TlCl

3 [1] (b) filter / centrifuge / decant wash the precipitate dry the solid / heat the solid (in oven) / press between filter paper [3] all three stated but not in correct order = [2] two out of three stated in any order = [1] (c) (i) silver chloride / silver bromide [1] photography / cameras / films / photo chromic lenses / sunglasses [1] (ii) increase distance between lamp and paper or put lamp far away / put a screen or translucent or semi-opaque material between them / use a less powerful or low voltage or dim lamp / lower the temperature any two [2] (d) (i) thalium sulfate + ammonia + water [1] (ii) 2TlOH + H2SO4 � Tl2SO4 + 2H2O [2] not balanced = [1] incorrect formula = [0] (iii) green precipitate or solid (ignore shades of green but not bluey green etc.) [1] Fe2+ + 2OH– � Fe(OH)2 accept multiples [1] 7 (a) sodium is expensive / difficult to obtain sodium (from sodium chloride) / problems getting

electricity / hard to extract sodium / high energy costs in extraction of sodium [1] (b) (i) reduce temperature / reduce melting point (to 900/1000°C) temperature need not be

stated, but if it is stated it must be within the range better conductivity / solid aluminium oxide does not conduct aluminium oxide is insoluble in water any two [2] (ii) 2O2– � O2 + 4e– [2] or [0] (iii) they burn (away) / react with oxygen / form carbon dioxide [1] (c) hydrogen formed / aluminium above hydrogen in reactivity series / H+ discharged in preference to Al3+ / aluminium is more reactive than hydrogen [1] aluminium more reactive than carbon / carbon cannot reduce aluminium oxide /

aluminium is higher than carbon in the reactivity series / carbon doesn’t reduce aluminium oxide / carbon doesn’t displace aluminium [1]

comparison is essential for mark



© UCLES 2010

8 (a) (i) accept all metals excluding Group I (lithium is acceptable) [1] not lead accept silver (ii) M nitrite / nitrate(III) [1] not nitride (b) (i) exothermic [1] not reverse reaction is endothermic as the question asks about the forward reaction cond forward reaction favoured by low temperature / reverse reaction favoured by high temperature [1] second mark only scores if exothermic is correct. (ii) position of equilibrium to right / forwards / more products / more N2O4 / lighter colour [1] because this side has smaller volume / fewer moles [1] (c) if the final answer is between 86–89% award all 4 if the final answer is between 66–67% award 3 marks (Mr of 32 must have been used) for all other answers marks can be awarded using the mark scheme as below and applying

ecf if necessary number of moles of O2 formed = 0.16/24 = 0.0067/0.00667 or 1/150 number of moles of Pb(NO3)2 in the sample = 0.0133/0.013 or 1/75 mass of one mole of Pb(NO3)2 = 331 g mass of lead(II) nitrate in the sample = 4.4(1) g percentage of lead(II) nitrate in sample = 88.3% (allow 88–89) [4] mark ecf in this question but not to simple integers if mass of lead(II) nitrate > 5.00 only marks 1 and 2 available If divides by 32 (not 24) only last 3 marks can score consequentially





0620 CHEMISTRY








© UCLES 2010

1 In (a), (b) and (c), descriptions of chemical properties need not be detailed. If more than one answer is given in each section, mark the first one and ignore anything subsequent unless it contradicts what they have already written. No marks for reversing physical and chemical properties.

(a) properties should focus on a group 1 metal and not just metals in general

PHYSICAL soft / can be cut (with a knife) / low density / light / low melting point / (good) conductor (heat or electricity) / shiny (when freshly cut) / malleable / ductile / tarnishes [1]

CHEMICAL react with water (not steam) / (very) reactive / forms salts with halogens / react vigorously with acids (ignore concentration) / forms an alkaline or basic oxide / fixed oxidation state or oxidation number or valency of +1 / has one valency or outer shell electron

not forms ionic compounds on its own. [1]

(b) properties should focus on a transition metal

PHYSICAL hard / high density / dense / high mp or bp / (good) conductor (heat or electricity) / strong / malleable / ductile / silver or grey or lustrous or shiny solid [1]

CHEMICAL more than one oxidation state or valency (accept many oxides) / forms coloured compounds or ions (not coloured on its own) / forms complex ions / behave as a catalyst

/ less reactive than group 1 [1]

(c) PHYSICAL colourless gas / yellow gas [1] not diatomic molecules CHEMICAL most reactive halogen / very reactive / forms ionic fluorides / bonds with metals /

form covalent fluorides / bonds with non-metals / powerful oxidant / gains one electron (to be stable) / fixed oxidation state or valency of –1

allow decolourised when reacts with alkene) / forms F– ions / forms acidic oxides / forms an acid when reacted with hydrogen / hydride is acidic [1]

not bleaching agent

2 (a) (i) enzymes are proteins / come from living organisms / biological (catalysts) [1] not enzymes are living or natural

(ii) carbohydrates have 2H:1O ratio [1] contain elements of water [1]

contain water = [1] unless they state that carbohydrates contain water, this response scores 2 or 0

(b) correct -O- linkage [1] cond same correct monomer (this mark is lost if 2 different boxes are shown) [1] cond continuation (i.e. bonds at both ends) [1]

(c) (i) (concentration or amount or mass etc.) of starch decreases (with time) [1] (concentration etc.) of starch becomes zero / all starch gone [1] colour (intensity) indicates how much starch is present (can be inferred) [1] (ii) enzyme denatured / destroyed [1] not enzymes killed / don’t work / saliva denatured



© UCLES 2010

3 (a) (i) red brown or orange to colourless [1] not just bromine decolourised yellow (not dark) / white solid / precipitate / goes cloudy [1] brown to yellow with no mention of solid/precipitate scores = [1] (ii) Br2 + Na2S � 2NaBr + S [1] (iii) look for two comments sulfide (ion) / sulfur (ion) loses electrons [1] not sodium sulfide bromine accepts them [1] (b) (i) oxidation [1] not redox (ii) hydrogen / H2 not H [1] (iii) iron(II) hydroxide / ferrous hydroxide [1] (iv) 4Fe(OH)2 + O2 + 2H2O � 4Fe(OH)3 [1] (v) oxidation number or state or valency increases / electron loss / Fe2+ to Fe3+ [1] not gains oxygen (vi) sacrificial protection or zinc is sacrificed / zinc corrodes not iron or zinc corrodes therefore iron doesn’t / not just zinc rusts zinc is oxidised in preference to iron / zinc reacts with oxygen and water in preference to iron / zinc more reactive or electropositive than iron / zinc forms ions more readily than iron or zinc loses electrons more readily than iron / electrons move on to iron / iron is cathode or zinc is anode / any three [3]



© UCLES 2010

4 (a) (i) same molecular formula / same number of C and H atoms [1] different structural formula or structure [1] same compound = [1]

(ii) correct formula of but-2-ene / methylpropene / methyl cyclopropane [1]

(iii) bromine / bromine water / aqueous bromine [1] brown to colourless not clear [1] stays brown [1] bromide loses the first mark only

OR alkaline potassium manganate(VII) [1] from purple/pink to green/brown [1] stays purple [1]

OR acidic potassium manganate(VII) [1] from purple/pink to colourless not clear [1] stays purple [1]

(b) heat / high temperature (temperature need not be stated, but if it is stated it must be 500ºC or above) [1]

catalyst (need not be named, but if they are named accept any metal oxide or zeolite / aluminosillicates / silicon dioxide) [1] not nickel/platinum

(c) (1,2)dibromobutane [1] if numbers given must be correct butane [1] butanol [1] accept butan-1-ol or butan-2-ol not but-1-ol / but-1-anol / buthanol

5 (a) fractional [1] distillation [1]

(b) (i) O=O / oxygen(–)oxygen / H–H / hydrogen(–)hydrogen [1] (ii) O-H / oxygen(–)hydrogen / OH / bond between hydrogen and oxygen [1] not H-O-H (iii) endothermic. [1]

(c) (i) no pollution / no CO / no CO2 / no oxides of nitrogen / only produces steam or water / no greenhouse gases / no global warming [1] does not use up fossil fuels / water is not a finite resource / water is a renewable source of energy / hydrogen is renewable / available from electrolysis of water [1]

(ii) obtaining hydrogen from water requires fossil fuels / storage problems / transport problems / limited range of vehicles available / gaseous nature means only produces small amount of energy per unit volume / methane as a source of steam reforming is finite / lack of distribution network [1]

not expensive / anything regarding safety / flammability / explosiveness



© UCLES 2010

6 (a) (i) Tl 2S [1]

(ii) TlCl

3 [1] (b) filter / centrifuge / decant wash the precipitate dry the solid / heat the solid (in oven) / press between filter paper [3] all three stated but not in correct order = [2] two out of three stated in any order = [1] (c) (i) silver chloride / silver bromide [1] photography / cameras / films / photo chromic lenses / sunglasses [1] (ii) increase distance between lamp and paper or put lamp far away / put a screen or translucent or semi-opaque material between them / use a less powerful or low voltage or dim lamp / lower the temperature any two [2] (d) (i) thalium sulfate + ammonia + water [1] (ii) 2TlOH + H2SO4 � Tl2SO4 + 2H2O [2] not balanced = [1] incorrect formula = [0] (iii) green precipitate or solid (ignore shades of green but not bluey green etc.) [1] Fe2+ + 2OH– � Fe(OH)2 accept multiples [1] 7 (a) sodium is expensive / difficult to obtain sodium (from sodium chloride) / problems getting

electricity / hard to extract sodium / high energy costs in extraction of sodium [1] (b) (i) reduce temperature / reduce melting point (to 900/1000°C) temperature need not be

stated, but if it is stated it must be within the range better conductivity / solid aluminium oxide does not conduct aluminium oxide is insoluble in water any two [2] (ii) 2O2– � O2 + 4e– [2] or [0] (iii) they burn (away) / react with oxygen / form carbon dioxide [1] (c) hydrogen formed / aluminium above hydrogen in reactivity series / H+ discharged in preference to Al3+ / aluminium is more reactive than hydrogen [1] aluminium more reactive than carbon / carbon cannot reduce aluminium oxide /

aluminium is higher than carbon in the reactivity series / carbon doesn’t reduce aluminium oxide / carbon doesn’t displace aluminium [1]

comparison is essential for mark



© UCLES 2010

8 (a) (i) accept all metals excluding Group I (lithium is acceptable) [1] not lead accept silver (ii) M nitrite / nitrate(III) [1] not nitride (b) (i) exothermic [1] not reverse reaction is endothermic as the question asks about the forward reaction cond forward reaction favoured by low temperature / reverse reaction favoured by high temperature [1] second mark only scores if exothermic is correct. (ii) position of equilibrium to right / forwards / more products / more N2O4 / lighter colour [1] because this side has smaller volume / fewer moles [1] (c) if the final answer is between 86–89% award all 4 if the final answer is between 66–67% award 3 marks (Mr of 32 must have been used) for all other answers marks can be awarded using the mark scheme as below and applying

ecf if necessary number of moles of O2 formed = 0.16/24 = 0.0067/0.00667 or 1/150 number of moles of Pb(NO3)2 in the sample = 0.0133/0.013 or 1/75 mass of one mole of Pb(NO3)2 = 331 g mass of lead(II) nitrate in the sample = 4.4(1) g percentage of lead(II) nitrate in sample = 88.3% (allow 88–89) [4] mark ecf in this question but not to simple integers if mass of lead(II) nitrate > 5.00 only marks 1 and 2 available If divides by 32 (not 24) only last 3 marks can score consequentially





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© UCLES 2010

1 volume for indicator to change colour completed Expt 1 5–10 cm3 ±5 [1] Table of results for Experiment 1 initial temperature box completed correctly (1) other temperature boxes correctly completed (1) i.e. increasing then decreasing comparable to supervisors (1) [3] volume for indicator to change colour completed Expt 2 15–20 cm3 ±5 [1] Table of results for Experiment 2 initial temperature box completed correctly (1) other temperature boxes correctly completed (1) i.e. increasing then decreasing comparable to supervisors (1) [3] (a) all points correctly plotted (3), –1 for any incorrect smooth line graphs or two intersecting straight lines (2) labels (1) [6] (b) value from graph (1) shown clearly (1) [2] (c) pink to colourless not clear [1] (d) (i) experiment 1 [1] (ii) acid C more concentrated (1) stronger (1) more collisions (1) max [2] [2] (e) room temperature or initial temperature from table (1) reaction finished owtte (1) [2] 2 Tests on solid E (a) white/colourless (solid) [1] (b) melts/turns into a liquid/drops of liquid at top of test-tube/steam (1) pH paper turns red/pH 1–4 (1) brown/yellow gas (1) max [2] [2] (c) (i) white (1) precipitate (1) with excess dissolves/clears (1) [3]



© UCLES 2010

(ii) white precipitate (1) insoluble/does not dissolve/no change (1) [2] (iii) pH 1–4 (1) no reaction owtte (1) [2] (iv) effervescence/fizz/bubbles (1) pH paper blue/purple/dark green (1) [2] (d) acid (1) not a sulfate (1) [2] (e) ammonia (1) [1] (f) aluminium (1) nitrate (1) hydrated salt/contains water (1) [3] [Total: 40]





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© UCLES 2010

1 Table of results total volume of water boxes correctly completed (1) temperature boxes completed (1) values decreasing (1) comparable to supervisor’s results (2) ±10 at 10 cm3 ±10 at 16 cm3 [5] (a) appropriate scale for y axis (1) points plotted correctly(4), –1 for each incorrect best fit straight line graph (1) [6] (b) clear liquid formed/no solid visible owtte (1) e.g. no salt left [1] (c) value from graph for 9 cm3 of water (1) ±½ small square extrapolation of straight line shown (1) [2] (d) sketch graph below line (1) label (1) [2] (e) temperatures at which crystals appear lower (1) solution more dilute in same volume of water/less saturated owtte (1) [2] temperature halved as half as much solid = 2 (f) one improvement from e.g. don’t use a beaker of cold water to cool solution/ do not remove thermometer from the solution/ use second person/or IT method to note formation of crystals repeat linked explanation different rate of heat losses/ loss of solid on thermometer/ observing formation of first crystals may vary average [2]



© UCLES 2010

2 (a) Tests on solid W yellow (1) precipitate (1) not solid [2] (b) Tests on solution X (i) blue (1) [1] pH of solution X approx 1–4 (1) [1] (ii) blue (1) precipitate (1) [2] (iii) blue precipitate (1) darker/deep/royal blue (1) solution (1) or precipitate dissolves/goes clear [3] (iv) brown (liquid/solution) (1) cream/white (1) solid/precipitate (1) [3] (c) Tests on solution Y (i) pH 1–3 (1) [1] (ii) white (1) precipitate (1) [2] (d) iodide or I-(1) not iodine [1]

(e) copper (1) acidic (1) [2] (f) sulfate only (1) acid only (1) sulfuric acid (2) max [2] [2] [Total: 40]





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© UCLES 2010

1 (a) flask (1) tap/separating/dropping funnel (1) not burette gas jar (1) accept measuring cylinder [3] (b) gas should be collected downwards owtte (1) [1] (c) to remove impurities/water (1) [1] 2 wrong reagent, correct result = 0 aqueous sodium iodide (nitric acid)/silver/lead nitrate (1) yellow precipitate (1) hexene bromine (water) (1) goes colourless (1) not clear accept lit splint burns nitric acid named indicator (1) correct colour change/pH (1) or magnesium forms hydrogen/fizzes or (named) carbonate forms carbon dioxide/fizzes [6] 3 (a) volumes completed correctly 0, 60, 68, 95, 98, 99, 100 –1 for each incorrect [4] (b) points plotted correctly (3) –1 for each incorrect smooth curve (1) [4] (c) point at 2 minutes (1) off curve owtte (1) [2] (d) steeper curve (1) levels out at same volume (1) [2]



© UCLES 2010

4 (a) Table of results for Experiment 1 temperature boxes completed correctly (2), –1 for each incorrect [2] 23 33 35 33 31 29 27 (b) Table of results for Experiment 2 temperature boxes completed correctly (2), –1 for each incorrect [2] 23 25 27 26 25 24 23 (c) all points correctly plotted (3), –1 for any incorrect smooth line graphs (2) or two intersecting straight lines labels (1) [6] (d) value from graph ±1 small square (1) shown clearly (1) [2] (e) (i) experiment 1 (1) [1] (ii) acid C more concentrated (1) stronger (1) more collisions (1) max [2] [2] (f) to clean it/remove acid C owtte (1) [1] (g) room temperature or initial temperature from table (1) reaction finished owtte (1) [2] 5 tests on solid E (c) (i) white (1) precipitate (1) with excess dissolves/clears/colourless (1) [3] (ii) white precipitate (1)

insoluble/no change (in excess) (1) [2]



© UCLES 2010

(d) contains water/hydrated (1) [1]

(e) ammonia (1) not ammonium [1]

(f) nitrate (1) hydrated salt (1) not a sulfate (1) max [2] [2] 6 (a) arrow must be underneath solid in tube (1) [1] (b) red/pink to blue (1) [1] (c) to cool/condense (the water/steam) (1) [1] (d) pressure would build up/air or gases needs to escape owtte (1) [1]

7 crush malachite (1) using pestle/mortar (1) add named acid (1) solution formed (1) add magnesium/zinc/iron (1) displacement (1) obtain copper/filter (1) max [6] [6] or first two steps (2) add carbon/reactive metal/hydrogen (1) heat (1) displace/redox (1) until goes pink (1) obtain copper (1) or first four steps (4) electrolyse solution (1) copper deposited at cathode (1) obtain copper (1) NB If malachite anode used allow max 3 even if it would not work. [Total: 60]





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© UCLES 2010

1 (a) Bunsen (burner) (1) tripod (1) condenser (1) [3] (b) (i) F (1) allow description (ii) G (1) allow description [2] 2 (a) pestle and/or mortar (1) accept diagram not bowl/crusher [1] (b) pour off/out liquid owtte (1) not separate/filter [1] (c) chromatography/chromatogram (1)

apply solution to paper (1) use of (named) solvent (1) not water conclusion/results/spots at different levels (1) all marks can be scored from a labelled diagram dipping paper in green solution = max 2 [4]

3 (a) volumes completed correctly

0, 20, 26, 41, 45, 46 –1 for each incorrect [3] (b) points plotted correctly including origin (3) –1 for each incorrect

smooth curve (1) [4] (c) point at 2 minutes (1)

off curve owtte (1) [2] (d) steeper curve (1) levels out at same volume (1) [2]



© UCLES 2010

4 (a) Table of results for Experiment 1 temperature boxes completed correctly (2), –1 for each incorrect [2] 23 25 27 26 25 24 23

(b) Table of results for Experiment 2

temperature boxes completed correctly (2), –1 for each incorrect [2] 23 33 35 33 31 29 27

(c) all points correctly plotted (3), –1 for any incorrect

smooth line graphs (2) or two intersecting straight lines labels (1) [6]

(d) value from graph ±1 small square (1) shown clearly (1) [2] (e) (i) experiment 2 (1) [1] (ii) acid D more concentrated (1)

stronger (1) more collisions (1) max [2]

(f) to clean it/remove acid C owtte (1) [1]

room temperature or initial temperature from table (1) reaction finished owtte (1) [2]

5 Tests on solid E (c) (i) white (1) precipitate (1)

no change with excess/insoluble (1) [3] (ii) no reaction/thin/slight precipitate (1) [1] (d) contains water/hydrated (1) [1] (e) not a sulfate (1) accept not a carbonate [1] (f) ammonia (1) not ammonium [1] (g) nitrate (1)

hydrated salt (1) not a sulfate (1) not a carbonate (1) max [2] [2]



© UCLES 2010

6 (a) electrolysis (1) [1] (b) platinum/graphite/carbon (1) [1] (c) (blue) litmus/universal indicator paper/pH paper (1)

bleaches/turns white (1) [2] (d) hydrogen (1) [1] 7 add (named) acid/water/salty water to piece of copper/steel (1)

heat (1) for specified/same time (1) observe reaction/effect (1) repeat with other metal (1) compare metals (1) [6] no reagents = 0 marks or heat metal (1) repeat with other metal (1) method for measuring conductivity (1) max [3] [3]

[Total: 60]





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© UCLES 2010

1 (a) Bunsen (burner) (1) tripod (1) condenser (1) [3] (b) (i) F (1) allow description (ii) G (1) allow description [2] 2 (a) pestle and/or mortar (1) accept diagram not bowl/crusher [1] (b) pour off/out liquid owtte (1) not separate/filter [1] (c) chromatography/chromatogram (1)

apply solution to paper (1) use of (named) solvent (1) not water conclusion/results/spots at different levels (1) all marks can be scored from a labelled diagram dipping paper in green solution = max 2 [4]

3 (a) volumes completed correctly

0, 20, 26, 41, 45, 46 –1 for each incorrect [3] (b) points plotted correctly including origin (3) –1 for each incorrect

smooth curve (1) [4] (c) point at 2 minutes (1)

off curve owtte (1) [2] (d) steeper curve (1) levels out at same volume (1) [2]



© UCLES 2010

4 (a) Table of results for Experiment 1 temperature boxes completed correctly (2), –1 for each incorrect [2] 23 25 27 26 25 24 23

(b) Table of results for Experiment 2

temperature boxes completed correctly (2), –1 for each incorrect [2] 23 33 35 33 31 29 27

(c) all points correctly plotted (3), –1 for any incorrect

smooth line graphs (2) or two intersecting straight lines labels (1) [6]

(d) value from graph ±1 small square (1) shown clearly (1) [2] (e) (i) experiment 2 (1) [1] (ii) acid D more concentrated (1)

stronger (1) more collisions (1) max [2]

(f) to clean it/remove acid C owtte (1) [1]

room temperature or initial temperature from table (1) reaction finished owtte (1) [2]

5 Tests on solid E (c) (i) white (1) precipitate (1)

no change with excess/insoluble (1) [3] (ii) no reaction/thin/slight precipitate (1) [1] (d) contains water/hydrated (1) [1] (e) not a sulfate (1) accept not a carbonate [1] (f) ammonia (1) not ammonium [1] (g) nitrate (1)

hydrated salt (1) not a sulfate (1) not a carbonate (1) max [2] [2]



© UCLES 2010

6 (a) electrolysis (1) [1] (b) platinum/graphite/carbon (1) [1] (c) (blue) litmus/universal indicator paper/pH paper (1)

bleaches/turns white (1) [2] (d) hydrogen (1) [1] 7 add (named) acid/water/salty water to piece of copper/steel (1)

heat (1) for specified/same time (1) observe reaction/effect (1) repeat with other metal (1) compare metals (1) [6] no reagents = 0 marks or heat metal (1) repeat with other metal (1) method for measuring conductivity (1) max [3] [3]

[Total: 60]





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• Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May/June 2011 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.





Question Number

Key Question Number

Key

1 D 21 C

2 A 22 B

3 B 23 B

4 C 24 D

5 C 25 D

6 A 26 A

7 C 27 A

8 D 28 C

9 B 29 A

10 C 30 B

11 A 31 C

12 B 32 D

13 B 33 D

14 B 34 A

15 C 35 D

16 B 36 C

17 C 37 C

18 B 38 B

19 B 39 D

20 B 40 A





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Question Number

Key Question Number

Key

1 D 21 B

2 A 22 B

3 C 23 B

4 A 24 B

5 B 25 C

6 C 26 D

7 A 27 D

8 B 28 A

9 C 29 A

10 B 30 A

11 C 31 D

12 D 32 C

13 B 33 D

14 C 34 A

15 B 35 D

16 B 36 D

17 C 37 A

18 B 38 C

19 C 39 B

20 B 40 C





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Question Number

Key Question Number

Key

1 D 21 B

2 A 22 B

3 C 23 B

4 A 24 B

5 B 25 C

6 C 26 D

7 A 27 D

8 B 28 A

9 C 29 A

10 B 30 A

11 C 31 D

12 D 32 C

13 B 33 D

14 C 34 A

15 B 35 D

16 B 36 D

17 C 37 A

18 B 38 C

19 C 39 B

20 B 40 C





0620 CHEMISTRY









1 (a) E / nitrogen (di)oxide / NO2 [1] (b) B / potassium nitrate / KNO3 [1] (c) A / ammonia / NH3 [1] (d) E / nitrogen(di)oxide / NO2 [1] (e) C / NCl3 / nitrogen (tri)chloride [1] (f) B / potassium nitrate / KNO3 [1] 2 (a) atoms of same element with different number of neutrons / same type of atom with different

mass number / atoms with same proton number but different number of neutrons / atoms with same proton number but different nucleon number/ atoms with same atomic number but different nucleon number [1]

(b) 23 protons [1] 23 electrons [1] 27 neutrons [1] (c) non [1] medicine [1] cancer [1] (d) 2nd box ticked [1] 5th box ticked [1]




3 (a) anhydrous copper sulfate / white copper sulfate [1] ignore oxidation numbers turns blue [1] OR anhydrous cobalt chloride / blue cobalt chloride (1 mark) ignore oxidation numbers turns pink (1 mark) note second mark is dependent on the first being correct BUT cobalt chloride turns pink = 1

mark (b) coolant / solvent / hydroelectric power [1] allow for cooling / to cool allow specific reactions e.g. making sulfuric acid / making ethanol allow: for washing or cleaning if specific industrial process mentioned allow for agriculture / for growing crops (on a large scale) / brewing ignore for cooking / for drinking / for power (unqualified) / for watering plants / for cooling food (c) substance OR liquid which dissolves another (substance) / substance which does the dissolving [1] ignore it dissolves / it is a liquid / names of solvents (d) (i) burning coal / burning fossil fuels / burning petrol petrol / burning specified fuel (as long

as it contains sulfur) / from volcanoes / from heating sulphide ores [1] ignore burning pure substances e.g. hydrogen, methane / car exhausts ignore from ores without qualification / (ii) any two effects (1 mark each) e.g. [2]

• forest death / kills trees / deforestation / destroys trees / damages trees ignore kills plants / rots trees / kills crops

• acidification of lakes / acidification of rivers ignore acidifies soils

• kills fish / aquatic plants / plant in lakes or rivers ignore kills fish or plants in the sea / kills animal (unqualified) / kills plants (unqualified)

• erodes buildings made from limestone / erodes carbonate rocks / damages buildings made from limestone / damages carbonate rocks allow destroys building made from limestone / destroys carbonate rocks ignore just erosion of buildings or rocks unqualified / dissolves buildings / chemical weathering

• corrosion of metal structures / corrosion of named metal structures e.g. bridges or railings / damages metal structures allow erosion of metal structures / damaging metal structures / destroys metal structures / reacts with metals ignore dissolves metals ignore effects on humans

(iii) 64 (g) [1]




(e) In each of these points, the explanation mark depends on the correct step filtration or words to that effect [1] removal of undissolved substances / solids / impurities get trapped / removes insoluble impurities [1] allow removes dirt ignore solids which would sediment rapidly or are large e.g. pieces of metal, batteries, twigs etc. / removes impurities chlorination / adding chlorine [1] allow chlorification kills bacteria [1] allow kills microbes / kills germs / disinfection / sterilisation ignore kills bugs / removes bacteria allow other stages with correct explanation e.g. screening (1 mark) removing large objects / removing twigs etc. (1 mark) sedimentation (1 mark) allowing particles to settle (1 mark) adding carbon (1 mark) removes tastes / removes smells (1 mark) flocculation (1 mark) coagulates clay / makes small particles clump together (1 mark) lime (1 mark) idea of neutralisation or removal of acids (1 mark)

(f) (i) 20 (%) allow 19–21 (%) [1] (ii) 28 (g) [1]




4 (a) (i) D [1] (ii) B [1] (iii) E [1] (iv) C [1] (b) (i) 4 (H2O) [1] 5 (O2) [1] note 2nd mark dependent on 4 (H2O) being correct (ii) any 2 of: carbon monoxide / carbon allow soot water allow correct formulae [2] (c) O ║ - C – O – H [1]




5 (a) breakdown (of substance / electrolyte) by electricity / splitting up of substance by electricity / decomposition by electricity [1]

allow current / voltage for electricity ignore separation by electricity / division by electricity note idea of breakdown AND idea of current / electricity for the mark (b) anode [1] (c) hydrogen [1] allow H2 (d) platinum [1] inert [1] (e) (i) 2,8,7 as numbers or as shown in electron shell diagram [1] (ii) pair of electrons between two chlorine atoms [1] rest of electrons correct [1] ignore inner shells (iii) (damp) litmus (paper) / universal indicator (paper) [1] allow indicator paper / pH paper bleaches / goes white [1] allow goes red then bleaches reject changes colour of bromides / iodides (f) (i) calcium chloride + water (1 mark each) [2] apply listing for extra elements / compounds allow correct formulae (ii) H2 on right [1] ignore numbers in front of H2 unless equation balanced 2 on left [1]




6 (a) (i) copper → zinc → magnesium → calcium [1] (ii) cold water → no reaction [1] steam → fairly rapid / moderately rapidly / moderately / slowly / very slowly ignore less rapidly than zinc / more rapidly that copper / it reacts [1] reject rapidly (b) zinc + water → zinc oxide + hydrogen [1] allow steam in place of water (c) Any three of: [3]

• conducts electricity • conducts heat • malleable / can be bent • ductile / • shiny / lustrous • sonorous / rings when hit • solid

ignore reference to melting point / boiling point / density / strength ignore colours e.g. grey (d) (i) allow any figures in the range 120–200°C [1] (actual = 181°C) (ii) less hard (down the Group) / softer (down the Group) [1] allow decreases (in hardness) ignore from hard to soft / the softer is at the bottom and the harder at the top / gets softer

as melting point decreases (iii) allow any figures in the range 0.7–1.3 (g / cm3) [1] (actual = 0.86)




7 (a) top left box → oxygen [1] bottom right box → slag [1] bottom left box → (molten) steel [1] (b) (i) they are gases / gases escape easily / sulphur oxides are gases / named sulfur oxides

are gases / carbon dioxide is a gas / named oxide of carbon is gas / the products are gases [1]

(ii) any three of:

• phosphorus(V) oxide is acidic oxide ignore it is acidic

• calcium oxide is basic oxide • idea of calcium oxide neutralising OR reacting with phosphorus oxide

allow they combine together / they react together / it reacts with the phosphorus oxide

ignore they react (unqualified) • slag formed (by the reaction) / slag is removed [3]

(c) (i) D [1] (ii) any suitable use e.g. chemical plant / cutlery / surgical instruments / (ball) bearings / [1]

allow facings of buildings (not buildings without qualification) parts of aircraft engines (not aircraft without qualification) bridges car decoration / trim / radiator grills / exhaust pipes (not cars without qualification) washing machine drums razor blades chemical tankers / road tankers (not tankers unqualified) cooking utensils ignore for cooking watches




8 (a) any three of [3] • particles move faster / in liquid particles move slowly AND in gas they move rapidly • particles more spread out / in liquid particles are touching (or very close) AND in gas

they are far apart • particles more randomly arranged / in liquid the particles have some order AND in gas

the particles are random • particles move more freely / in liquid particles do not move freely AND in gases particles

are freely moving / in liquid particles have limited motion (or slide over each other) AND in gases particles are free

(b) (i) chlorine + (bromide ions) → chloride (ions) + bromine [1] allow correct symbols (ii) vaporises easily / forms a gas easily [1] allow vaporises (very) fast / evaporates (very) fast / low boiling point reject ideas of reaction (c) (i) substance which speeds up reaction / makes reaction go faster / lowers the activation

energy [1] allow changes rate of reaction ignore slows down reaction (ii) it gains hydrogen / oxygen accepts hydrogen / hydrogen peroxide accepts hydrogen /

oxidation number of oxygen decreases [1] allow it loses oxygen / hydrogen peroxide loses oxygen / hydrogen peroxide gains

electrons / oxygen gains electrons ignore comments related to hydrogen bromide alone (iii) sodium bromide [1] carbon dioxide AND water [1] [Total: 80]





0620 CHEMISTRY









1 (a) (i) C [1] (ii) B [1] (iii) E [1] (iv) C [1] (v) D [1] (vi) A [1] (b) (i) electrons [1] atoms [1] (ii) 1st box from left ticked [1] 2 (a) (i) iron → nickel → zinc → aluminium [1] (ii) too reactive / takes too much energy / too high temperature needed [1] (iii) bauxite [1] (b) (i) air [1] limestone [1] allow calcium carbonate (ii) 3 (CO) [1] 2 (Fe) [1] apply listing for extra incorrect additions to equation (iii) carbon dioxide [1] loses oxygen [1] allow oxidation number of carbon in carbon dioxide decreases allow carbon gains electrons ignore electrons gained unqualified (iv) poisonous / toxic [1] ignore harmful (v) takes in heat / energy (from surroundings) [1] allow temperature of the reaction mixture / surroundings falls allow temperature goes down (c) (i) mixture of metals / mixture of metal with non-metal OR carbon [1] (ii) any suitable e.g. for car bodies / bridges / girders / railings etc. [1] allow e.g. nuts / bolts / bullets / chains / hinges / knives / pipes / magnets / road signs /

wire (for fences) / cans etc. ignore for building without qualification




3 (a) (i) 80 (%) [1] allow 79–81 (ii) any two of: [2] carbon dioxide / argon / neon / xenon allow helium / radon / water vapour reject hydrogen (b) (i) decreases / gets less / gets lower [1] (ii) increases / gets more / greater [1] (c) any suitable use e.g. electrical conductor / electrical wiring / saucepans [1] not wires unqualified (d) electrolyte is soluble copper salt / named soluble copper salt e.g. copper sulfate [1] the spoon is the cathode / the copper rod is the anode [1] accept implication of this e.g. the positive ions move to the spoon spoon gets coated with copper / spoon becomes brown [1] 4 (a) (i) carbon dioxide [1] allow CO2 (ii) any one of: [1]

• room temperature OR temperature quoted from 20–40°C / ignore low temperature / high temperature

• yeast / enzymes / zymase ignore catalyst alone ignore microbes / viruses / bacteria

• absence of oxygen / anaerobic • pH 7 / pH near neutral

(b) (i) H – O – H [1] not H2O H H │ │ H – C – C – O – H [1] │ │ H H allow – OH in place of – O – H not C2H5OH (ii) aqueous bromine / bromine water [1] allow bromine / aqueous (acidified) potassium permanganate turns colourless / decolourises [1] ignore goes clear




(c) carbon dioxide [1] water [1] (d) homologous [1] similar [1] functional [1] 5 (a) diamond: covalent (bonding) [1] giant structure allow macromolecule [1] chlorine: any two of: [2]

• molecule • covalent • diatomic

(b) C6Cl12 [1] (c) (i) green / yellow green / light green [1] reject bluish-green / yellow alone (ii) allow values between 2.5–4.0 (actual = 3.12) [1] (iii) increases [1] reject decreases then increases (d) (i) iodine [1] allow I2 potassium bromide [1] allow KBr (ii) chlorine is more reactive than bromine / bromine is less reactive than chlorine / [1] ignore chlorine is higher in the group reject chloride / chloride is more reactive than bromide (e) ionic compounds soluble AND molecular not (soluble) [1] (both needed for mark) ionic compounds conduct electricity when molten / in (aqueous) solution AND molecular ones do not [1] (both needed for mark)




6 (a) any three of: [3] • add excess iron to sulfuric acid / • filter off (excess) iron / • concentrate filtrate / iron sulfate solution OR heat filtrate to crystallisation point

allow heat filtrate so that some of water evaporated allow leave on windowsill for water to evaporate / allow water to evaporate ignore heat filtrate without qualification

• filter off crystals / pick out crystals / • dry crystals with filter paper

(b) (i) oxidation number / iron forms 2+ ions [1] allow charge on the iron ion (ii) add (aqueous) sodium hydroxide [1] green [1] precipitate [1] (iii) water was given off / iron sulfate lost water / dehydration (reaction) [1] (iv) double headed arrow / equilibrium sign [1] (c) (i) turns red / pink [1] bubbles / effervescence [1] allow iron disappears / tube gets hot / solution turns light green ignore hydrogen given off / gas given off (ii) so plants can grow better / so crops can grow better / plants cannot grow well in alkaline

conditions [1] (iii) pH 8 [1] (iv) calcium oxide / lime / limestone / chalk / calcium carbonate [1] allow slaked lime




7 (a) (i) any value between 15–35 seconds [1] (ii) any three of: [3]

• particles escape from (ammonium) carbonate or solid allow particles evaporate from (ammonium) carbonate /

• diffusion / • particles are in random motion / • particles gradually mix up (with air particles) / • particles spread out everywhere / • particles collide with air particles /

(b) 96 [1] (c) (i) nitrogen phosphorus potassium (1 mark for each) [3] NPK = 2 marks (ii) 3rd box down ticked [1] (d) 330 (g) [1] [Total: 80]





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1 (a) F or B diffusion / fractional distillation [1] (b) A simple distillation [1] (c) D chromatography [1] (d) E filtration [1] (e) C evaporation [1] (f) B fractional distillation [1] 2 (a) (i) photosynthesis or a photochemical reaction [1] not an example, question requires a process not devices which convert light into electricity (ii) cell [1] accept battery not generator (b) (i) correct formula [1]

cond following marks conditional on correct formula If covalent mark 1 only correct charges [1] 6x and 2o around anion [1] do NOT penalise for incorrect coding ignore electrons around potassium

(ii) correct formula [1]

If ionic mark 1 only cond 2 bp and 2 nbp around selenium [1] 1 bp and 3 nbp around both chlorine atoms [1]

(iii) the ionic compound

higher melting point / boiling point / less volatile conducts when molten or aqueous, covalent compound does not is soluble in water, covalent is not / ionic insoluble in organic solvents, covalent soluble in organic solvents harder any two [2] note there has to be comparison between the ionic compound and the covalent compound not density




(c) base [1] not alkali accepts a proton [2] accepts hydrogen ion / H+ only [1] proton and H+ [2] 3 (a) any four max 4

carbon forms carbon dioxide / carbon monoxide [1] this is a gas it escapes / blown out / diffuses [1] silicon forms silicon(IV) oxide / silica [1] / silicon(IV) oxide present in impure iron silicon(IV) oxide reacts with calcium oxide to form slag or calcium silicate [1] slag removed from surface [1] accept skimmed, syphoned, poured off not tapped max [4] accept correct formula or equations not calcium oxide reacts with silicon

(b) (i) any sensible suggestion – harder/stronger/can be tailored for a specific use/more

resistant to corrosion [1] not steel does not rust (ii) mild steel – cars or any vehicle/bicycles/white goods/screws or nails/roof/bridges/tools/

buildings/ships/pipes/machinery etc. [1] stainless steel – chemical plants/cooking utensils/jewellery/cutlery/surgical equipment/

kitchen sinks/pipes/etc. [1] (c) (i) strong attractive forces / strong bonds / bonds hard to break / requires a lot of

energy to break bonds [1] not between ions, not between positive and negative ions, not between electrons between positive ions and (negative) electrons / opposite charges attract [1]

(ii) because the layers, lattice or rows of ions/cations [1]

accept sheets of ions not atoms / molecules / protons / nuclei can move / slip / slide past each other [1]

4 (a) (i) 2ZnS + 3O2 → 2ZnO + 2SO2 [2] not balanced only [1] (ii) two reagents from named metal(s) more reactive than zinc/carbon monoxide [2] not hydrogen (iii) they have different boiling points [1] cadmium will distil first then zinc leaving lead/lead distilled last [1]




(b) for a high yield need low temperature [1] then rate would be too slow or uneconomic [1] a discussion of optimum temperature could score mark 1 and 2 presence of catalyst would increase rate (at same temperature) [1] does not alter the yield (at that temperature) [1] / economic rate at lower temperature, therefore higher yield higher pressure which would increase yield / rate [1] yield high enough / high pressure expensive [1] max [4] accept reverse arguments

note increase yield X position of equilibrium to right

5 (a) (i) 2Li + 2HI → 2LiI + H2 [1]

(ii) zinc carbonate + hydriodic acid → zinc iodide + carbon dioxide + water [1]

(iii) MgO + 2HI → MgI2 + H2O [1] (b) reaction 1 is redox / Li/2HI reaction [1] cond reason either oxidation number/state / electron transfer [1] (c) with hydriodic acid – iodine formed / goes dark brown / grey/black solid [1] not purple vapour not purple/black solution with hydrobromic acid – bromine formed / goes orange / yellow / brown / reddish brown / red

/ brown vapour [1] note can accept brown for iodine provided bromine is different orange/brown etc. (d) (i) the reaction is exothermic / reaction produces heat/energy [1] all the sodium hydroxide used up/neutralised / reaction has stopped [1] (ii) adding colder acid / no more heat produced [1] if not given in (d)(i) any comments such as “reaction has stopped” can gain mark (iii) 1.33 / 1.3 / 1.3333 (mol/dm3) scores both marks [2] not 1.34 for a correct method – M1 V1 / moles of NaOH = 0.02 with an incorrect answer only [1]




6 (a) (i) cracking / heat with catalyst [1] to make butane [1] butene reacts with steam/water / hydrated [1] accept heat and catalyst for cracking but if specified: 450 to 800°C zeolites / aluminosilicates / silica / aluminium oxide/alumina / china / broken pot / porcelain / chromium oxide

(ii) glucose / sugar changed to alcohol / ethanol [2]

accept an unbalanced equation (catalysed by) enzymes / yeast [1]

(b) butanoic acid [1] CH3-CH2-CH2-COOH [1] hydrogen atoms omitted from ends of bonds, penalise once (c) (i) ester [1] (ii) C6H12O2 ignore CH3COOC4H9 [1] (iii) correct structural formula of butyl ethanoate showing all bonds [2] 7 (a) metal A is magnesium [1] cond most reactive or fastest reaction [1] metal B is aluminium [1] cond faster reaction after removal of oxide layer / it would give more hydrogen / aluminium

more reactive than zinc [1] metal C is zinc [1] zinc least reactive [1] NOTE MAX [5] If you encounter different reasoning which is correct, please award the appropriate marks. (b) for magnesium and zinc same volume of hydrogen [1]

because both have valency of 2 / 1 mole of metal gives 1 mole of hydrogen / 1 mole of metal reacts with 2 moles of acid [1] bigger volume for aluminium because its valency is 3 / 1 mole of metal gives 1.5 moles of hydrogen / 1 mole of metal reacts with 3 moles of acid [1] If you encounter different reasoning which is correct, please award the appropriate marks. accept balanced equations accept ionic charges as alternative to valency




8 (a) addition – polymer only product / only one product [1] accept monomer has C=C accept monomer and polymer have same empirical formula accept no loss of material in polymerisation not only one monomer condensation – polymer and water / small molecule formed [1]

(b) -CH2 – CCl2- repeat unit correct [1] COND continuation [1] (c) CH2=CHOOCCH3 [1] (d) -OC(CH2)4CONH(CH2)6NH-

COND amide correct linkage [1] correct repeat units [1] continuation [1] not NH2 or COOH endings

[Total: 80]





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1 (i) Rb / Sr [1] (ii) I [1] (iii) Fe [1] (iv) P [1] (v) Si [1] 2 (a) (i) no reaction [1]

Fe + Sn2+ → Fe2+ + Sn / 2Fe + 3Sn2+ → 2Fe3+ + 3Sn [2] for realising that there would be a reaction shown by an attempt to write an equation e.g. writing Fe2Sn etc. allow [1] no reaction [1]

(ii) tin oxide, nitrogen dioxide (accept nitogen(IV) oxide/dinitrogen tetroxide), oxygen All three for two [2] accept correct formulae any two correct products [1] (b) (i) tin [1]

(ii) 4OH– → O2 + 2H2O + 4e– [2] not balanced allow [1] (iii) sulfuric acid [1] (c) zinc is more reactive than iron/steel [1]

tin is less reactive than iron/steel [1] zinc corrodes/reacts/loses electrons/is oxidised/is anodic/provides sacrificial protection/ forms positive ions (in preference to iron or steel) ORA allow iron is cathodic for this mark. [1] Iron/steel corrodes/reacts/rusts/loses electrons/is oxidised/is anodic/forms positive ions (in preference to tin). ORA allow tin is cathodic for this mark [1]




3 (a) (i) concentration of thiosulfate is proportional to volume of thiosulfate solution added (when total volume is same in all experiments) / concentration of acid always the same [2] for comments based on amount / to make experiments fair / comparable allow [1]

(ii) 240 s [1] (iii) decreases/reaction slower [1]

because concentration of thiosulfate decreases [1] frequency/chances/rate of collisions decreases [1] one mark can be scored for less/smaller amount/smaller volume of thiosulfate / less collisions

(b) rate increases with temperature (or at 42 °C) ORA [1]

particles/molecules/ions move faster or gain energy / ORA [1] (don’t accept reactants or atoms) more collisions / ORA [1] (last mark is for qualification of the collisions) i.e. greater frequency / more per unit time/more often /greater chance/more likely/more collision rate/more effective/more successful/more with activation energy / ORA [1]

4 One redox equation [1]

accept Fe2O3 + 3CO → 2Fe + 3CO2

2Fe2O3 + 3C → 4Fe + 3CO2

Fe2O3 + 3C → 2Fe + 3CO

C + O2 → CO2

CO2 + C → 2CO one acid/base equation [1]

CaO + SiO2 → CaSiO3

or CaCO3 + SiO2 → CaSiO3 + CO2 three more equations or comments [3] carbon burns to form carbon dioxide this reaction is exothermic or produces heat carbon dioxide is reduced to carbon monoxide carbon monoxide reduces hematite to iron carbon reduces hematite to iron limestone removes silica which is an impurity to form slag which is a waste product limestone decomposes or symbol/word equation




5 (a) Zn + H2SO4 → ZnSO4 + H2 / Zn + 2H+ → Zn2+ + H2 [2] marks are for correct reactants [1] correct products [1] If ionic equation is given don’t penalise SO4

2– spectator ions on both sides (b) (exothermic because) a cell produces (electrical) energy/electricity [1]

the next two marks score for electrons are lost AND gained / oxidation no. or state/valency both increases and decreases

/ two correct half equations i.e. Zn → Zn2+ + 2e– and 2H+ + 2e– → H2 [2] (c) zinc [1]

cond it is the more reactive metal / it supplies electrons / it forms ions more readily than iron [1]

(d) replace zinc with magnesium replace iron with copper use (more) concentrated sulfuric acid accept use a more concentrated acid / a more concentrated solution any two [2]




6 (a) (i) rate at which methanol formed by forward reaction [1] equals rate it is reacting in back reaction [1] rate of forward reaction equals rate of back reaction allow [1]

(ii) low/lower/decreased temperature [1]

high/higher/increased pressure [1] Explanations not needed but if they are given they must be correct IGNORE values of temperature and pressure

(iii) high pressure can be used / lower pressure due to expense or safety [1]

cannot use a low temperature as rate would be too slow the rate would not be economic [1]

(b) (i) ester [1] (ii) soap/sodium stearate or any acceptable salt/glycerol [1] (iii) burning both fuels forms carbon [1]

growing plants to make biodiesel removes carbon dioxide from atmosphere [1]

(c) (i) correct SF of an octane [1] (ii) add bromine (water)/bromine in an organic solvent [1]

result octane remains brown/orange/yellow/red [1] result octane goes colourless/decolourises [1] not clear/discolours colour of reagent must be shown somewhere for [3] otherwise max [2] accept equivalent test using KMnO4 in acid or alkali




7 (a) 3 bp and 1nbp around phosphorus [1] 1 bp and 3nbp around each chlorine [1]

(b) (i) PCl3 + 3H2O → 3HCl + H3PO3 [1] (ii) acid solutions same concentration [1]

measure pH/pH paper/Universal indicator [1] hydrochloric acid lower pH [1] colours of Universal indicator can be given as red<orange<yellow ignore precise pH values as long as HCl is lower than H3PO3 OR Acid solutions same concentration [1] add magnesium or any named metal above Hydrogen in reactivity series but not above magnesium calcium carbonate or any insoluble carbonate [1] hydrochloric acid react faster/shorter time [1] OR acid solutions same concentration [1] measure electrical conductivity [1] hydrochloric acid better conductor/bulb brighter [1] OR acid solutions same concentration [1] add sodium thiosulphate [1] hydrochloric acid forms precipitate faster/less time [1]

(iii) sodium hydroxide/sodium carbonate [1]

titration cond on correct reagent [1] second mark scores for mention of titration /burette/pipette/indicator. experimental detail not required any named soluble calcium salt e.g. calcium chloride/nitrate/hydroxide [1] precipitation/filter/decant/centrifuge [1]




8 (a) (i) (to avoid) carbon monoxide formation/so complete combustion occurs/avoid incomplete combustion So that CO2 is produced [1] CO does not dissolve/react with alkali [1]

(ii) CO2 is acidic [1] (iii) volume of gaseous hydrocarbon 20 cm3

volume of oxygen used = 90 cm3 [1] volume of carbon dioxide formed = 60 cm3 [1] no mark for 20 cm3 of hydrocarbon.

(iv) 2C3H6(g)/2CxHy(g) + 9O2(g) → 6CO2(g) + 6H2O(l) [1]

OR … C3H6(g) + 9/2O2(g) → 3CO2(g) + 3H2O(l) C3H6 [1] C3H6 can be given in the equation for the second mark

(b) (i) correct structural or displayed formula of another chlorobutane / dichlorobutane /

polychlorobutane [1] (ii) light / 200 °C / lead tetraethyl [1] (iii) cracking is the decomposition/breaking down of an alkane/hydrocarbon/petroleum [1]

heat/high temperature / Temperature between 450 °C to 800 °C OR catalyst / named catalyst [1] to give a simpler alkane and alkene [1] word equation or equation as example [1] to make polymers / to increase petrol fraction / organic chemicals/petrochemicals / hydrogen [1] any four





0620 CHEMISTRY








1 (i) Rb / Sr [1] (ii) I [1] (iii) Fe [1] (iv) P [1] (v) Si [1] 2 (a) (i) no reaction [1]

Fe + Sn2+ → Fe2+ + Sn / 2Fe + 3Sn2+ → 2Fe3+ + 3Sn [2] for realising that there would be a reaction shown by an attempt to write an equation e.g. writing Fe2Sn etc. allow [1] no reaction [1]

(ii) tin oxide, nitrogen dioxide (accept nitogen(IV) oxide/dinitrogen tetroxide), oxygen All three for two [2] accept correct formulae any two correct products [1] (b) (i) tin [1]

(ii) 4OH– → O2 + 2H2O + 4e– [2] not balanced allow [1] (iii) sulfuric acid [1] (c) zinc is more reactive than iron/steel [1]

tin is less reactive than iron/steel [1] zinc corrodes/reacts/loses electrons/is oxidised/is anodic/provides sacrificial protection/ forms positive ions (in preference to iron or steel) ORA allow iron is cathodic for this mark. [1] Iron/steel corrodes/reacts/rusts/loses electrons/is oxidised/is anodic/forms positive ions (in preference to tin). ORA allow tin is cathodic for this mark [1]




3 (a) (i) concentration of thiosulfate is proportional to volume of thiosulfate solution added (when total volume is same in all experiments) / concentration of acid always the same [2] for comments based on amount / to make experiments fair / comparable allow [1]

(ii) 240 s [1] (iii) decreases/reaction slower [1]

because concentration of thiosulfate decreases [1] frequency/chances/rate of collisions decreases [1] one mark can be scored for less/smaller amount/smaller volume of thiosulfate / less collisions

(b) rate increases with temperature (or at 42 °C) ORA [1]

particles/molecules/ions move faster or gain energy / ORA [1] (don’t accept reactants or atoms) more collisions / ORA [1] (last mark is for qualification of the collisions) i.e. greater frequency / more per unit time/more often /greater chance/more likely/more collision rate/more effective/more successful/more with activation energy / ORA [1]

4 One redox equation [1]

accept Fe2O3 + 3CO → 2Fe + 3CO2

2Fe2O3 + 3C → 4Fe + 3CO2

Fe2O3 + 3C → 2Fe + 3CO

C + O2 → CO2

CO2 + C → 2CO one acid/base equation [1]

CaO + SiO2 → CaSiO3

or CaCO3 + SiO2 → CaSiO3 + CO2 three more equations or comments [3] carbon burns to form carbon dioxide this reaction is exothermic or produces heat carbon dioxide is reduced to carbon monoxide carbon monoxide reduces hematite to iron carbon reduces hematite to iron limestone removes silica which is an impurity to form slag which is a waste product limestone decomposes or symbol/word equation




5 (a) Zn + H2SO4 → ZnSO4 + H2 / Zn + 2H+ → Zn2+ + H2 [2] marks are for correct reactants [1] correct products [1] If ionic equation is given don’t penalise SO4

2– spectator ions on both sides (b) (exothermic because) a cell produces (electrical) energy/electricity [1]

the next two marks score for electrons are lost AND gained / oxidation no. or state/valency both increases and decreases

/ two correct half equations i.e. Zn → Zn2+ + 2e– and 2H+ + 2e– → H2 [2] (c) zinc [1]

cond it is the more reactive metal / it supplies electrons / it forms ions more readily than iron [1]

(d) replace zinc with magnesium replace iron with copper use (more) concentrated sulfuric acid accept use a more concentrated acid / a more concentrated solution any two [2]




6 (a) (i) rate at which methanol formed by forward reaction [1] equals rate it is reacting in back reaction [1] rate of forward reaction equals rate of back reaction allow [1]

(ii) low/lower/decreased temperature [1]

high/higher/increased pressure [1] Explanations not needed but if they are given they must be correct IGNORE values of temperature and pressure

(iii) high pressure can be used / lower pressure due to expense or safety [1]

cannot use a low temperature as rate would be too slow the rate would not be economic [1]

(b) (i) ester [1] (ii) soap/sodium stearate or any acceptable salt/glycerol [1] (iii) burning both fuels forms carbon [1]

growing plants to make biodiesel removes carbon dioxide from atmosphere [1]

(c) (i) correct SF of an octane [1] (ii) add bromine (water)/bromine in an organic solvent [1]

result octane remains brown/orange/yellow/red [1] result octane goes colourless/decolourises [1] not clear/discolours colour of reagent must be shown somewhere for [3] otherwise max [2] accept equivalent test using KMnO4 in acid or alkali




7 (a) 3 bp and 1nbp around phosphorus [1] 1 bp and 3nbp around each chlorine [1]

(b) (i) PCl3 + 3H2O → 3HCl + H3PO3 [1] (ii) acid solutions same concentration [1]

measure pH/pH paper/Universal indicator [1] hydrochloric acid lower pH [1] colours of Universal indicator can be given as red<orange<yellow ignore precise pH values as long as HCl is lower than H3PO3 OR Acid solutions same concentration [1] add magnesium or any named metal above Hydrogen in reactivity series but not above magnesium calcium carbonate or any insoluble carbonate [1] hydrochloric acid react faster/shorter time [1] OR acid solutions same concentration [1] measure electrical conductivity [1] hydrochloric acid better conductor/bulb brighter [1] OR acid solutions same concentration [1] add sodium thiosulphate [1] hydrochloric acid forms precipitate faster/less time [1]

(iii) sodium hydroxide/sodium carbonate [1]

titration cond on correct reagent [1] second mark scores for mention of titration /burette/pipette/indicator. experimental detail not required any named soluble calcium salt e.g. calcium chloride/nitrate/hydroxide [1] precipitation/filter/decant/centrifuge [1]




8 (a) (i) (to avoid) carbon monoxide formation/so complete combustion occurs/avoid incomplete combustion So that CO2 is produced [1] CO does not dissolve/react with alkali [1]

(ii) CO2 is acidic [1] (iii) volume of gaseous hydrocarbon 20 cm3

volume of oxygen used = 90 cm3 [1] volume of carbon dioxide formed = 60 cm3 [1] no mark for 20 cm3 of hydrocarbon.

(iv) 2C3H6(g)/2CxHy(g) + 9O2(g) → 6CO2(g) + 6H2O(l) [1]

OR … C3H6(g) + 9/2O2(g) → 3CO2(g) + 3H2O(l) C3H6 [1] C3H6 can be given in the equation for the second mark

(b) (i) correct structural or displayed formula of another chlorobutane / dichlorobutane /

polychlorobutane [1] (ii) light / 200 °C / lead tetraethyl [1] (iii) cracking is the decomposition/breaking down of an alkane/hydrocarbon/petroleum [1]

heat/high temperature / Temperature between 450 °C to 800 °C OR catalyst / named catalyst [1] to give a simpler alkane and alkene [1] word equation or equation as example [1] to make polymers / to increase petrol fraction / organic chemicals/petrochemicals / hydrogen [1] any four





0620 CHEMISTRY








1 (a) Table of results for Experiment 1 initial and final volumes and differences completed correctly (1) to 1 decimal place (1) comparable to Supervisor’s report (1) ±4 cm3 [3] (b) Table of results for Experiment 2 initial and final volumes and differences completed correctly (1) to 1 decimal place (1) comparable to Supervisor’s report (1) ±4 cm3 [3] (c) bubbles/fizz/effervescence (1) glowing splint (1) relights/brighter (1) ignore reference to black [3] (d) oxygen/O2 (1) [1] (e) (i) colourless not clear to pink/purple (1) or reverse [1] (ii) potassium manganate is coloured/is an indicator/owtte (1) [1] allow not an acid/alkali reaction (f) (i) experiment 1 (1) [1] (ii) experiment 1 two times the volume of experiment 2 [1] (iii) solution B/potassium manganate more concentrated/stronger (1) or converse two times (1) two times as concentrated = 2 [2] (g) half the value of the result for experiment 2 (1) cm3 (1) half the volume of C used (1) [3] (h) advantage easy to use/quick/convenient/fairly accurate (1) disadvantage not accurate owtte (1) [2]




2 (a) (i) colourless (1) smell (1) [2] (ii) colourless/pale yellow and no smell (1) [1] (b) (i) catches fire/ignites (1) yellow/blue (1) yellow flame = 2 [2] (ii) extinguished/no reaction/owtte (1) [1] (c) (i) yellow/brown/orange/red (1) solution/dissolves (1) not ppt. [2] (ii) yellow/brown/orange (1) [1] (iii) two layers/rings (1) pink/purple top layer (1) [2] (d) (i) no reaction/no change/remains clear/stays same (1) [1] (ii) yellow (1) precipitate (1) [2] (e) brown/yellow/cream/white (1) precipitate (1) [2] (f) organic (1) alcohol/named alcohol/fuel (1) allow flammable [2]

(g) iodide/I– (1) not iodine [1] [Total: 40]





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1 (a) Table of results for Experiment 1 initial volume box, at time = 0 completed correctly (1) volume boxes correctly completed in ascending order (1) allow maximum of 2 consecutive identical numbers comparable to Supervisor’s results (1) ±15 at 180s [3] (b) Table of results for Experiment 2 initial volume box, at time = 0 completed correctly (1) volume boxes correctly completed in ascending order (1) allow maximum of 2 consecutive identical numbers comparable to Supervisor’s results (1) ±10 at 180s [3] (c) all points correctly plotted (3), –1 for any incorrect including t = 0 two smooth line graphs (2) lines clearly labelled (1) [6] (d) (i) experiment 1 (1) not ecf [1] (ii) acid X stronger/more concentrated or converse (1) allow ecf from (d)(i) [1] (e) reaction finished (1) note ‘reactants used up’ scores this mark all the acid used up (1) not all Mg used up [2] (f) value from graph (1) ± half small square (1.5s) tie line/indication shown (1) [2] (g) to prevent air being displaced into the measuring cylinder/owtte (1) causing inaccurate reading/volume measurement (1) [2] (h) advantage e.g. convenient/easy/quick to use/fairly accurate (1) disadvantage e.g. reference to inaccurate measurement (1) [2]




2 (a) white (1) [1] (b) any three from: pH paper turns blue/pH >7 (1) description of sublimate e.g. solid formed on sides of tube (1) reference to smell of the gas (1) description of condensate (1) max [3] (c) (i) white (1) precipitate (1) [2] (ii) paper turns blue/pH>7 (1) [1] (iii) no precipitate/no reaction/no change/colourless/stays clear (1) [1] (d) effervescence/bubbles/fizz (1) limewater (1) milky/cloudy (1) [3] (e) (i) white (1) precipitate (1) [2] (ii) no/thin/slight precipitate/no reaction (1) [1] (f) ammonium (1) chloride (1) [2] (g) calcium (1) carbonate (1) [2] [Total: 40]





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1 (a) beaker (1) [1] (b) (i) (arrow) labelled heat in correct position under shaded crystals (1) (ii) arrow labelled water in test-tube at or below the level of the ice (1) [2] (c) to cool/condense the water or steam/owtte (1) [1] (d) physical test ignore chemical tests boiling point/freezing point (1) 100/0°C (1) [2] 2 (a) any two variables max 2

• volume

• concentration of acid allow amount

• volume of sodium thiosulfate/total volume of solution

• temperature

• printed sheet

• same size flask ignore reference to pressure/catalyst/surface area/light max [2] (b) straight line drawn with a ruler, missing anomalous point but touching all other points (1) not multiple lines [1] (c) any two sensible errors that could be from same category max 2

• qualified measurement error e.g. volume

• qualified timing error

• recording error

• plotting error

• temperature variation

• contamination from previous experiment not systematic error max [2] (d) 0.056–0.064 range (1) indication on graph (1) [2] (e) more particles/particles closer together (1) more collisions (1) [2] (f) sketch straight line to the LEFT of the original (1) [1]




3 (a) chromatography (1) [1] (b) water (1) [1] (c) origin/base line/datum (1) [1] ignore references to start/initial/pencil (d) sweet C has 4 colours (1) sweet D has 3 colours (1) allow C has one more colour/more colours than D for one mark 2 colours are the same (1) [3] 4 Experiment 1 (a) and (b) initial and final volumes completed correctly (1) 0.0, 32.0 Experiment 2 initial and final volumes completed correctly (1) 19.0, 35.0 all readings in both experiments to 1 decimal place (1) both differences correctly calculated (1) [4] (c) oxygen(1) [1] (d) (i) colourless not clear to purple/pink (1) or reverse [1] (ii) potassium manganate is coloured/owtte (1) [1] accept is not an acid/alkali reaction (e) (i) experiment 1(1) allow ecf [1] (ii) experiment 1 2× volume of experiment 2 [1] (iii) solution B more concentrated/stronger (1) or converse 2× as concentrated (2) [2] (f) half value from table result for experiment 2 / 8 (1) cm3 (1) half volume of peroxide used (1) [3] (g) advantage easy to use/quick/convenient/fairly accurate (1) disadvantage not accurate owtte (1) [2]




5 (a) (ii) colourless (1) allow yellow no smell (1) [2] (b) (ii) extinguished/owtte (1) [1] (d) yellow (1) precipitate (1) [2] (e) organic (1) allow hydrocarbon fuel/alcohol/named alcohol (1) allow flammable [2] 6 (a) diagram of a filter paper in a funnel (1) label funnel/filter paper (1) [2] (b) 0.45, 0.95, 1.40, 1.90, 2.35 and 2.35 (2), –1 for each incorrect up to 2 [2] (c) all points plotted correctly (2), –1 for each incorrect point up to 2 two intersecting straight lines (1) ignore origin [3] (d) 5 cm3 (1) ignore unit [1] 7 (a) appropriate test (1) result (1) [2] e.g. pH paper or named indicator 11–14 or correct colour named metal salt solution/ion correct colour precipitate ammonium salt/heat ammonia/owtte (b) fizzy drinks may be acidic/contain carbon dioxide (1) chlorine formed (1) toxic (1) max [2] (c) answer connected to health and safety (1) [1] allow to affect the environment/to clean it (d) litmus/pH/UI paper (1) bleached owtte (1) [2] [Total: 60]





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1 (a) measuring cylinder (1) [1] (b) (i) condenser (1) accept condensing tube evaporating dish/basin/bowl (1) accept crystallising dish/basin/bowl tripod (1) [3] (ii) A/distillation (1) [1] (c) ignore reference to filtering heat/evaporate/use apparatus B (1) not ‘heat’ if the method would not work to crystallising point/until saturated (1) [2] 2 (a) Table of results highest temperatures correct (3), –1 for each incorrect up to 3 26, 28, 34, 38, 42 ignore decimal place unless incorrect temperature rises (1) 4, 6, 12, 16, 20 ignore decimal place unless incorrect [4] (b) points plotted correctly (2), –1 for each incorrect up to 2 ignore origin straight line drawn with a ruler and missing anomalous point (1) need not go through origin, do not accept double lines [3] (c) second point/Experiment 2/0.6 g zinc/6 °C (1) [1] (d) 24 (1) accept 23.5–24.5 °C (1) extrapolation shown on grid (1) [3] (e) blue colour turns colourless/paler/owtte (1) not just colour changes pink/red/brown/black solid (1) not Zn dissolves/Cu forms fizzing/bubbles (1) not gas given off max [2] 3 (a) lamp lights (1) fizzing/bubbles/green gas (1) ignore gas/H2 produced allow bleach like smell [2] (b) carbon/graphite/platinum (1) [1] (c) hydrogen/H2 (1) not H [1] (d) fume cupboard/ventilated area (1) protective clothing e.g. gloves/goggles/lab coat/tie back hair (1) [2]




4 Experiment 1 (a) Table of results volume boxes completed correctly (3), –1 for each incorrect up to 3 0, 13, 22, 30, 36, 43, 49 ignore decimal place unless incorrect [3]

(b) Experiment 2 volume boxes completed correctly (3), –1 for each incorrect up to 3 0, 5, 10, 13, 17, 20, 23 ignore decimal place unless incorrect [3]

(c) all points correctly plotted (3), –1 for any incorrect up to 3 two smooth line graphs and must go through origin (2) lines clearly labelled (1) [6]

(d) (i) Experiment 1/acid X (1) [1] (ii) acid X stronger/more concentrated or converse (1) allow 2× ignore reference to catalyst/reactivity [1]

(e) reaction finished (1) all acid used up (1) not Mg used up, ignore reactants used up [2]

(f) value from graph (1) 69–72 s allow ecf from incorrect graph tie line/indication shown (1) [2]

(g) advantage e.g. convenient/easy/quick to use/fairly accurate (1) disadvantage e.g. reference to inaccurate measurement (1) do not allow 2 marks for references to accuracy [2]

5 (b) (i) white (1) precipitate (1) [2] (ii) paper turns blue (1) pH>7 (1) smelly/pungent gas (1) max [2] (iii) no precipitate/reaction/change (1) [1]

(e) carbon dioxide/CO2 produced (1) [1]

(f) calcium (1) carbonate (1) [2]

6 known/fixed/same volume/same mass of water (1) temperature taken at beginning and end or temperature change (1) known mass/volume/change in mass of fuel (1) accept any measurement of mass of fuel ignite/burn the fuel or heat the water (1) accept flame in diagram both fuels tested (1) comparison (1) accept any attempt at comparison

[Total: 60]





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1 (a) measuring cylinder (1) [1] (b) (i) condenser (1) accept condensing tube evaporating dish/basin/bowl (1) accept crystallising dish/basin/bowl tripod (1) [3] (ii) A/distillation (1) [1] (c) ignore reference to filtering heat/evaporate/use apparatus B (1) not ‘heat’ if the method would not work to crystallising point/until saturated (1) [2] 2 (a) Table of results highest temperatures correct (3), –1 for each incorrect up to 3 26, 28, 34, 38, 42 ignore decimal place unless incorrect temperature rises (1) 4, 6, 12, 16, 20 ignore decimal place unless incorrect [4] (b) points plotted correctly (2), –1 for each incorrect up to 2 ignore origin straight line drawn with a ruler and missing anomalous point (1) need not go through origin, do not accept double lines [3] (c) second point/Experiment 2/0.6 g zinc/6 °C (1) [1] (d) 24 (1) accept 23.5–24.5 °C (1) extrapolation shown on grid (1) [3] (e) blue colour turns colourless/paler/owtte (1) not just colour changes pink/red/brown/black solid (1) not Zn dissolves/Cu forms fizzing/bubbles (1) not gas given off max [2] 3 (a) lamp lights (1) fizzing/bubbles/green gas (1) ignore gas/H2 produced allow bleach like smell [2] (b) carbon/graphite/platinum (1) [1] (c) hydrogen/H2 (1) not H [1] (d) fume cupboard/ventilated area (1) protective clothing e.g. gloves/goggles/lab coat/tie back hair (1) [2]




4 Experiment 1 (a) Table of results volume boxes completed correctly (3), –1 for each incorrect up to 3 0, 13, 22, 30, 36, 43, 49 ignore decimal place unless incorrect [3]

(b) Experiment 2 volume boxes completed correctly (3), –1 for each incorrect up to 3 0, 5, 10, 13, 17, 20, 23 ignore decimal place unless incorrect [3]

(c) all points correctly plotted (3), –1 for any incorrect up to 3 two smooth line graphs and must go through origin (2) lines clearly labelled (1) [6]

(d) (i) Experiment 1/acid X (1) [1] (ii) acid X stronger/more concentrated or converse (1) allow 2× ignore reference to catalyst/reactivity [1]

(e) reaction finished (1) all acid used up (1) not Mg used up, ignore reactants used up [2]

(f) value from graph (1) 69–72 s allow ecf from incorrect graph tie line/indication shown (1) [2]

(g) advantage e.g. convenient/easy/quick to use/fairly accurate (1) disadvantage e.g. reference to inaccurate measurement (1) do not allow 2 marks for references to accuracy [2]

5 (b) (i) white (1) precipitate (1) [2] (ii) paper turns blue (1) pH>7 (1) smelly/pungent gas (1) max [2] (iii) no precipitate/reaction/change (1) [1]

(e) carbon dioxide/CO2 produced (1) [1]

(f) calcium (1) carbonate (1) [2]

6 known/fixed/same volume/same mass of water (1) temperature taken at beginning and end or temperature change (1) known mass/volume/change in mass of fuel (1) accept any measurement of mass of fuel ignite/burn the fuel or heat the water (1) accept flame in diagram both fuels tested (1) comparison (1) accept any attempt at comparison

[Total: 60]





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Question Number

Key Question Number

Key

1 C 21 A

2 D 22 C

3 D 23 C

4 B 24 B

5 C 25 A

6 D 26 B

7 B 27 B

8 B 28 C

9 C 29 D

10 B 30 C

11 C 31 A

12 C 32 D

13 A 33 A

14 D 34 C

15 A 35 C

16 B 36 A

17 D 37 B

18 C 38 A

19 D 39 C

20 B 40 D





0620 CHEMISTRY








Question Number

Key Question Number

Key

1 C 21 A

2 D 22 C

3 D 23 B

4 B 24 A

5 C 25 C

6 C 26 A

7 B 27 B

8 B 28 D

9 B 29 A

10 D 30 A

11 D 31 C

12 A 32 D

13 C 33 A

14 C 34 A

15 D 35 C

16 C 36 A

17 C 37 C

18 B 38 B

19 C 39 D

20 B 40 D





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Question Number

Key Question Number

Key

1 C 21 B

2 D 22 B

3 D 23 C

4 B 24 A

5 B 25 B

6 C 26 C

7 D 27 C

8 C 28 B

9 B 29 D

10 B 30 C

11 A 31 A

12 C 32 A

13 C 33 C

14 A 34 D

15 D 35 C

16 C 36 B

17 B 37 A

18 D 38 A

19 A 39 D

20 D 40 C





0620 CHEMISTRY









1 (a) A: thermometer; [1] B: beaker; [1]

(b) (i) idea that heat is evenly distributed e.g.

to make sure that temperature (of water) is the same throughout / the heat gets to the (stearic) acid at steady rate / the heart gets to test tube at a constant rate / to make sure the water is at an even temperature (throughout) / so not just hot at the bottom / so that hot parts of the water mix with cold; [1]

(ii) anhydrous / white copper sulfate; [1]

turns blue; [1] or anhydrous / blue cobalt chloride; turns pink / turns red; allow: second mark if copper sulfate or cobalt chloride given without reference to colour or anhydrous

(c) (i) 48(°C); [1] (ii) 72(°C); [1] (d) arrangement: close together / touching / irregular / random; [1]

motion: sliding over each other / moving slowly; [1] allow: irregular / random allow: move faster than solid but slower than gas

(e) (i) the melting point is different / 3rd box down ticked; [1] (ii) any suitable: e.g.

food / medicines / drugs / named food / medicine / cosmetics / drinking water / water for cooking / water for washing; [1] allow: relevant places or processes where purity of substances is important e.g. drinking / eating / cooking / surgeries / hospitals / kitchen

[Total: 11] 2 (a) (i) B; [1]

allow: sulfur / S8 / S (ii) a substance containing only one type of atom; [1]

allow: a substance with the same type of atoms / a substance containing the same atoms / a substance that cannot be broken down (by chemical means)

(b) 64 [1] (c) Na2S [1]




(d) D; [1] ions can move / ions are free; [1]

note: second mark dependent on first mark being correct

(e) oxidation; [1]

[Total: 7]

3 (a) pH 3; [1]

(b) dip (litmus) paper in the solution / acid or add litmus solution to the acid / add acid to litmus paper; [1]

note: if another substance added e.g. add a metal or a further process e.g. boil the solution, the first mark is lost but the next two marks can still be obtained.

blue litmus; [1]

turns red / pink; [1] reject: litmus bleaches

note: if the indicator is incorrect, the second two marks cannot be obtained.

(c) (i) calcium carbonate + hydrochloric acid → calcium chloride + carbon dioxide + water [3] note: –1 per error

(ii) extraction of iron / making cement / making lime / neutralising acidic lakes / (flue gas) desulfurisation / making glass / neutralising acidic waste / any other suitable use; [1]

(iii) calcium oxide; [1] allow: calcium hydroxide / lime / milk of lime / other carbonates allow: correct formulae

(d) H2 (on right); [1] correct balance (i.e. 2 on left); [1]

(e) (i) molecular formula of ethanoic acid is C2H4O2; [1] full structural formula of ethanol is: [1]

H H │ │ H ― C — C — O — H │ │ H H

allow: OH in place of O- H

(ii) C2H4 + H2O; [1]

[Total: 14]




4 (a) bitumen → surfacing roads; [1] lubricating fraction → waxes and polishes; [1] refinery gases → heating; making chemicals [1] allow: refinery gas → making chemicals naphtha → making chemicals; [1]

(b) substance containing hydrogen and carbon only; [1] (c) (i) H [1]

│ H — C — H │ H

(ii) CO2 (on right); [1]

correct balance (i.e. 2 on left) [1] note: balance mark dependent on CO2 on right

(iii) any two of: [2]

family of similar (organic) compounds / with similar chemical properties / presence of same functional group / same general formula / allow: compounds with a trend in physical properties allow: difference of CH2 between one member and another

(iv) ethane; [1] [Total: 11]




5 (a) lower the test tube (into the HCl) / mix the reactants / mix the zinc and hydrochloric acid; [1] (b) (i) all points plotted correctly including the 0-0 point; [2]

note: –1 per error curve of best fit drawn; [1]

(ii) because the reaction has finished / reaction has stopped / reaction is complete; [1]

the hydrochloric acid has been used up / hydrochloric acid is limiting / the limiting reagent has been used up; [1] reject: the zinc has been used up / the zinc and hydrochloric acid have been used up

(c) concentration; increases; decreases; speed; (1 mark each) [4] (d) filter (off excess zinc) / decant (off solution); [1]

note: if no filtration or decantation no further marks can be scored heat filtrate to crystallisation point / evaporate some of the water / heat for a little while / leave filtrate in a warm place / leave on the windowsill; [1] dry crystals with filter paper; [1] allow: dry in oven below 100°C

[Total: 13] 6 (a) (i) lithium + water → lithium hydroxide + hydrogen [2]

note: –1 per error (ii) 2Na + 2H2O → 2NaOH + H2 [1]

allow: equations doubling or halving all species




(b) 2 marks for order of reactivity: • order of reactivity is potassium > sodium > lithium / implication of rate of bubble

formation or some other observation clearly shows the order is potassium > sodium > lithium; [2]

note: reactivity increases down group / only two of the elements are named but they are in correct order of reactivity e.g. potassium is more reactive than sodium = 1 mark 3 marks for observations: [3] any 3 of: • float on surface (with any of the 3 elements) • bubbles given off / effervescence (with any of the 3 elements) • fizzes / sound heard (with any of the 3 elements) • Na / K go into a ball OR Na / K melt ignore: Li goes into ball or melts allow: they go into a ball • move across the surface of the water) (with any of the 3 elements) • K (bursts into) flame • lilac / violet flame for K allow: Na (bursts into) flame / yellow flame • Na / K spits / explodes (when gets very small) allow: pops or sparks (for Na or K) • Li / Na / K disappears / gets smaller

(c) (i) anode: E; [1]

electrolyte: A; [1] (ii) + electrode: chlorine / Cl2; [1]

– electrode: sodium / Na; [1] reject: ions / chloride

(iii) graphite; [1] (d) any two of: [2]

• shiny (when cut) • conduct heat • conduct electricity • malleable / soft / easy to cut • ductile

[Total: 15] 7 (a) (i) sulfur + oxygen → sulfur dioxide [2]

(sulfur + oxygen → sulfur oxide / sulfur trioxide) = 1 mark (ii) SO2 oxidised to SO3 / 1st box ticked; [1]

O3 reduced to O2 / 3rd box ticked; [1] (iii) H2O; [1]




(b) any 3 of; [3] • (sulfuric acid) reacts (with calcium carbonate) • neutralisation (reaction) • gas released / CO2 released • soluble substances formed (on reaction) • buildings eroded / (surface) crumbled / damaged / pitted / note: a correct word or symbol equation = 2 marks note: neutralisation reaction = 2 marks

(c) kills (or harms) organisms in lakes / forest death / deforestation / kills trees / kills plants /

damages plants / irritation of throat or lungs / reference to asthma; [1] allow: kills (or harms) animals or fish in lakes or rivers / kills corals. allow: leaches soil minerals allow: leaf burn ignore: kills animals / fish in the sea / kills fish unqualified ignore: acidifies soil / acidifies lakes ignore: wears away / erodes carbonate rocks / erodes soil ignore: destroys plants / animals

[Total: 9]





0620 CHEMISTRY









1 (a) carbon dioxide → turns limewater milky; [1] chlorine → bleaches damp litmus paper; [1] oxygen → relights a glowing splint; [1] hydrogen → pops with a lighted splint; [1] (b) (i) manganese(IV) oxide + hydrochloric acid → manganese chloride + chlorine + water [3] note: –1 mark per error allow: manganese oxide (on left) ignore: incorrect oxidation numbers of manganese chloride (ii) C [1] (c) (i) O2 (on left); [1] correct balance dependent on O2 or 2O on left i.e. 2 (on right); [1] (ii) hydrogen: for fuel / as a reducing agent / any other specific use e.g. manufacture of margarine, making ammonia [1] water: any suitable use e.g. coolant / washing / cooking / drinking etc. [1] [Total: 12] 2 (a) sodium hydroxide solution; [1] (b) any pH above 7; [1] (c) any two of: [2] place indicator into solution; universal indicator paper or solution / pH meter; compare colour with pH colour chart / take reading on pH meter; (d) (i) plants might die / to allow good crop growth / good growth of grass etc. [1] (ii) any two of: [2] calcium carbonate is a base; reacts (with acids); neutralises (the acid); [Total: 7] 3 (a) (i) chlorine: (light) green; [1] not: yellow bromine: brown / red / red-brown; [1] (ii) chlorine: the boiling point is below / less than / lower than room temperature; [1] bromine: the melting point is below / less than / lower than room temperature and the

boiling point is above / higher than room temperature: [1] (iii) any value between +190 °C to 450 °C [1]




(b) (i) I2 (on the right) [1] correct balance i.e. 2 on left (if I2 or 2I on right) [1] (ii) potassium chloride; iodine; [2] (iii) 3 [1] (c) nitric; silver; yellow; precipitate; [4] [Total: 14] 4 (a) (i) B; [1] (ii) C; [1] (iii) D; [1] (b) lightning activity / car engines / high temperature furnaces; [1] (c) irritation of nose / asthma / acid rain (or named effect of acid rain) [1] (d) 46; [1] (e) (i) CO / carbon monoxide; [1] gains oxygen; [1] allow: oxidation number of carbon increases / loss of electrons (ii) substance which speeds up a reaction / increases reaction rate; [1] (iii) amount of oxygen reduced; [1] so incomplete combustion occurs / the carbon is not fully oxidised; [1] (iv) CO is poisonous / toxic; [1] allow: higher level answers e.g. combining with haemoglobin / haem [Total: 12] 5 (a) any three of: hard / high density / high melting (or boiling) points; allow: forms coloured compounds / general metallic properties [3] (b) (i) iron + sulfuric acid → iron sulfate + hydrogen [2] note: –1 per error




(ii) suitable apparatus for measuring gas volume e.g. syringe / upturned measuring cylinder; [1] closed system; [1] measure volume of gas; [1] at given time intervals; [1] ALLOW: (for max 3 marks) unstoppered flask on top of balance (1) measure decrease in mass of flask (1) at given time intervals (1) (c) (i) exothermic; [1] (ii) two (or more) different atoms / elements bonded / joined together; [1] note: both atoms / elements and bonded / joined needed (iii) FeS; [1] [Total: 12] 6 (a) X drawn in bottom compartment or in tube leading from arrow showing petroleum in; [1] (b) naphtha [1] (c) kerosene: jet fuel / fuel for heating / cooking fuel / kerosene lamps; [1] diesel: fuel for lorries / cars / tractors; [1] (d) mixture; heated; lower; condenses; boiling; [5] (e) (i) B and D; [1] (ii) B and D [2] [Total: 12] 7 (a) any 4 of: in solid salt the particles can’t move / fixed; salt dissolves / dissolving; (because) forces between particles / ions (in solid) are overcome; diffusion; salt particles in solution move; randomly; water particles moving; water and salt particles (constantly) colliding; salt particles spread themselves out or mix with water; [4] (b) (i) a sodium atom loses its outermost electron and a chlorine atom gains an electron / 2nd

box down ticked; [1]




(ii) in solid sodium chloride, the ions can’t move / fixed; [1] in molten sodium chloride the ions can move / free; [1] (iii) positive electrode: chlorine; [1] negative electrode: hydrogen; [1] (iv) cathode; [1] (v) conducts electricity; [1] allow: non-reactive / inert; [Total: 11]





0620 CHEMISTRY









1 (a) carbon dioxide → turns limewater milky; [1] chlorine → bleaches damp litmus paper; [1] oxygen → relights a glowing splint; [1] hydrogen → pops with a lighted splint; [1] (b) (i) manganese(IV) oxide + hydrochloric acid → manganese chloride + chlorine + water [3] note: –1 mark per error allow: manganese oxide (on left) ignore: incorrect oxidation numbers of manganese chloride (ii) C [1] (c) (i) O2 (on left); [1] correct balance dependent on O2 or 2O on left i.e. 2 (on right); [1] (ii) hydrogen: for fuel / as a reducing agent / any other specific use e.g. manufacture of margarine, making ammonia [1] water: any suitable use e.g. coolant / washing / cooking / drinking etc. [1] [Total: 12] 2 (a) sodium hydroxide solution; [1] (b) any pH above 7; [1] (c) any two of: [2] place indicator into solution; universal indicator paper or solution / pH meter; compare colour with pH colour chart / take reading on pH meter; (d) (i) plants might die / to allow good crop growth / good growth of grass etc. [1] (ii) any two of: [2] calcium carbonate is a base; reacts (with acids); neutralises (the acid); [Total: 7] 3 (a) (i) chlorine: (light) green; [1] not: yellow bromine: brown / red / red-brown; [1] (ii) chlorine: the boiling point is below / less than / lower than room temperature; [1] bromine: the melting point is below / less than / lower than room temperature and the

boiling point is above / higher than room temperature: [1] (iii) any value between +190 °C to 450 °C [1]




(b) (i) I2 (on the right) [1] correct balance i.e. 2 on left (if I2 or 2I on right) [1] (ii) potassium chloride; iodine; [2] (iii) 3 [1] (c) nitric; silver; yellow; precipitate; [4] [Total: 14] 4 (a) (i) B; [1] (ii) C; [1] (iii) D; [1] (b) lightning activity / car engines / high temperature furnaces; [1] (c) irritation of nose / asthma / acid rain (or named effect of acid rain) [1] (d) 46; [1] (e) (i) CO / carbon monoxide; [1] gains oxygen; [1] allow: oxidation number of carbon increases / loss of electrons (ii) substance which speeds up a reaction / increases reaction rate; [1] (iii) amount of oxygen reduced; [1] so incomplete combustion occurs / the carbon is not fully oxidised; [1] (iv) CO is poisonous / toxic; [1] allow: higher level answers e.g. combining with haemoglobin / haem [Total: 12] 5 (a) any three of: hard / high density / high melting (or boiling) points; allow: forms coloured compounds / general metallic properties [3] (b) (i) iron + sulfuric acid → iron sulfate + hydrogen [2] note: –1 per error




(ii) suitable apparatus for measuring gas volume e.g. syringe / upturned measuring cylinder; [1] closed system; [1] measure volume of gas; [1] at given time intervals; [1] ALLOW: (for max 3 marks) unstoppered flask on top of balance (1) measure decrease in mass of flask (1) at given time intervals (1) (c) (i) exothermic; [1] (ii) two (or more) different atoms / elements bonded / joined together; [1] note: both atoms / elements and bonded / joined needed (iii) FeS; [1] [Total: 12] 6 (a) X drawn in bottom compartment or in tube leading from arrow showing petroleum in; [1] (b) naphtha [1] (c) kerosene: jet fuel / fuel for heating / cooking fuel / kerosene lamps; [1] diesel: fuel for lorries / cars / tractors; [1] (d) mixture; heated; lower; condenses; boiling; [5] (e) (i) B and D; [1] (ii) B and D [2] [Total: 12] 7 (a) any 4 of: in solid salt the particles can’t move / fixed; salt dissolves / dissolving; (because) forces between particles / ions (in solid) are overcome; diffusion; salt particles in solution move; randomly; water particles moving; water and salt particles (constantly) colliding; salt particles spread themselves out or mix with water; [4] (b) (i) a sodium atom loses its outermost electron and a chlorine atom gains an electron / 2nd

box down ticked; [1]




(ii) in solid sodium chloride, the ions can’t move / fixed; [1] in molten sodium chloride the ions can move / free; [1] (iii) positive electrode: chlorine; [1] negative electrode: hydrogen; [1] (iv) cathode; [1] (v) conducts electricity; [1] allow: non-reactive / inert; [Total: 11]





0620 CHEMISTRY









1 (a) (i) evaporation / boiling / vaporisation / evaporate / vaporise; [1] condensation / liquefaction / condense / liquefy; [1] (ii) condensation accept: correct equation H2O(g)→H2O(l)

because energy / heat is given out / gas has more energy than liquid / need to supply energy to change liquid to gas so reverse must give out energy / bonds form; [1]

(b) chlorination / chlorine to kill microbes; [1]

filtration or filter; [1] accept: sedimentation or sand or gravel or grit

(c) (i) combustion of fossil fuels; [1]

(which contain) sulfur; [1] sulfur dioxide formed; [1] (reacts in air / with water to form) sulfurous / sulfuric acid; [1] OR nitrogen and oxygen in air; [1] react at high temperatures / in engines; [1] to form oxides of nitrogen or named oxide of nitrogen; [1] (reacts in air / with water to form) nitrous / nitric acid; [1] [max 4]

(ii) calcium oxide is soluble in water / reacts with water to form

calcium hydroxide; [1] pH above 7 / the water becomes alkaline; [1] OR calcium carbonate insoluble in water; [1] pH cannot be above 7 / water is neutral / does not make water alkaline; [1] [max 2] [Total: 11] 2 (a) nitric acid; [1]

sodium hydroxide / carbonate / hydrogen carbonate; [1]

copper(II) oxide / hydroxide / carbonate; [1] any named soluble chloride; [1] accept: hydrochloric acid / hydrogen chloride silver(I) nitrate / ethanoate / sulfate; [1] must be soluble silver salt not silver oxide / carbonate

zinc(II) sulfate [1]

(b) (i) Ag+(aq) + Cl –(aq) → AgCl(s) [2]

equation correct state symbols missing [1]

(ii) ZnCO3 + H2SO4 → ZnSO4 + CO2 + H2O [2] correct formula for zinc sulfate = 1

[Total: 10]




3 (a) (i) decrease down group; [1] (ii) caesium / francium; [1] (iii) 2Rb + 2H2O → 2RbOH + H2 [2] not balanced = [1] (b) (i) Li+ [1] (ii) N3– [1] (iii) regular arrangement of ions / particles / positive and negative ions alternate; [1]

not: atoms (iv) 3:1; [1] ratio to balance charges / reason in terms of valency; [1] [Total: 9] 4 (a) 2 + 8 + 11 + 2 [1] (b) hard;

strong / high tensile strength; high mp / bp / high fixed points; high density; [2]

three properties = [2] two properties = [1] not: properties of all metals e.g. good conductor, lustre etc. or form coloured compounds

(c) catalyst would not affect yield / change position of equilibrium / affects both sides equally; [1]

(higher) temperature would reduce yield / increase in temperature would favour back reaction; [1]

(d) (i) V3+ is oxidant; [1] (ii) V3+ to V4+; [1]

increase in oxidation number / electron loss; [1] [Total: 8]

5 (a) calcium carbonate → calcium oxide + carbon dioxide [1] accept: correct symbol equation

Ca(OH)2 → CaO + H2O [1]

(b) (i) CuO and NO2 and O2; [1]

accept: names or correct formulae




(ii) 2NaNO3 → 2NaNO2 + O2 [2] accept: NaNO3 → NaNO2 + 1/2 O2 not balanced = [1]

(c) Na / Ca; [1] (d) Cu; Ag; [2]

accept: ions Cu2+ and Ag+ [Total: 8] 6 (a) 10 cm3; [1] 65 cm3; [1] (b) (i) chlorination / substitution / photochemical / exothermic / halogenation / free radical; [1] (ii) (compounds) same molecular formula; different structural formulae; [2] (iii) CH3–CH2–CH2–CH2–Cl [1]

CH3–CH2–CH(Cl)–CH3 [1] (c) (i) potassium manganate(VII) / potassium dichromate(VI) / copper(II) oxide; [1] note: do not insist on oxidation numbers but if given must be correct (ii) butanoic acid; [1] (iii) butyl ethanoate; [1] correct formula all bonds shown = [2] if alkyl groups incorrect then correct ester linkage showing bonds = [1] [2] [Total: 12]




7 (a) burning produces toxic gases / harmful to health increases greenhouse gases / global warming reduces visual pollution / litter reduces risks to wildlife shortage of landfill sites / reduces space needed in landfill sites / saves space non-biodegradable / long time to rot / decompose / accumulates waste burning source of energy / used to generate electricity

recycling conserves petroleum / natural resources difficult to recycle / expensive / takes much energy problems over sorting reduces need for landfill quality of plastic is reduced each time it is recycled four DIFFERENT valid points which are advantages or disadvantages of burning and/or recycling [4]

(b) (i) addition (polymerisation); [1]

(polymer) only product / no by-products; [1] condensation (polymerisation); [1]

(polymer and) simple molecule / water / hydrogen chloride / one other product forms; [1]

(ii) a correct linkage (for a polyamide / polyester); [1] two different monomers; [1] [Total: 10] 8 (a) (i) device which changes chemical energy; [1] into electrical energy; [1] OR produces a voltage / potential difference / electricity; [1] due to difference in reactivity of two metals; [1]

OR produces a voltage / potential difference / electricity; [1] by redox reactions; [1] (ii) negative / electrode B / right electrode; [1]

accept: anode because it is the electrode which supplies electrons to external circuit loses ions / iron ions / Fe2+ or Fe3+; [1] electrons move from this electrode; [1]

(iii) change of mass of electrode / mass of rust formed; [1] time / mention of stop watch / regular intervals; [1] (iv) to make it a better conductor; [1]




(b) moles of Fe = 51.85/56 = 0.926 (0.93); [1] moles of O = 22.22/16 = 1.389 (1.39); [1] moles of H2O = 16.67/18 = 0.926 (0.93); [1]

if given as 0.9 1.4 0.9 three of the above correct = [2] two of the above correct = [1] simplest whole number mole ratio Fe : O : H2O is 2: 3: 2 / Fe2O3.2H2O; [1] allow: ecf for a formula based on an incorrect whole number ratio [Total: 12]





0620 CHEMISTRY









1 (a) neon has full outer shell / energy level / valency shell / octet / 8 (electrons) in outer shell / neon does not need to lose or gain electrons; [1] fluorine atoms have 7 electrons / needs 1 to fill / has incomplete shell / forms bonds with other fluorine atoms / fluorine (atoms) form covalent bonds / shares electrons; [1]

(b) atomic number / proton number / number of protons (in one atom); [1] (c) weak intermolecular (or between molecules) forces / Van der Waals forces between

molecules / low amount of energy required to break bonds between molecules; [1] strong bonds don’t break / covalent bonds don’t break / (unnamed) bonds within molecules / between atoms don’t break; [1]

(d) 1 non-bonding pair on each nitrogen atom; [1]

6 electrons between nitrogen atoms; [1] 2 (a) weak forces between layers or between (hexagonal) rings / weak bonds between layers or

between (hexagonal) rings / Van der Waals forces between layers or between (hexagonal) rings; [1] (layers/rings) slip/slide (over each other) / move over each other [1]

(b) strong bonds (between atoms) / covalent bonds (between atoms); [1]

all bonds are covalent/strong / each atom covalently bonded / carbon (atoms) is bonded to four others / bonds are directional / (atoms are arranged) tetrahedrally; [1]

accept: carbon has four bonds (c) graphite has delocalised / mobile / free electrons; [1]

diamond (outer shell) electrons used / fixed / localised in bonding / no delocalised electrons / no mobile electrons / no free electrons; [1]

3 (a) flexible / easily form different shapes / easily moulded / bends (without cracking); [1]

non-biodegradable / unreactive / don’t corrode / prevent corrosion / prevent oxidation (of the conducting metal) / water resistant / waterproof; [1]

(b) improve appearance / decorative / makes appearance shiny; [1]

prevent corrosion / rusting / protect steel / chromium will not corrode / chromium is not oxidised / chromium protected by an oxide layer; [1]

(c) low density / light / protected by oxide layer / no need to paint / resists corrosion / (high)

strength / strong;; any two [2] note: high strength to weight ratio = 2

(d) high mpt / withstands high temperature / good conductor (of heat) / heats up quickly /

malleable / ductile / resists corrosion / good appearance / unreactive (or example of lack of reactivity e.g. does not react with food or water or acid or air);; any two [1]




(e) (lattice) positive ions / cations / metal ions and sea of electrons / delocalised or free or mobile or moving electrons; [1] attraction between positive ions and electrons; [1]

4 (a) (i) oxygen; [1]

carbon dioxide / fluorine / carbon monoxide; [1] (ii) decrease mpt (of alumina/Al2O3) / lower (operating) temperature (from 1900/2100 (°C) to

800/1000 (°C) / reduce energy (accept heat or electrical) requirement; [1] improve conductivity / dissolves the Al2O3 / acts as solvent; (allow: makes aluminium oxide conduct / to conduct electricity / making ions free to move) [1]

(iii) Al2O3 (accept alumina) reacts / dissolves / forms a salt and water / is neutralised; [1]

(Fe2O3 removed by) filtration / centrifugation / decantation; [1] (b) (i) electrolysis / electrolyte / electrodes / anode / cathode / electricity / cell; [1]

chlorine formed at anode (positive electrode); (note: can be awarded from a correct or incorrect equation with Cl2 as the only substance on the right as long as anode is mentioned.) [1] hydrogen formed at cathode (negative electrode); (note: can be awarded from a correct or incorrect equation with H2 as the only substance on the right as long as cathode is mentioned.) [1]

one correct half equation either 2Cl – → Cl2 + 2e or 2H+ + 2e → H2 [1]

solution remaining contains Na+ and OH– / sodium and hydroxide ions / NaOH / sodium hydroxide left behind/remains in solution; [1] note: if a mercury cathode is specified

electrolysis / electrolyte / electrodes / anode / cathode / electricity / cell; [1] chlorine formed at anode (positive electrode); (note: can be awarded from a correct or incorrect equation with Cl2 as the only substance on the right as long as anode is mentioned.) [1] sodium formed at cathode; (note: can be awarded from a correct or incorrect equation with Na as the only substance on the right as long as cathode is mentioned.) [1]

one correct half equation at anode i.e. 2Cl – → Cl2 + 2e or at cathode Na+ + e → Na

(accept: equivalent with NaHg amalgam) [1] NaOH/sodium hydroxide is formed by sodium/sodium mercury amalgam reacting with or when added to water; [1] note: award the fourth and fifth mark if correct equation given for reaction between sodium or sodium mercury amalgam reacting with water i.e.

2Na(Hg) + 2H2O → 2NaOH + H2 + (2Hg)

(ii) H2 / H / hydrogen and making ammonia / making margarine / hardening fats / fuel /

energy source / cryogenics / welding; [1] Cl2 / Cl / chlorine and (making) bleach / water treatment / kill bacteria (in water) / water purification / swimming pools / making solvents / making PVC / making weed killer / making disinfectants / making hydrochloric acid / HCl / making herbicides / pesticides / insecticides; [1]




5 (a) (i) correct -O- linkage; [1] correct unit and continuation -O-�- (minimum); [1]

(ii) any name or correct formula of a (strong) acid / H+; [1] (iii) contain carbon hydrogen and oxygen /C, H and O; [1]

(b) (i) glucose → ethanol + carbon dioxide [1] (ii) yeast is catalyst / provides enzymes / speeds up reaction / too slow without yeast; [1]

yeast cells grow / multiply / reproduce / undergo budding / breed; [1] (iii) heat or high temperature would kill yeast (cells) / heat or high temperature denatures

enzymes; [1] not: enzyme killed / denatures yeast reduces rate of reaction / slows reaction / (yeast or enzyme) no longer catalyses / no catalyst / stops reaction / no more product; [1]

(c) (i) would produce carbon dioxide or carboxylic or organic acids (if oxygen is present) / to

prevent aerobic respiration / so products are not oxidised / anaerobic bacteria can’t live with oxygen; [1]

(ii) fossil fuels have a reduced need / conserved / no need to import / will last longer /

cracking hydrocarbons to make methane no longer required; (methane) is renewable / carbon neutral;

reduce pollution of water or sea / prevents visual pollution / prevents need for waste disposal or accumulation (accept: any methods of waste disposal) / so that waste is recycled; any two [2]

6 (a) (i) A C D B [1] (ii) speed (or rate) increases as concentration increases / time decreases as concentration

increases; [1] rate or speed or time depends on (concentration) of H+ or hydrogen ions; [1] B is slow because propanoic acid is weak or doesn’t dissociate or weakly ionises; or B is slow because HCl and H2SO4 are stronger or ionise or dissociate more than propanoic; [1] D slower than C because C is more concentrated than D / ORA; [1] A is fast because H+ concentration high (note: this would also score second mark if not already awarded) / H2SO4 is diprotic or dibasic or 2H+; [1] time is inversely proportional to rate / owtte / ORA; [1] max [5]




(b) change 1: increase temperature / heat (the mixture); [1]

particles/molecules/ions have more energy or move faster; [1] more (successful) collisions / more particles with Ea; [1] change 2: increase surface area / decrease particle size / use powdered (magnesium) / use smaller pieces / crush the magnesium; [1] more collisions / more particles exposed to reaction; [1]

or catalyst; [1]

more (successful) collisions; [1] lowers Ea; [1] max [5]

7 (a) (i) CH2/H2C [1] (ii) same ratio of C:H (atoms) / all cancel to CH2 / because general formula is CnH2n / same

ratio of atoms or elements (in the compound) / C:H ratio is 1:2; [1] (b) (i) propanoic / propionic (acid); [1]

ethanoic / acetic (acid); [1] (ii) formula of ethene / but-2-ene / any symmetrical alkene; [1] (c) (i) CH3CH(Br)CH2Br [1] (ii) CH3CH(OH)CH3 / CH3CH2CH2OH / C3H7OH [1] (d)

correct unit; [1] accept: more than one repeat unit continuation bonds at both ends; [1]

(e) if C5H10 is given award 3 marks;;; [3]

if C10H20 is given award 2 marks;; if 1:7.5:5 / 2:15:10 is given award 2 marks;; in all other cases a mark can be awarded for moles of O2 (= 2.4/32 =) 0.075 AND moles of CO2 (= 2.2/44 =) 0.05;

2C5H10 + 15O2 → 10CO2 + 10H2O [1] accept: multiples including fractions allow: ecf for correct equation from any incorrect alkene




8 (a) proton donor; [1] (b) equal concentrations of both (solutions); [1]

add Universal indicator / determine pH / pH paper; [1] ethylamine has lower pH / ORA; [1] or equal concentration of both (solutions); [1] measure conductivity of aqueous ethylamine and sodium hydroxide; [1] ethylamine will have lower conductivity / sodium hydroxide will have higher conductivity; [1]

(c) add strong(er) base / NaOH / KOH; [1]

warm / heat; [1] (d) (ethylamine forms) hydroxide ions / OH– (in water); [1]

hydroxide ions / OH– reacts with iron(III) ions / Fe3+; or iron(III) hydroxide / Fe(OH)3 (forms as a brown precipitate); [1]

note: balanced or unbalanced ionic equation i.e. Fe3+ + (3)OH– → Fe(OH)3 scores both marks





0620 CHEMISTRY









1 (a) neon has full outer shell / energy level / valency shell / octet / 8 (electrons) in outer shell / neon does not need to lose or gain electrons; [1] fluorine atoms have 7 electrons / needs 1 to fill / has incomplete shell / forms bonds with other fluorine atoms / fluorine (atoms) form covalent bonds / shares electrons; [1]

(b) atomic number / proton number / number of protons (in one atom); [1] (c) weak intermolecular (or between molecules) forces / Van der Waals forces between

molecules / low amount of energy required to break bonds between molecules; [1] strong bonds don’t break / covalent bonds don’t break / (unnamed) bonds within molecules / between atoms don’t break; [1]

(d) 1 non-bonding pair on each nitrogen atom; [1]

6 electrons between nitrogen atoms; [1] 2 (a) weak forces between layers or between (hexagonal) rings / weak bonds between layers or

between (hexagonal) rings / Van der Waals forces between layers or between (hexagonal) rings; [1] (layers/rings) slip/slide (over each other) / move over each other [1]

(b) strong bonds (between atoms) / covalent bonds (between atoms); [1]

all bonds are covalent/strong / each atom covalently bonded / carbon (atoms) is bonded to four others / bonds are directional / (atoms are arranged) tetrahedrally; [1]

accept: carbon has four bonds (c) graphite has delocalised / mobile / free electrons; [1]

diamond (outer shell) electrons used / fixed / localised in bonding / no delocalised electrons / no mobile electrons / no free electrons; [1]

3 (a) flexible / easily form different shapes / easily moulded / bends (without cracking); [1]

non-biodegradable / unreactive / don’t corrode / prevent corrosion / prevent oxidation (of the conducting metal) / water resistant / waterproof; [1]

(b) improve appearance / decorative / makes appearance shiny; [1]

prevent corrosion / rusting / protect steel / chromium will not corrode / chromium is not oxidised / chromium protected by an oxide layer; [1]

(c) low density / light / protected by oxide layer / no need to paint / resists corrosion / (high)

strength / strong;; any two [2] note: high strength to weight ratio = 2

(d) high mpt / withstands high temperature / good conductor (of heat) / heats up quickly /

malleable / ductile / resists corrosion / good appearance / unreactive (or example of lack of reactivity e.g. does not react with food or water or acid or air);; any two [1]




(e) (lattice) positive ions / cations / metal ions and sea of electrons / delocalised or free or mobile or moving electrons; [1] attraction between positive ions and electrons; [1]

4 (a) (i) oxygen; [1]

carbon dioxide / fluorine / carbon monoxide; [1] (ii) decrease mpt (of alumina/Al2O3) / lower (operating) temperature (from 1900/2100 (°C) to

800/1000 (°C) / reduce energy (accept heat or electrical) requirement; [1] improve conductivity / dissolves the Al2O3 / acts as solvent; (allow: makes aluminium oxide conduct / to conduct electricity / making ions free to move) [1]

(iii) Al2O3 (accept alumina) reacts / dissolves / forms a salt and water / is neutralised; [1]

(Fe2O3 removed by) filtration / centrifugation / decantation; [1] (b) (i) electrolysis / electrolyte / electrodes / anode / cathode / electricity / cell; [1]

chlorine formed at anode (positive electrode); (note: can be awarded from a correct or incorrect equation with Cl2 as the only substance on the right as long as anode is mentioned.) [1] hydrogen formed at cathode (negative electrode); (note: can be awarded from a correct or incorrect equation with H2 as the only substance on the right as long as cathode is mentioned.) [1]

one correct half equation either 2Cl – → Cl2 + 2e or 2H+ + 2e → H2 [1]

solution remaining contains Na+ and OH– / sodium and hydroxide ions / NaOH / sodium hydroxide left behind/remains in solution; [1] note: if a mercury cathode is specified

electrolysis / electrolyte / electrodes / anode / cathode / electricity / cell; [1] chlorine formed at anode (positive electrode); (note: can be awarded from a correct or incorrect equation with Cl2 as the only substance on the right as long as anode is mentioned.) [1] sodium formed at cathode; (note: can be awarded from a correct or incorrect equation with Na as the only substance on the right as long as cathode is mentioned.) [1]

one correct half equation at anode i.e. 2Cl – → Cl2 + 2e or at cathode Na+ + e → Na

(accept: equivalent with NaHg amalgam) [1] NaOH/sodium hydroxide is formed by sodium/sodium mercury amalgam reacting with or when added to water; [1] note: award the fourth and fifth mark if correct equation given for reaction between sodium or sodium mercury amalgam reacting with water i.e.

2Na(Hg) + 2H2O → 2NaOH + H2 + (2Hg)

(ii) H2 / H / hydrogen and making ammonia / making margarine / hardening fats / fuel /

energy source / cryogenics / welding; [1] Cl2 / Cl / chlorine and (making) bleach / water treatment / kill bacteria (in water) / water purification / swimming pools / making solvents / making PVC / making weed killer / making disinfectants / making hydrochloric acid / HCl / making herbicides / pesticides / insecticides; [1]




5 (a) (i) correct -O- linkage; [1] correct unit and continuation -O-�- (minimum); [1]

(ii) any name or correct formula of a (strong) acid / H+; [1] (iii) contain carbon hydrogen and oxygen /C, H and O; [1]

(b) (i) glucose → ethanol + carbon dioxide [1] (ii) yeast is catalyst / provides enzymes / speeds up reaction / too slow without yeast; [1]

yeast cells grow / multiply / reproduce / undergo budding / breed; [1] (iii) heat or high temperature would kill yeast (cells) / heat or high temperature denatures

enzymes; [1] not: enzyme killed / denatures yeast reduces rate of reaction / slows reaction / (yeast or enzyme) no longer catalyses / no catalyst / stops reaction / no more product; [1]

(c) (i) would produce carbon dioxide or carboxylic or organic acids (if oxygen is present) / to

prevent aerobic respiration / so products are not oxidised / anaerobic bacteria can’t live with oxygen; [1]

(ii) fossil fuels have a reduced need / conserved / no need to import / will last longer /

cracking hydrocarbons to make methane no longer required; (methane) is renewable / carbon neutral;

reduce pollution of water or sea / prevents visual pollution / prevents need for waste disposal or accumulation (accept: any methods of waste disposal) / so that waste is recycled; any two [2]

6 (a) (i) A C D B [1] (ii) speed (or rate) increases as concentration increases / time decreases as concentration

increases; [1] rate or speed or time depends on (concentration) of H+ or hydrogen ions; [1] B is slow because propanoic acid is weak or doesn’t dissociate or weakly ionises; or B is slow because HCl and H2SO4 are stronger or ionise or dissociate more than propanoic; [1] D slower than C because C is more concentrated than D / ORA; [1] A is fast because H+ concentration high (note: this would also score second mark if not already awarded) / H2SO4 is diprotic or dibasic or 2H+; [1] time is inversely proportional to rate / owtte / ORA; [1] max [5]




(b) change 1: increase temperature / heat (the mixture); [1]

particles/molecules/ions have more energy or move faster; [1] more (successful) collisions / more particles with Ea; [1] change 2: increase surface area / decrease particle size / use powdered (magnesium) / use smaller pieces / crush the magnesium; [1] more collisions / more particles exposed to reaction; [1]

or catalyst; [1]

more (successful) collisions; [1] lowers Ea; [1] max [5]

7 (a) (i) CH2/H2C [1] (ii) same ratio of C:H (atoms) / all cancel to CH2 / because general formula is CnH2n / same

ratio of atoms or elements (in the compound) / C:H ratio is 1:2; [1] (b) (i) propanoic / propionic (acid); [1]

ethanoic / acetic (acid); [1] (ii) formula of ethene / but-2-ene / any symmetrical alkene; [1] (c) (i) CH3CH(Br)CH2Br [1] (ii) CH3CH(OH)CH3 / CH3CH2CH2OH / C3H7OH [1] (d)

correct unit; [1] accept: more than one repeat unit continuation bonds at both ends; [1]

(e) if C5H10 is given award 3 marks;;; [3]

if C10H20 is given award 2 marks;; if 1:7.5:5 / 2:15:10 is given award 2 marks;; in all other cases a mark can be awarded for moles of O2 (= 2.4/32 =) 0.075 AND moles of CO2 (= 2.2/44 =) 0.05;

2C5H10 + 15O2 → 10CO2 + 10H2O [1] accept: multiples including fractions allow: ecf for correct equation from any incorrect alkene




8 (a) proton donor; [1] (b) equal concentrations of both (solutions); [1]

add Universal indicator / determine pH / pH paper; [1] ethylamine has lower pH / ORA; [1] or equal concentration of both (solutions); [1] measure conductivity of aqueous ethylamine and sodium hydroxide; [1] ethylamine will have lower conductivity / sodium hydroxide will have higher conductivity; [1]

(c) add strong(er) base / NaOH / KOH; [1]

warm / heat; [1] (d) (ethylamine forms) hydroxide ions / OH– (in water); [1]

hydroxide ions / OH– reacts with iron(III) ions / Fe3+; or iron(III) hydroxide / Fe(OH)3 (forms as a brown precipitate); [1]

note: balanced or unbalanced ionic equation i.e. Fe3+ + (3)OH– → Fe(OH)3 scores both marks



MARK SCHEME for the May / June 2012 question paper


0620 CHEMISTRY

0620 / 51 Paper 5 (Practical), maximum raw mark 40



• Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May / June 2012 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.





1 (a) Table of results volume of aqueous potassium chloride boxes completed correctly (1) 1,2,4,5, 6 and 7 heights of solid boxes completed (1) in mm (1) ascending order / last 2 level out (1) [4]

(b) all points correctly plotted including origin (2), –1 for any incorrect

appropriate scale for y axis(at least half of grid) (1) best fit straight line graph drawn with a ruler(1) [4] (c) value from graph (1) unit (1) shown clearly (1) [3] (d) precipitation / double decomposition (1) [1] (e) height increases(1) levels off (1) [2] (f) same heights owtte (1) ` all lead nitrate reacted / / reaction finished / excess potassium chloride (1) [2] (g) yellow precipitate / solid (1) [1] (h) improvement (1) e.g. use burette or pipette / leave solid to settle longer / repeat / wider range of volumes for KCl explanation (1) e.g. instead of a measuring cylinder / heights more accurate / take average / more reliable / accurate [2] 2 (a) white (1) [1] (b) (i) condensation / drops of liquid / water / steam (1) solid is still white no (colour) change (1) [2] fizzes / effervescence (1) lighted splint extinguished / owtte (1) [2] (ii) fizz / bubbles / effervescence (1) limewater(1) milky / cloudy / white precipitate (1) [3] (iii) effervescence / fizz / bubbles (1) darkens / turns black / green (1) ignore: blue [2] (iv) description of smell of ammonia / sublimate (1) pH paper turns blue / green or pH > 7 (1) allow: litmus goes blue [2]




(c) initial temperature recorded (1) oC (1) final temperature recorded and lower (1) [3] pH > 7 (1) [1] (d) carbon dioxide (1) [1] (e) ammonia (1) not: ammonium [1] (f) endothermic (1) [1] (g) hydrogencarbonate / carbonate (1) alkaline (1) not: sodium hydroxide non transition metal (1) max 2 [2]





0620 CHEMISTRY









1 (a) experiment 1 all boxes completed (1) results show a regular pattern (1) [2]

(b) experiment 2 all boxes completed (1)

results show a regular pattern (1) [2] (c) all points correctly plotted (+/– ½ small square) (2), –1 for any incorrect

Should have a y axis: linear scale and points extend over at least 4 big squares (8 cm) (1) two × smooth lines (curved or straight) (2) both lines labelled (1) [6]

(d) (i) value from graph (+/– ½ small square) (1) shown clearly (1) [2] (ii) value from graph (+/– ½ small square) (1) shown clearly (1) [2] (e) endothermic (1) [1] (f) lower temperature (changes) (1)

greater volume/more water (1) [2] (g) room temperature or initial temperature from table (1)

reaction finished/all dissolved/warms up (1) [2] (h) more readings/points (1)

better graph/more reliable/more accurate/owtte (1) [2] [Total: 21]




2 (a) green (1) reject: any other colours, ignore: dark/light [1] (b) (turns) black (1) condensation/drops at top of tube/steam/water (1)

limewater (1) milky/cloudy/white ppt (1) max 3 [3] (c) (i) fizz/bubbles etc. (1)

blue solution/liquid (1) [2] (ii) blue (1) ignore: qualifiers such as dark/light precipitate (1) [2]

blue precipitate (1) (ignore qualifiers such as dark/light) dark/royal/deep blue (1) must be some indication it is darker than the ppt solution/soluble/dissolves (1) [3]

(d) appearance: colourless (1)

smell: vinegar/pungent/sharp/sour/strong (1) [2] (e) pH2–6 (1) [1] (f) green or blue-green solution/liquid (1)

fizz/bubbles (1) [2] (g) copper (1) carbonate (1) [2] (h) acid/organic/ethanoic/acetic/vinegar [1] [Total: 19]





0620 CHEMISTRY









1 (a) experiment 1 all boxes completed (1) results show a regular pattern (1) [2]

(b) experiment 2 all boxes completed (1)

results show a regular pattern (1) [2] (c) all points correctly plotted (+/– ½ small square) (2), –1 for any incorrect

Should have a y axis: linear scale and points extend over at least 4 big squares (8 cm) (1) two × smooth lines (curved or straight) (2) both lines labelled (1) [6]

(d) (i) value from graph (+/– ½ small square) (1) shown clearly (1) [2] (ii) value from graph (+/– ½ small square) (1) shown clearly (1) [2] (e) endothermic (1) [1] (f) lower temperature (changes) (1)

greater volume/more water (1) [2] (g) room temperature or initial temperature from table (1)

reaction finished/all dissolved/warms up (1) [2] (h) more readings/points (1)

better graph/more reliable/more accurate/owtte (1) [2] [Total: 21]




2 (a) green (1) reject: any other colours, ignore: dark/light [1] (b) (turns) black (1) condensation/drops at top of tube/steam/water (1)

limewater (1) milky/cloudy/white ppt (1) max 3 [3] (c) (i) fizz/bubbles etc. (1)

blue solution/liquid (1) [2] (ii) blue (1) ignore: qualifiers such as dark/light precipitate (1) [2]

blue precipitate (1) (ignore qualifiers such as dark/light) dark/royal/deep blue (1) must be some indication it is darker than the ppt solution/soluble/dissolves (1) [3]

(d) appearance: colourless (1)

smell: vinegar/pungent/sharp/sour/strong (1) [2] (e) pH2–6 (1) [1] (f) green or blue-green solution/liquid (1)

fizz/bubbles (1) [2] (g) copper (1) carbonate (1) [2] (h) acid/organic/ethanoic/acetic/vinegar [1] [Total: 19]





0620 CHEMISTRY









1 (a) tripod (1) accept: stand spatula (1) not: spoon [2] (b) fizz/bubbles/effervescence stops (1) solid/iron/powder visible / no more iron dissolves/reacts (1) [2] (c) evaporation of water/steam (1) solid/residue/crystals formed (1) colour change turns brown/darker green (1) effect of heat on solid solid breaks down (1) max 3 [3] [Total: 7] 2 (a) thermometer readings correct (3), –1 for any incorrect methanol 25 28 3 ethanol 26 39 13 propanol 23 46 23 butanol 24 58 34 temperature rises correct (1) [4] (b) points plotted correctly ±1/2 small square (3) straight line drawn with a ruler (1) [4] (c) value from graph (1) unit (1) 44°C extrapolation shown on grid (1) [3] (d) temperature rises would be greater/faster/quicker (1) copper is a good conductor (1) [2] [Total: 13] 3 (a) pestle (1) mortar (1) [2] (b) stir/mix/shake (1) allow: heat/boil [1] (c) diagram showing funnel (1) indication of filter paper (1) note: labels not necessary [2] (d) heat/evaporation (1) to crystallising point or description (1) in fume cupboard (1) max 2 [2] (e) melting point/description of (1) allow: chromatography ignore: bp [1] [Total: 8]




4 (a) Table of results ignore: units in table volume of aqueous potassium chloride boxes completed correctly (1) 1, 2, 4. 5, 6, 7 heights of solid boxes completed ±1mm (2) 4, 8, 16, 20, 24, 24 in mm (1) [4] (b) all points correctly plotted (2), –1 for any incorrect straight line graphs (2) note: one for each line, doesn’t have to go through origin [4] (c) value from graph 14 (1) unit (1) shown clearly (1) [3]

(d) precipitation (1) allow: double decomposition ignore: exo/endothermic [1] (e) (i) same (1) no ecf not: almost the same all lead nitrate reacted/reaction finished/lead nitrate is limiting factor (1) [2] (ii) same heights/owtte (1) lead nitrate is limiting factor/same amount of lead nitrate/excess potassium chloride (1)

[2] (g) yellow (precipitate) (1) [1] (h) improvement (1) e.g. use burette/pipette/leave solid to settle longer/repeat explanation (1) e.g. instead of a measuring cylinder/heights more accurate/take average [2] [Total: 19] 5 (c) fizz/bubbles/effervescence (1) limewater (1) milky/cloudy/white ppt (1) cond: on limewater [3] (e) ammonia (1) [1] (f) non-transition metal (1) ammonium (salt or carbonate) (2) not: ammonia max [2] [Total: 6] 6 steel nail(s) in test-tube/suitable glass container (1) x

cm3 (1) water (1) no water = max 3 known volume of inhibitor added (1) observe effect after suitable time (1) note: minimum time = 1 day repeat using other inhibitors (1) observe/comparison of results (1) [7] [Total: 7]





0620 CHEMISTRY









1 (a) beaker (1) [1] (b) any through tube with (only) two open ends (1) outer tube with ‘water’ labelled and a way in and out (1) [2] (c) turns red/pink (1) reversible/rehydration/owtte/CoCl2 going pink is the test for water (1) [2] (d) water condensed at top of tube (1) runs back onto hot tube/water onto CoCl2 generates heat/owtte (1) not: suck back [2] [Total: 7] 2 (a) smooth curve starting at origin and missing anomalous point (1) [1] (b) point at 1.5 min/4th point/0.32 g (1) ignore: 3rd point [1] (c) reaction finished/no more gas (1) magnesium carbonate used up (1) [2] (d) rising part of sketch curve below the original/less steep (1) to half final level/0.25 g (1) [2] [Total: 6] 3 (a) bulb/lamp lights/water level falls/green-yellow gas (1) [1] (b) arrows labelling electrodes as anode/cathode or + – or the electrodes or Pt (1) allow: labels either way round not: the wires labelled [1] (c) (i) hydrogen (1) [1] (ii) lighted splint (1) if Cl2 in (c)(i) allow ecf for damp litmus/indicator paper

no ecf for anything other than Cl2 pops (1) if Cl2 in (c)(i) allow ecf for bleached/white/decolourised [2] note: These are conditional marks so the result is conditional on the test, i.e. glowing

splint pops = 0/2 (d) chlorine (1) soluble/dissolves/reacts (1) [2] [Total: 7]




4 (a) fizzing/bubbles stopped/no more gas produced (1) [1] (b) (i) W little/no effect/slight increase (1) X no effect/(slight) decrease (1) Y speeds up reaction (1) [3] note: The question is about rate, if candidates quote three different time differences,

penalise first then allow the ‘correct’ answers (–11 s, +2 s, –199 s). It must be clear that the increase in rate is less for W than Y for these 2 marks. (ii) Y (1) [1] (c) repeat experiments (1) take average/compare results/see if there is a difference (1) [2] [Total: 7] 5 (a) temperature boxes correctly completed (2) 21, 25, 26, 27, 27, 26, 25 [2] (b) temperature boxes completed correctly (2) 20, 19, 18, 17, 17, 18, 19 [2] (c) all points correctly plotted (3), –1 for any incorrect smooth line graphs (2) labels (1) [6] (d) (i) value from graph (1) allow: ±1/2 small square shown clearly (1) [2] (ii) value from graph (1) allow: ±1/2 small square shown clearly (1) [2] (e) endothermic (1) ignore: temperature decreases [1] (f) lower temperature (change)/halved (1) ignore: reference to rate/time [1] (g) room temperature/initial temperature from table/20°C/21°C (1) ignore: 25°C reaction finished/owtte (1) [2] (h) more readings/more points (1) more reliable/more accurate (1) ignore: precise can spot anomalous points or errors (1) smoother graph/owtte (1) any [2] [Total: 20]




6 (d) appearance colourless (1) ignore: clear smell vinegar/pungent/sour/sharp (1) ignore: sweet/strong [2] (e) pH 2–6 (1) [1] (f) carbon dioxide (1) [1] (g) copper/Cu2+ (1) carbonate/CO3

2– (1) [2] [Total: 6] 7 (a) use Universal/pH indicator/pH meter (1) ignore: litmus/indicator [1] (b) note: This can be marked via three routes.

If they use a full bottle: use full bottle (1) (air-tight) connections (1) syringe/inverted measuring cylinder/graduated tube to collect gas (1) heat/shake (1) until no more gas given off (1) measure volume of gas (1) any 6 If they use a sample: use measured volume (1) (air-tight) connections (1) syringe/inverted measuring cylinder/graduated tube to collect gas (1) heat/shake (1) until no more gas given off (1) measure volume of gas (1) multiply to get full bottle value (1) max 6 If they do it by loss in mass: weigh the bottle/sample (1) heat/shake (1) until no more gas given off (1) reweigh bottle (1) use density to calculate volume (1) max 5 [6]

[Total: 7]





0620 CHEMISTRY









1 (a) teat/dropping pipette/dropper (1) allow: pipette [1] (b) crushed ore would have larger surface area (1) more zinc oxide would have formed/faster decomposition (1) [2] (c) sulfuric (1) [1] (d) filtration (1) [1] (e) add magnesium (1) allow: electrolysis [1] [Total: 6] 2 bromine (water) (1) not: bromide colourless (1) aqueous silver nitrate (1) yellow precipitate (1) named indicator/solution of copper salt (1) correct colour change/pH/blue precipitate (1) [6] [Total: 6] 3 (a) volumes completed correctly 0, 30, 45, 52, 56, 54, 60, 60 –1 for each incorrect [3] (b) points plotted correctly (3) –1 for each incorrect smooth curve (1) [4] (c) point at 100 seconds/54 cm3/point 6 (1) off curve/owtte (1) [2] (d) 20 cm3 ±½ small square (1) indication on graph (1) [2] (e) reaction finished/all peroxide decomposed owtte (1) [1] (f) (i) in an ice bath (1) allow: in a refrigerator [1] (ii) curve less steep (1) to same level (1) [2] [Total: 15]




4 (a) pipette/burette (1) [1]

(b) (i) methyl orange/phenolphthalein/litmus (1) not: Universal Indicator (ii) yellow/pink to orange or pink/colourless (1) [2]

(c) nitric acid (1) more volume added than sodium hydroxide (1) [2]

(d) repeat experiment (1) without indicator (1) evaporate solution (1) [3]

[Total: 8]

5 (c) bubbles/fizz/effervescence (1) [1] limewater (1) milky (1) [2]

(d) (i) blue (1) precipitate (1) [2] (ii) blue precipitate (1) [1] dark/deep blue (1) solution/dissolves (1) [2]

(e) barium/calcium (1) chloride (1) not: chlorine ions [2]

[Total: 10]

6 (a) Bunsen burner (1) ignore: switch [1]

(b) labels on correct positions (1) [1]

(c) (i) bulb lights/idea of molten lead (1) (ii) bulb goes out/no fizz (1) [2]

(d) pressure of gas build up/explode owtte (1) [1]

(e) iodine formed (1) not: iodide from iodide ions (1) [2]

(f) fume cupboard/well ventilated area (1) allow gloves if reason specified ignore: goggles [1]

[Total: 8]




7 known mass/weight (1) of each fertiliser (1) add to same amount of soil (1) + bean (1) water (1) leave for specified time (1) observe plant growth/effect (1) comparison/conclusion (1) max 7 [7] [Total: 7]



MARK SCHEME for the November 2004 question paper

0620 CHEMISTRY 0620/01 Paper 1 (Multiple Choice), maximum mark 40

Mark schemes must be read in conjunction with the question papers and the Report on the

Examination.

• CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the November 2004 question papers for most IGCSE and GCE Advanced Level syllabuses.


Grade thresholds taken for Syllabus 0620 (Chemistry) in the November 2004 examination.


available A C E F

Component 1 40 35 28 23 19


November 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 40


Chemistry Paper 1 (Multiple Choice)


IGCSE – November 2004 0620 1


Question Number

Key Question Number

Key

1 C 21 C

2 C 22 D

3 B 23 A

4 B 24 B

5 B 25 D

6 D 26 A

7 C 27 C

8 A 28 B

9 C 29 A

10 B 30 C

11 A 31 D

12 C 32 D

13 D 33 A

14 A 34 B

15 B 35 C

16 B 36 B

17 A 37 D

18 A 38 C

19 D 39 C

20 A 40 D




0620 CHEMISTRY 0620/02 Paper 2 (Core Theory), maximum mark 80



Examination.


CIE is publishing the mark schemes for the November 2004 question papers for most IGCSE and GCE Advanced Level syllabuses.




available A C E F

Component 2 80 N/A 52 40 33


November 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 80


CHEMISTRY (Core Theory)




1 (a) increases; some comment that the trend is irregular/only approximate e.g. potassium (or sodium) do not follow the trend/boiling point of sodium high/boiling point of potassium too low [2] (b) allow 670-714oC (actual = 686oC) [1] (c) allow 0.260-0.300 (nm) (actual = 0.272 nm) [1] (d) slower (than sodium)/less rapid/gently etc. ALLOW: slow [1] (e) any three properties from: conduct (heat/electricity); malleable; ductile; shiny; sonorous ALLOW: solid at room temperature NOT: strong; high melting/boiling points; high density [3] (f) (i) sodium hydroxide [1] (ii) lighted splint: pops/explodes/squeaky sound [2] (2nd mark CONDITIONAL on 1st) (g) (i) proton(s) [1] (ii) isotope(s) [1] (iii) 3 [1] (iv) any suitable use e.g. radioactive tracer/cancer therapy/sterilising medical equipment [1] ALLOW: kills bacteria NOT: X-rays 2 (a) A + D [1] (b) C + E [1] (c) C5H10 [1] (d) correct formula for 1,2 – dibromoethane showing all atoms and bonds [1] ALLOW: correct dot and cross diagram




(e) (i) 5 and 6 [1] (ii) respiration [1] (iii) decreases it/slows it ALLOW: ethane breaks down [1] NOT: stops it (iv) diffusion [1] (v) removes the ethene/blows the ethene away/reduces the amount of ethene OWTTE [1] ALLOW: dilutes ethene (vi) biological/protein/description of protein; NOT: an organism/a bacterium/natural catalyst catalyst/description of catalyst [2] (f) (i) chromatography [1] (ii) S [1] (iii) R + T [1] 3 (a) measuring cylinder ALLOW: burette/volumetric pipette [1] NOT: pipette; cylinder (b) so that all the (sulphuric) acid reacted/used up [1] NOT: ensure that reaction is complete (c) carbon dioxide/gas given off [1] NOT: there is a reaction (d) filter funnel; filter paper; beaker underneath [3] -1 mark if at least two parts not correctly labelled If no filter paper = 0 If filter paper shown flat at top of funnel, max =1 (if at least two labels are correct) (e) filtrate [1] (f) evaporate/boil off (some off) the water/allow to crystallise in a warm place/leave in a warm place; NOT: evaporate solution/evaporate nickel sulphate NOT: heat (alone) unless qualified dry with filter paper/pick out crystals and dry; [2] NOT: heat/warm to dry




(g) (i) 7H2O [1] (ii) equilibrium/reversible reaction [1] NOT: goes back to original form/state NOT: goes two ways (iii) add (a little) water [1] 4 (a) nitrogen [1] (b) (i) oxygen; water. [2] NOT: symbols (ii) carbon and hydrogen ALLOW: symbols [1] (iii) alkanes [1] (c) incomplete combustion (of hydrocarbons/fuels)/insufficient oxygen for combustion [1] NOT: lack of oxygen (d) (i) 2 + 2 [1] (ii) any suitable e.g. breathing difficulties/irritation of throat/irritation of lungs/damage to lungs/watering eyes etc [1] NOT: causes lung diseases ALLOW: suitable affects of acid rain if clearly stated that NO2 dissolves in

water first NOT: kills organisms/animals NOT: affects lungs/eyes etc. (e) (i) burning coal ALLOW: burning fossil fuels [1] (ii) addition of oxygen [1] ALLOW: removal/loss of electrons (iii) 98 [1] (iv) iron sulphate/iron(II) sulphate; NOT: iron(III) sulphate hydrogen [2] (v) erodes them/wears them away [1] ALLOW: answers involving relevant chemical reactions (e.g. calcium carbonate + acid) in context NOT: corrodes NOT: deteriorates NOT: cracks them/destroys them




5 (a) (i) increases growth/increases crop yield [1] NOT: for plant growth/helps growth/provides nutrients for growth/ makes them grow faster/better (ii) potassium/K/K+ [1] (iii) phosphate [1] (b) add (aqueous) sodium hydroxide; and aluminium foil/Devarda’s alloy; warm/test with red litmus/smell gas; ammonia produced/pungent smell/litmus turns blue [4] (4th mark only allowed if reagents correct) (warm gains no credit unless reagents correct) OR add iron(II) sulphate; and concentrated: sulphuric acid; brown ring (where the two layers meet) (c) (i) neutralisation/acid-base ALLOW: exothermic [1] (ii) NH3 [1] (d) 2nd and 4th boxes ticked (1 each) [2] 6 (a) 3rd box down ticked [1] (b) (i) breaking down/decomposition of a substance/compound using electricity [1] NOT: separation of ions using electricity (ii) negative/cathode [1] (iii) graphite ALLOW: carbon/platinum [1] NOT: copper (c) (i) electron [1] (ii) (acidify with nitric acid) add silver nitrate solution; white precipitate [2] (d) 2 [1] (e) (i) 2550 [1] (ii) 3.6% [1]




(f) (i) unsaturated; catalyst; saturated [3] (ii) any suitable use e.g. fuel/specific reductions (e.g. alkenes (to alkanes)/Haber process) [1] ALLOW: in balloons/airships/rockets ALLOW: in making hydrochloric acid ALLOW: in oxy-hydrogen blowpipe NOT: making water/making margarine






Examination.





available A C E F

Component 3 150 52 34 25 19


November 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 150


CHEMISTRY Extended Theory




1 (a) carbon dioxide, water vapour, noble gases or a named noble gas Any TWO [2] (b) burning fossil fuels [1] COND that contain sulphur [1] acid rain or any effect of acid rain - deforestation, effect on stone work, corrosion of metals, acidity in lakes, health etc [1] motor vehicles or petrol or car exhausts [1] health, if specified then brain, nervous system, development of children etc [1] do not select from list illnesses OR lead in old paint [1] harmful effect as above [1] (c) (i) combustion or burning NOT dissolving in the ocean [1] (ii) 6CO2 + 6H2O [1] exothermic [1]

(d) (i) glowing splint burst into flame or rekindled [1] Must have glowing or equivalent idea OR any similar description that includes the two points glowing and relights.

(ii) measure volume or count bubbles [1] time [1] NOT units (iii) rate slows down [1]

Because the reaction is photochemical or rate depends on intensity of light or light less bright or less light falling on plant or light provides energy for photosynthesis etc. [1]

TOTAL = 15 2 dilute

filter saturated cool blue sulphate [6] TOTAL = 6

3 (a) (i) no change in concentration of reagents or rates equal [1]

Accept no change in amounts or it is as if the reaction has Stopped

(ii) back reaction is endothermic or the forward reaction is exothermic [1] Increase in temperature favours the endothermic reaction which is the back reaction or vice versa. [1] NB look for correct conclusion re thermicity and comment re position of

equilibrium.




(iii) increased rate [1] because molecules collide more frequently or concentration of molecules is increased or molecules are closer [1] NOT they have more KE increased yield [1] high pressure favours side with few molecules or smaller volume or moves to reduce the pressure [1] this is product side this can be implied [1]

(b) (i) CO2 and H2O [1]

balanced [1] 2CH3OH + 3O2 = 2CO2 + 4H2O

(ii) methyl ethanoate [1] water [1] (iii) Methanoic (acid) accept formic acid [1] TOTAL = 13

4 (a) (i) Correct equation with a more reactive metal [1]

(ii) Electron loss [1]

(iii) Because they can accept electrons or take electrons away from……. [1]

(iv) Silver or silver(I) [1] (b) (i) increase [1]

(ii) zinc COND and a correct reason - such as it loses electrons more easily or it is more reactive [1] Need both zinc and reason for the mark. (iii)from the more reactive to the less reactive NOT just from zinc to lead [1]

TOTAL = 7 5 (a) Group II metals will lose 2e [1] Group VI elements will gain 2e [1] (b) SCl2 [1] COND 8e around both chlorine atoms [1]

8e around sulphur with 2nbp and 2bp [1]

If x and o reversed ignore if this is the only error

(c) (i) Ions cannot move in solid or can move in liquid [1] (ii) No ions in sulphur chloride or it is covalent or only molecules or only strontium chloride has ions [1] TOTAL = 7




6 (a) (i) correct structure [1] CH2=CCl2

(ii) because it has a lower Mr or density or its molecules move faster [2] it is lighter ONLY [1] only comment - smaller molecules [0] answer implies or states sieve idea then [0] (b) (i) ester linkage [1] COND polymer chain showing different monomers and

continuation [1] -OOC-C6H4-COOCH2CH2O-

(ii) fats or lipids [1] (iii) does not decompose easily when heated [1] accept similar statements

(c) (i) does not decompose or non-biodegradable shortage of landfill sites or of space visual pollution poisonous/toxic/harmful gases when burnt NOT carbon monoxide, sulphur dioxide. If gas named has to be a correct one eg HCl, HCN dangerous to animals Any TWO [2]

(ii) conserve petroleum or save energy [1] NOT cheaper TOTAL = 10

7 (a) (i) Zn(OH)2 = ZnO + H2O [2] reactant [1] products [1]

(ii) it would melt or it does not decompose or it does not react [1] NOT no change (iii) blue (solid) [1]

to black (solid) [1] brown gas [1]

Mark consequentially to any error but not involving simple integers There has to be some evidence that the candidate has attempted to work through the calculation and not merely inserted whole numbers. For example 2, 1, 160 or 1, 0.5, 80 number of moles of Fe2(SO4)3 = 1/40 or 0.025 number of moles of Fe2 O3 formed = 1/40 or 0.025 mass of iron(III) oxide formed = 0.025 x 160 = 4g number of moles of SO3 produced = 3/40 or 0.075 volume of sulphur trioxide at r.t.p. = 0.075 x 25

= 1.8dm3 [5] TOTAL = 11




8 (a) (i) C6H12 [1] between 60 to 65°C [1] (ii) C12H24 [1] COND giving some indication of the method [1] (b) add bromine water or potassium manganate(VII) [1]

butene it goes from brown/orange/yellow to colourless or manganate (VII) from pink to colourless [1] NOT clear Cyclobutane it remains brown/orange/yellow or manganate (VII) stays pink or no colour change [1] Accept does not react Provided colour of reagent somewhere in the answer [3] is possible

(c) (i) alcohol [1] (ii) CH3-CH2-CHCl-CH3 [1]

(iii) -CH(CH3)-CH(CH3)- [2] or any equivalent diagram [1] for repeat unit and [1] for continuation TOTAL = 11




0620 CHEMISTRY 0620/05 Paper 5 (Practical Test), maximum mark 40


Examination.





available A C E F

Component 5 40 32 27 23 20


November 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 40


CHEMISTRY

Practical Test




1 Table of results initial temperatures completed (1) final temperatures completed (1) decreasing (1) comparable to supervisors (2) (5) (a) Graph. Points correctly plotted (3), -1 for each incorrect straight line (1) (4)

(b) (i) temperature for 3.5 g from graph (1) indication (1) (2)

oC (1) (1)

(ii) temperature for 6 g from graph (1) extrapolation (1) (2)

(c) endothermic (1) (1) (d) lower temperature changes (1) more dilute/water to heat up (1) (2) (e) larger surface area (1) dissolves faster/easier (1) (2) (f) initial temperature from table ± 2 oC (1) room temperature/reaction finished (1)(2) (g) change to apparatus e.g. insulation/burette/pipette etc. (1) (1) sub total 22

2 (a) white (1) powder/crystals (1) not precipitate (2) (b) indicator paper goes blue (1) red (1) smell/solid is smaller (1) max 2 (2) white deposit (1) on tube e.g. top/side (1) ( (c) pH 4-6 (1) (1) (d) (i) white (1) precipitate (1) (2) (ii) white (1) precipitate (1) (2) (iii) pH greater than 7 (1) reference to smell/colour of indicator paper (1) (2) (e) ammonia (1) (1) (f) alkaline gas (1) ammonia named (2) sublimation (1) max 2 (2) (g) ammonium (1) chloride (1) (2) sub total 18 Total 40






Examination.





available A C E F

Component 6 60 46 37 29 23


November 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 60


CHEMISTRY





1 (a) A measuring cylinder (1) B flask (1) (2) (b) boxes completed correctly, zinc and hydrochloric acid (1) (1) (c) lighted splint (1) pops (1) second mark consequential i.e. glowing splint = 0 (2) 2 (a) smooth line/curve (1) (1) (b) result at 60s (1) not on curve or similar (1) (2) (c) calcium carbonate is being used up/acid gets more dilute (1) (1) 3 (a) to absorb/hold/contain the liquid (1) (1) (b) cracking (1) (1) (c) bromine (water) (1) colourless (1) (2)

(d) remove the delivery tube from the water (1)

to prevent suck-back or similar effect (1) (2)

4 Table of results

initial temp. 24 23.5 24.5 23 22.5 23

final temp. − 20.5 17.5 14 11 7.5

All 11 temperatures recorded correctly (5), -1 for each incorrect (5) (a) Graph points plotted correctly (3), -1 for each incorrect straight line (1) (4)

(b) (i) temperature from graph (1) e.g. 12.5oC ± 0.5 (1)

indication (1) oC (1) (2) (ii) temperature from graph (1) e.g. 4oC ± 0.5

extrapolation shown (1) (2)

(c) endothermic (1) (1) (d) temperature changes would be smaller (1) more water (1) (2) (e) larger surface area (1) reacts/dissolves faster/easier (1) (2)




(f) 22 - 24oC/room temperature (1) reaction finished (1) (2) (g) use a burette/pipette instead of measuring cylinder/insulation/lids/lags (1) (1)

5 (a) white (1) crystals/solid (1) (2) (c) (i) white (1) precipitate (1) (2) (ii) white (1) precipitate (1) (2) (iii) reference to smell (1) alkaline/blue (1) pH 9 → 12 (1) 2 max (2) (d) ammonia (1) (1) (e) alkaline gas/ammonia given off (1) acid gas/hydrogen chloride given off (1) (2)

6 (a) litmus/indicator (1) bleached in chlorine, no effect with sodium chloride (1) (2)

(b) sodium hydroxide (1) green (precipitate) with iron(II), brown (precipitate) with iron(III) (1) (2)

(c) add hydrochloric acid (1) fizz/bubbles with carbonate, no reaction with sulphate (1) (2)

alternative with HCl and barium chloride (1)

white precipitate with sulphate, not carbonate (1)

7 chromatography (1) apply inks/spots to paper (1) organic solvent/water (1) rises up paper (1) check heights/positions of spots (1) compare to find ink from banknote (1) (6) N.B. all marks can be obtained from a diagram Total marks for paper 60




0620 CHEMISTRY

0620/01 Paper 1 (Multiple Choice),

maximum raw mark 40

Mark schemes must be read in conjunction with the question papers and the Report on the Examination. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session.

• CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the November 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses’.



IGCSE – NOVEMBER 2005 0620 1


Question Number

Key Question Number

Key

1 B 21 D

2 D 22 D

3 C 23 B

4 D 24 D

5 C 25 A

6 A 26 D

7 A 27 D

8 C 28 D

9 D 29 B

10 A 30 B

11 B 31 C

12 C 32 C

13 D 33 B

14 B 34 C

15 D 35 B

16 B 36 C

17 C 37 A

18 A 38 B

19 D 39 B

20 B 40 A




0620 CHEMISTRY

0620/02 Paper 2 (Core Theory)

Maximum mark 80





CIE is publishing the mark schemes for the November 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.





1 (a) (i) N [1] (ii) N/O/F/Cl/Br [1] (iii) Br [1] (iv) He/Ne/Ar/Kr [1] (v) C [1] (vi) He/C/N/O [1] (vii) N [1] (b) (i) light bulbs/lamps/other suitable uses [1] (ii) balloons/other suitable uses [1] (iii) in oxygen tents in hospitals/oxyacetylene welding/other suitable uses [1] (c) (i) 8 electrons in outer shell; all other electrons correct i.e. 2,8 [2] (ii) full outer shell/outer shell cannot gain or lose electrons/stable electronic configuration with 8 electrons in outer shell [1] TOTAL 13 2 (a) NaCl [1] (b) evaporation of the water [1] (c) 3rd box down ticked [1] (d) (aqueous) silver nitrate; white precipitate [2] (e) (i) calcium sulphate [1] (ii) 136 [1] (iii) 2H2O [1] (iv) hydration [1] (v) H2SO4; 2 [2] (vi) heat (constantly) given out when anhydrite reacts with water [1] (f) 4th box ticked [1] TOTAL 13




3 (a) suitable graduated apparatus for gas collection; flask + reactants + closed system; correct labels (at least 2) [3] (b) (i) substance which speeds up the rate of a reaction [1] (ii) X; slope or gradient greatest/produced most gas in named time interval below 70s [2] (iii) same amount of hydrogen peroxide used/all conditions kept the same [1] (iv) very high melting or boiling points/high densities/form coloured compounds/form ions with different charges owtte [2] (c) particles (of hydrogen peroxide) move faster; greater frequency of collisions [2] (d) (i) enzymes are from living things/enzymes can be denatured/enzymes specific for one reaction/enzymes are proteins [1] (ii) D [1] TOTAL 13 4 (a) 2 from calcium/magnesium/sodium;

they are metal oxides/oxides of (reactive) metals are basic [2]

(b) (i) nitrogen dioxide; sulphur dioxide [2] (ii) nitrogen dioxide: from car exhausts;

sulphur dioxide: from burning fossil fuels [2]

(c) (i) carbon dioxide [1]

(ii) high temperature (ALLOW: heat) NOT: catalysis on its own [1]

(d) (i) too reactive/above C in reactivity series owtte [1]

(ii) 2; CO2 [2]

(iii) removal of oxygen from a compound/addition of electrons ALLOW: addition of hydrogen [1] TOTAL 12




5 (a) methane [1]

(b) A and B [1] (c) (i) C [1]

(ii) correct displayed formula = 2 correct displayed formula but not O – H bond = 1 [2]

(iii) heated with steam; suitable catalyst [2]

(d) (i) D [1] (ii) bromine (water); decolourised [2] (e) (i) ethanoic acid [1]

(ii) litmus; goes red/pH paper or meter; below7/bubbles of gas when

added to a carbonate [2]

TOTAL 13 6 (a) aluminium oxide [1]

(b) ions must be free to move [1]

(c) (i) graphite/carbon [1]

(ii) to the cathode/negative electrode; Al ions are positive/positive ions are attracted to negative electrode [2]

(d) decreased; cryolite; electrical [3]

(e) (i) aluminum has a low density [1]

(ii) low(er) electrical conductivity [1] (iii) it is stronger (than aluminum) [1]

(iv) ceramic [1]

(f) (i) lightweight [1]

(ii) add sodium hydroxide; white ppt; soluble in excess [3] OR add aqueous ammonia; white ppt; insoluble in excess

TOTAL 16

GRAND TOTAL 80



MARK SCHEME for the October/November 2005 question paper



Examination.

• CIE will not enter into discussion or correspondence in connection with these mark schemes. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session. CIE is publishing the mark schemes for the October/November 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.



IGCSE – OCTOBER/NOVEMBER 2005 0620 3


Question 1 (a)(i) lattice [1] (ii) high melting point or high fixed points poor conductor as solid good conductor as liquid, accept either aqueous or molten hard soluble in water Any TWO [2] (b)(i) Mg2+ [1] (ii) N3– [1] (iii) Mg3N2 [1] (iv) opposite charges [1] Do NOT accept "attract" it is in the question accept electrostatic attraction as a phrase TOTAL = 7 Question 2 (a)(i) boiling [1] (ii) lower temperature or over temperature range or no plateau [1] (iii) direct continuation of E to F [1] (iv) close or touching far apart [2] fast and random [1] cannot move apart can move apart [2] (b)(i) calcium ethanoate + hydrogen [1] (ii) zinc oxide or hydroxide [1]

(c) CH3COOH + NaOH º CH3COONa + H2O [2]

reactants [1] products [1] TOTAL = 12




Question 3 (a)(i) because concentration of BiCl3 decreases [2] bismuth chloride used up ONLY [1] (ii) products are being formed or concentration of products [1] increases. Concentration mark given either (i) or (ii) (iii) reaction has come to equilibrium [1] rates equal or no change in concentration [1] (iv) equilibrium to left or favours backward reaction or equilibrium moves to use up hydrochloric acid [1] BiOCl used up or BiCl3 formed [1] (b)(i) No change in volume or same number of moles on [1] both sides (ii) move to right [1] Increase in pressure favour side with smaller volume or smaller number of moles (of gas) or moves to side that tends to reduce pressure [1] TOTAL = 10 Question 4 (a)(i) general molecular formula same functional group physical properties show trend — bp increase with n same chemical properties common methods of preparation any TWO [2] (ii) C8H17OH Mass of one mole = 130 (g) [2] if formula correct but mass wrong [1] (b) propan-1-ol or propan-2-ol [1] corresponding structural formula [1] name and formula must correspond for [2] if not ONLY [1] (c)(i) structural formula of isomer [1] (ii) carbon dioxide and water [1] pentene [1] pentanoic acid [1] TOTAL = 10




Question 5

(a)(i) 38p 38e 50n [1] 38p 38e 52n [1] 30p 28e 35n [1]

(ii) Same number of protons and different number of neutrons [1]

(iii) 8+ 2 [1]

(b)(i) heat zinc blende in air to form oxide [1] reduce oxide with carbon [1]

(ii) galvanising sacrificial protection alloys batteries roofing Any ONE [1]

(c)(i) hydrochloric acid [1]

(ii) Sr2+ + 2e = Sr [1] 2Cl

– – 2e = Cl2 [1]

or 2Cl– = Cl2 + 2e

(iii) hydrogen [1] and strontium hydroxide [1] [2]

(d)(i) zinc + water = zinc oxide + hydrogen [1] heat [1] steam [1] [2]

(ii) Sr + 2H2O = Sr(OH)2 + H2 [2] Not balanced [1] cold water [1]

TOTAL = 19

Question 6

(a)(i) moles of NiCO3 reacted = 0.08 [1] mass of nickel carbonate reacted = 9.52 g [1] mass of nickel carbonate unreacted = 2.48 g [1]

(ii) maximum number of moles of hydrated salt = 0.08 [1] maximum mass of salt = 0.08 x 281 = 22.48 g [1] percentage yield 10.4/22.48 x 100 = 46.3% [1]

(b)(i) sulphuric acid COND description of titration repeat without indicator or with carbon evaporation any TWO [3]

(ii) suitable reactants calcium chloride and sodium fluoride [1] COND upon correct reagents filter [1] wash and dry precipitate [1]

OR Accept synthesis calcium [1] fluorine [1] burn or heat [1] [3]

TOTAL = 12




Question 7 (a) from methane [1] and water [1] OR electrolysis [1] suitable electrolyte [1] OR alkane [1] cracking [1] [2] (b)(i) iron [1] (ii) lower temperature moves equilibrium to right [1] because forward reaction is exothermic [1] (c)(i) H—H [1] endothermic [1] endothermic [1] exothermic (ii) More heat given out than taken in [1] –2328 + 945 + 1308 = –75(kJ) [1] OR More heat given out bond forming than taken in bond breaking [2] Must mention bond breaking and forming [2] TOTAL = 10




0620 CHEMISTRY

0620/05 Practical Test maximum raw mark 40





CIE is publishing the mark schemes for the November 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.





1 Table of results reaction times completed [1] in seconds [1] increasing [1] [3] (a) Graph. Points correctly plotted [3], –1 for each incorrect straight line [1] [4] (b) fizzing/bubbling [1] slowed down [1] cleared [1] [3] (c) (i) Experiment 5 [1] (ii) strongest/more concentrated acid [1] more collisions [1] [3] (d) marble [1] chip visible [1] acid used up [1] [3] (e) (i) e.g. size of chips different [1] starting the timer [1] [2] (ii) measure mass of chips [1] time individual experiments [1] [2] [sub total 20] 2 (a) colourless/white [1] crystals [1] [2] (b) liquefies [1] condensation at top of tube [1] indicator paper goes red [1] then white [1] [4] (c) (i) white [1] precipitate [1] dissolves [1] [3] (ii) white [1] precipitate [1] clears [1] [3] (iii) no change/reaction [1] [1] (iv) no change/reaction [1] [1] (v) alkaline gas [1], ammonia named [2] [2] (d) not a sulphate or halide [1] [1] (e) aluminium [1] nitrate [1] hydrated or similar [1] [3] [sub total 20] [total 40]







• CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the November 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.





1 (a) boxes filled in correctly to show: measuring cylinder (1) spatula (1) beaker (1) [3] (b) blue [1] (c) heat (1) to crystallising point (1) [2] 2 (a) electrodes correctly labelled [1] (b) bubbles at positive/negative electrode (1) bulb lights up (1) [2] (c) lighted splint (1) pops (1) [2] 3 (a) pestle (1) and mortar (1) [2] (b) chlorophyll more soluble in ethanol or similar [1] (c) filtration [1] (d) chromatography (1), paper (1), add pigments (1), use of solvent (1) [4] 4 Table of results: volumes of gas correctly completed (21, 24, 39, 47 and 56) - 1 for each incorrect [3] (a) points correctly plotted in graph (3), - 1 for each incorrect straight line (1) [4] (b) experiment 2 (1) not on line (1) [2] (c) (i) experiment 5 (1) (ii) strongest/more concentrated acid (1) more collisions (1) [3] (d) marble chip visible (1) acid used up (1) [2]




(e) (i) e.g. size of chips different/starting the timer [1] (ii) measure mass of chips/time individual experiments [1] 5 (b) (i) white (1) precipitate (1) dissolves (1) [3] (ii) white (1) precipitate (1) insoluble (1) [3] (c) acid gas/named/hydrated salt [1] (d) not a sulphate (1) not a halide (1) [2] (e) ammonia [1] (f) nitrate (1) hydrated/water (1) [2] 6 (a) 2 arrows in correct positions (1) each [2] (b) bromine (water) (1) goes colourless (1) [2] (c) suck-back problem [2] 7 (a) soil sample + water (1) stir/heat (1) filter (1) add Universal Indicator (1) chart (1) [5] (b) more samples (1) different parts of field (1) [2] Total 60




0620 CHEMISTRY


Mark schemes must be read in conjunction with the question papers and the report on the examination. The grade thresholds for various grades are published in the report on the examination for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses.

• CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2006 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.



IGCSE - OCT/NOV 2006 0620 01

© UCLES 2006

Question Number

Key Question Number

Key

1 C 21 D

2 B 22 B

3 B 23 C

4 C 24 A

5 C 25 B

6 A 26 C

7 D 27 B

8 C 28 D

9 D 29 A

10 C 30 A

11 A 31 B

12 B 32 B

13 C 33 A

14 C 34 B

15 D 35 B

16 A 36 D

17 C 37 A

18 D 38 D

19 B 39 B

20 C 40 A




0620 CHEMISTRY


This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began.






IGCSE - OCT/NOV 2006 0620 02

© UCLES 2006

1 (a) C [1]

(b) (i) 2;2 (both needed) [1]

(ii) 2 from: floats on water/on surface; moves (on surface); forms a ball/melts; disappears/dissolves ALLOW: spits/explodes (at end of reaction) [2] NOT: reacts violently

(iii) blue; solution is alkaline/sodium hydroxide/ (NaOH) is alkaline [2] ALLOW: (solution) is basic/is a base

(iv) 2nd and 3rd boxes ticked (1 each) [2]

(c) faster/more reactive OWTTE (than potassium) [1]

(d) (i) atoms of same element/same number of protons with different number of neutrons/different mass numbers [1]

NOT: elements/compounds with different mass numbers

(ii) 11 [1]

(iii) 19 [1]

(iv) energy/nuclear fuel/nuclear power plants NOT: nuclear weapons/unqualified fuel [1]

[Total: 13]

2 (a) CO2 [1]

(b) (i) reduced; metal; endothermic [3]

(ii) carbon [1]

(iii) limewater; turns cloudy/milky/goes white [2]

(c) add(aqueous) sodium hydroxide; light blue ppt; insoluble in excess [3] OR add aqueous ammonia; light blue ppt; soluble in excess/giving dark blue solution

(d) (i) correct diagram (2,4) [1]

(ii) (period) 2 [1]

(e) (i) alkane(s) [1]

(ii) ethane [1]

[Total: 14]


IGCSE - OCT/NOV 2006 0620 02

© UCLES 2006

3 (a) ring around OH group only [1]

(b) unsaturated because it contains (C=C) double bonds (both points needed) [1]

(c) carbon dioxide; water [2]

(d) (i) condenser [1]

(ii) 100oC (unit needed) [1]

(iii) it is above the water/floats on water [1]

(e) (i) on the origin line and directly below the spots [1]

(ii) 4 [1]

(iii) beaker with paper placed correctly and solvent level below the origin line and both solvent and origin line labelled [1]

(iv) random movement of molecules/molecules move anywhere [1] NOT: molecules move from higher to lower concentration

(v) correct formula for ethanol showing all atoms and bonds ALLOW: OH group shown without bond [1]

(vi) 2nd and 4th boxes ticked [1]

[Total: 13]

4 (a) substance containing different atoms bonded/ joined etc [1]

(b) treating acid soils/making plaster/any other specific reasonable use NaCl; CaCO3; in blast furnace/for making iron/making lime/any other specific reasonable use; ammonium nitrate; N = 2, H = 4, O = 3; [6]

(c) 80 [1]

[Total: 8]

5 (a) it is (very) reactive/near top of reactivity series [1]

(b) gives off bubbles rapidly; dissolves quickly; [2]

(c) for cutting/welding/for oxyacetylene blow torch [1]

(d) (i) 2H2O [1]

(ii) neutralization [1]

(e) (i) burette [1]

(ii) starts alkaline/stated alkaline pH; pH decreases/to stated lower pH [2] NOT: becomes more acid

[Total: 9]


IGCSE - OCT/NOV 2006 0620 02

© UCLES 2006

6 (a) PbBr2 [1] (b) giant; ionic [2] (c) (i) B [1] (ii) platinum [1] (iii) ions can move/so it can conduct electricity NOT: ions are free [1] (iv) bromine; lead [2] (d) (i) Br2 [1] (ii) orange/brown/red-brown: NOT yellow [1] (iii) bromine is more reactive than iodine/bromine is higher in the activity series than

iodine (must be comparison) ALLOW: ideas about stronger bonding in NaBr [1] (e) (i) correct formula showing all atoms and bonds [1] (ii) D [1] [Total: 13] 7 (a) A + D (both needed); reason: high melting point/coloured chlorides/coloured compounds [2] NOT: properties of transition elements not shown in the table (b) iron sulphate [1] (c) idea of measuring volume of gas/amount of gas; in measuring cylinder/tube; idea of measuring (volume of gas) with time/time intervals; [3] (d) (i) doubling concentration doubles rate/rate proportional to concentration = 2

increasing concentration increases rate/speed = 1 [2] (ii) slower/decreases [1] (iii) slower/decreases [1] [Total: 10] [TOTAL: 80]




0620 CHEMISTRY








IGCSE - OCT/NOV 2006 0620 3

© UCLES 2006

1 (i) noble gas argon (ii) acidic oxide carbon dioxide (iii) can be polymerised ethene (iv) active component oxygen (v) treatment of water chlorine (vi) product of respiration carbon dioxide [TOTAL = 6] 2 More than required number of answers – [0] (i) A, B, D [1] (ii) D [1] (iii) F [1] (iv) C and E [1] (v) A [1] (vi) E [1] [TOTAL = 6] 3 (a) limestone or marble or chalk or coral or calcite or aragonite [1] (b) (i) 100 [1] 56 ignore units in both cases [1] (ii) 7.00kg is 1/8 of 56 [1] 1/8 of 100kg is 12.5kg [1] Give both marks for correct answer without explanation. Ignore missing units

but penalise wrong units (c) (i) Any reasonable explanation Plants prefer soil pH about 7 Plants do not grow (well) in acidic soils/plants grow better To increase crop yields Any ONE [1] Do NOT accept in acidic soils plants die (ii) With calcium carbonate, pH cannot go above 7 [1] It is not washed away by the rain/remains longer in the soil It is not absorbed by the plant [1] OR With calcium oxide, pH can go above 7 [1] It is washed away by the rain [1] (iii) Any correct use - making steel/iron, making cement, making glass, [1] disposing of acid wastes, removing sulphur dioxide from flue gases, (stone in) building, indigestion tablets, toothpaste, cosmetics etc [TOTAL = 9] 4 (a) (i) CH4 + 2O2 = CO2 + 2H2O [2] Not balanced [1] ONLY (ii) carbon monoxide is formed [1] COND it is poisonous [1] NOT incomplete combustion (b) Burns to form sulphur dioxide [1] Comment about acid rain/lung disease e.g. bronchitis [1]



© UCLES 2006

(c) (i) Transition elements/metals or d block elements [1] (ii) carbon monoxide is changed into carbon dioxide [1] hydrocarbons to carbon dioxide and water (by reacting with the oxygen) [1] [TOTAL = 9] 5 (a) (i) iron [1] (ii) advantage higher yield [1] explanation lower temperature favours the exothermic reaction (that is the forward reaction) [1] (b) (i) Sent over the catalyst again or used to make more ammonia [1] NOT just reused (ii) It has the highest boiling point [1] (c) (i) CO2 + 2NH3 = CO(NH2)2 + H2O [2] Not balanced [1] (ii) Any comment based on deficiency of PK/or ONLY provides Nitrogen as a

nutrient [1] NOT soil pH (d) Correct diagram for urea [3] one error ONLY [2] two errors ONLY [1] three errors 0 [TOTAL = 11] 6 (a)

copper iron sulphur

composition by mass/g

(4.80) (4.20) 4.8 [1]

number of moles of atoms

0.075 0.075 0.15 [1]

simplest mole ratio of atoms

1 1 2 [1]

[3] The empirical formula is CuFeS2 [1] (b) (i) impure copper/blister copper/boulder copper etc [1] (pure) copper [1] copper sulphate or nitrate or chloride or contains Cu

2+aq [1]

(ii) Cu

2+ + 2e

- = Cu [1]

(iii) Zinc [1] (c) Copper has delocalised electrons [1] In sulphur the electrons are localised or cannot move in the piece of sulphur [1] In copper there are layers of copper atoms/ions Which can slip [1] In sulphur there are no layers [1] [TOTAL = 13]



© UCLES 2006

7 (a) (i) greater initial slope or levels off later [1] Twice final volume [1] (ii) smaller slope [1] same final volume [1] (b) more particles in same volume/particles closer together [1] greater collision rate [1] molecules move faster [1] greater collision rate [1] OR molecules have more energy [1] so more will have sufficient energy to react [1] (c) (i) glucose [1] oxygen [1] (ii) chlorophyll [1] [TOTAL = 11] 8 (a) (i) biological catalyst [1] (ii) linkage ----O---- same unit as in glucose as on question paper that is rectangles [1] (iii) chromatography [1] (b) (i) --NHCO—linkage different units -NH and -CO on same monomer unit All three [2] two points [1] [2] (ii) amino acids [1] (c) (i) propanol + ethanoic acid = propyl ethanoate + water [2] reactants [1] products [1] (ii) ester linkage correct [1] rest of molecule correct [1] (iii) bromine water [1] fat 1 orange or yellow or brown to colourless [1] fat 2 remains orange or yellow or brown [1] Accept Potassium Manganate(VII) with corresponding colour changes (iv) soap or sodium salts (of carboxylic acids)/sodium stearate [1] alcohol/glycerol [1] [TOTAL = 15] [6+6+9+9+11+13+11+15 = 80]




0620 CHEMISTRY









© UCLES 2006

1 Table of results Experiments 1, 2 and 3

Initial and final temperature boxes correctly completed(2)

Comparable to Supervisor(2)

Observations

Zinc fizz/bubbles(1) colour of solution paler/brown(1) Iron colour of solution paler(1) brown/red residue(1) Magnesium lighted splint pops(1) [9] (a) (i) magnesium(1)

(ii) highest (temperature) difference(1)

bubbles given off (most) rapidly/ most vigorous reaction(1)

not reference to reactivity series [2]

(iii) hydrogen(1) [1]

Experiments 4 and 5

Magnesium and zinc temperature boxes correctly completed(1)

Comparable to Supervisor(2) [3]

(b) Graph points plotted correctly(2) smooth line graphs(1) labels(1) [4]

(c) temperature from graph(1) any indication on graph(1) [2]

sub total [22]

2 (a) reference to solid smaller/sublimate description e.g. white solid(1)

indicator paper turned blue(1) then red(1) [3]

(c) (i) colour(1) pH(1) eg green/orange <7 [2]

(ii) indicator/litmus turns blue(1) reference to smell(1) [2]

(iii) white(1) precipitate(1) [2]

(iv) white precipitate(1) [1]

(d) (ii) yellow(1) precipitate(1) [2]

(iii) yellow(1) precipitate(1) [2]

(e) ammonia(1) [1]

(f) ammonium(1) chloride(1) [2]

(g) iodide(1) [1]

sub total [18]

[Total for paper 40]




0620 CHEMISTRY









© UCLES 2006

1 (a) Boxes filled in correctly to show

tongs(1)

watch glass/evaporating basin/dish(1)

beaker(1) [3]

(b) oxidation/combustion/exothermic/redox(1) [1]

(c) > 7(1) [1]

2 (a) brown/orange(1) [1]

(b) oxygen used in rusting(1) not air [1]

(c) (1) = 17%/ 16.6 → 17%(1) 2 for correct answer [2]

(d) more rust/quicker to rust/water further up tube/tube fills up(1) [1]

3 table of results

all volumes correct (2) 0, 9, 35, 62, 81, 88, 89 [2]

-1 for any incorrect

(a) graph

points (2) S-shaped curve joining all points(1) [3]

(b) exothermic/displacement/oxidation/redox(1) [1]

(c) (i) slow at start/speeds up/slows down at end max 2 [2]

(ii) surface dirty owtte at start/then clean/calcium being used up/warms up

max 2 [2]

100150

25×



© UCLES 2006

4 table of results

(a) temperatures correctly completed(3) differences(1)

zinc 24 56 32

iron 25 41 16

magnesium 23 69 46

-1 for each incorrect [4]

(b) (i) magnesium(1) [1]

(ii) gas evolved rapidly/reacts(1) greatest (temperature) difference(1) [2]

(iii) hydrogen(1) [1]

(c) Table of results temperatures correct (6) [6]

Time /s zinc magnesium 0 24 26 10 27 54 20 29 62 30 33 67 40 37 68 50 40 67 60 43 65

(d) Graph. Points plotted correctly(2) - 1 for each incorrect

Smooth lines(1) labels(1) [4]

(e) temperature after 5s/ 25-26°C ± 0.5°C(1) indication on grid(1) [2]

(f) sketch line for Mg below powder Mg(1)

sketch line for iron powder below zinc/ any line below top curve(1) [2]

(g) prevent heat loss/insulation(1) [1]

(h) one improvement e.g. use a burette/pipette to measure solution/ lid(1) [1]

5 (a) (ii) red(1) litmus turns blue(1) reference to smell(1) max 2 [2]

(c) weak(1) acid(1) [2]

(d) ammonia(1) [1]

(e) ammonium chloride(1) [1]

(f) potassium iodide(1) [1]

6 (a) paint sample + water(1) filter(1) solid residue(1) max 2 [2]

(b) solid + organic solvent(1) add to paper(1)

chromatography(1) use of solvent(1) description of spots(1)

max 4 NB use of water = max 1 for chromatography [4]

(c) (i) apply paint, start timer(1) method of checking dry, note time(1)

no painting = 0 [2]

(ii) correct method(1) e.g. hair drier/wind/fan/increase temperature.

NOT catalyst. [1]



© UCLES 2006

[Total 60]




0620 CHEMISTRY






IGCSE – October/November 2007 0620 01

© UCLES 2007

Question Number

Key Question Number

Key

1 A 21 C

2 C 22 D

3 B 23 C

4 A 24 B

5 A 25 D

6 C 26 D

7 C 27 C

8 B 28 C

9 D 29 C

10 D 30 A

11 B 31 B

12 D 32 B

13 A 33 D

14 D 34 C

15 C 35 A

16 B 36 A

17 C 37 C

18 C 38 B

19 A 39 D

20 B 40 D




0620 CHEMISTRY









© UCLES 2007

1 (a) sulphur dioxide [1] ALLOW: SO2/sulphur/S (b) carbon dioxide [1] ALLOW: CO2

(c) carbon monoxide [1] ALLOW: CO (d) water [1] ALLOW: H2O (e) calcium oxide [1] ALLOW: CaO/calcium/Ca (f) calcium oxide and sodium oxide [1] ALLOW: correct formulae or calcium and sodium (g) both bonds shown by dot and cross [1] ALLOW: dot and cross anywhere along the bonding line (h) P2O3 [1] ALLOW: 2P2O3



© UCLES 2007

2 (a) (i) monomers [1] (ii) alkenes [1] (iii) contains (carbon-carbon) double bonds [1] ALLOW: can add on extra hydrogen substance containing hydrogen and carbon only [1] (iv) bromine water/acidified potassium permanganate [1] no reaction/stays orange/nothing [1] (bromine) decolourised/goes colourless [1] (b) addition/additional [1] ALLOW: ethene/alkene (c) (i) any two of: chloride/hydrogencarbonate/nitrate/sulphate [1] ALLOW: correct formulae (ii) calcium/Ca2+/Ca [1] (iii) 40 (mg) [1] (iv) chloride/Cl

– [1] (v) nitrate/NO3

– [1] (vi) e–/e [1] (d) 2nd box down ticked [1] (e) (i) condenser/condensing tube [1] (ii) beaker [1] (iii) it is different/boiling point (in flask) is higher/pure water is lower [1] (f) any two of: bacteria or soil particles are larger than gaps in limestone/ water particles are smaller than gaps in limestone/ particles/bacteria or soil (particles) are larger than water molecules idea of bacterial or soil particles trapped above the limestone/ idea of filtration [2] ALLOW: particles/bacteria or soil (particles) are larger than water molecules



© UCLES 2007

3 (a) aluminium – aircraft bodies; potassium – very soft; platinum – electrodes; iron – extracted from haematite; [4] (b) any two of: fizzing or bubbles/ iron disappears or dissolves/ solution becomes coloured/green [2] NOT: gets warm/iron changes colour/precipitate formed (c) (i) mixture; iron; harder/stronger/more brittle or other suitable comment [3] ALLOW: hard/strong (ii) any alloy e.g. brass/bronze [1] (iii) any two methods e.g. galvanising/painting/covering with oil/sacrificial protection (or description)/ plating with another metal [2] NOT: unspecified ‘coating’



© UCLES 2007

4 (a) increases (at first) ALLOW: becomes acidic; then decreases/becomes less acidic [2] NOT: reference to pH values/ends up alkaline

(b) (i) any two of: sweet is acidic/ saliva only produced gradually or saliva not present at first (so pH goes down at first)/ saliva neutralises the acid ALLOW: neutralises the sweet/ as more saliva produced more acid neutralised/ [2] (ii) neutralisation [1]

(c) (i) -OH group circled [1] (ii) carboxylic (acid) [1] (iii) CH3CO2H/CH3COOH/correct displayed formula [1] ALLOW: C2H4O2

(d) (i) gas given off/carbon dioxide given off [1] IGNORE: wrong gas (ii) filter funnel and filter paper; ALLOW: just filter paper cone calcium citrate/precipitate shown in funnel and filtrate below [2] (if no labels max 1 mark) (iii) to remove (excess) lemon juice [1] ALLOW: to remove impurities (iv) evaporate (off water)/boil off some of the water and leave [1] ALLOW: leave solution in warm place/on the windowsill NOT: ‘heat’ without suitable qualification (v) microorganisms [1]

5 (a) (i) removal of oxygen from compound/electron gain/decrease in oxidation number [1] ALLOW: addition of hydrogen (ii) copper [1] (iii) idea of electric circuit; bulb lights/meter gives reading [2] NOT: electrolysis/melt the substance to see if it conducts

(b) (i) hydrocarbons (in coal)/the coal [1] ALLOW: from the damp cotton wool (ii) close together/randomly arranged NOT: further apart than in a solid moving (from place to place/randomly)/random movement [2]



© UCLES 2007

6 (a) proton number/atomic number/number of + charges in nucleus [1] (b) they have the same (relative) atomic mass [1] (c) noble gases/group 0/group 8/group 18/rare gases [1] (d) any 3 differences e.g. no atomic numbers shown/ no relative atomic masses shown/ (Newlands’) groups are horizontal or periods are vertical/ no block for transition elements/ Co and Ni appear to be in with halogens or other similar discrepancies/ some elements not in correct order of molar masses/ more elements in modern table/ no man made elements/ any other suitable difference [3] (e) (i) layers slide over each other/layers flake off easily/forces between layers weak [1] NOT: weak forces between carbon atoms (without any further details) (ii) no weak bonds/only strong bonds [1] ALLOW: giant structure/lattice of covalent bonds 7 (a) methane water copper [1] (b) silver – conducts/yes; sodium chloride – soluble; sulphur – insoluble; copper sulphate – no; [4] (c) (i) graphite/platinum [1] (ii) chlorine/Cl2 NOT Cl; hydrogen/H2 NOT H [2] ALLOW: 1 mark for chlorine and hydrogen at incorrect electrodes (iii) anode [1] (iv) in solid ions cannot move/fixed in place; in aqueous solution ions move [2]




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© UCLES 2007

1 simple distillation [1] diffusion or fractional distillation [1] crystallisation [1] fractional distillation [1] filtration [1] NOTE As the candidate are selecting from a list, the above are the only acceptable

responses. [Total: 5]

2 (a) 23

11Na [1] 40

18Ar [1] 31

15P3– [1] for charge and [1] for symbol etc. [2]

27

13Al 3+ [1] for charge and [1] for symbol etc. [2]

ACCEPT +3 and –3 NOTE Only the above are to be awarded the mark

(b) particle B or 23

11Na or sodium [1] COND they have the same proton number or the same number of protons or the same atomic number [1] NOT the same number of electrons Accept same number of electrons and protons [Total: 8]

3 (a) Correct ratio MgBr2 or Mg 2Br [1] Accept anywhere in space IF formula suggests covalency then [1] only for MgBr2 or Mg 2Br correct charges Mg2+ and Br– [1] Do not be concerned about location of minus sign 8e around bromine [1] NOTE do not require correct coding – just 7 and 1 coded differently NOTE ignore electrons around magnesium

(b) (i) pattern or order or regular or repeat or alternate [1] COND positive and negative ions or atoms or molecules or particles [1] NOTE Accept a sketch that shows the above, that is particles arranged in a regular

way, e.g. any ionic compound such as sodium chloride (ii) Any reason from the list: [1] charges must balance or based on valencies or group II and group VII or 2e in outer level and 7e in outer level or magnesium loses 2 electrons and bromine gains 1 electron (per atom) (iii) reducing or reduction or reductant [1] lost electrons or given or donated electrons or transferred (to bromine) [1] reduced [1] gained or accepted electrons [1] [Total: 10]



© UCLES 2007

4 (a) (i) bleach for wood pulp or preserving food or sterilising or in wine making or as a refrigerant or in metallurgy or (liquid) sulphur dioxide is used in the petroleum industry or kill microbes(etc) or insecticide [1] (ii) (react with) oxygen or air [1] NOT burnt/burn in air/oxygen 450°C [1] vanadium oxide catalyst (if oxidation state given has to be correct) or platinum [1] If four conditions are given which include high pressure then MAX [2] High pressure is incorrect MAX 10 atm. (iii) ammonium sulphate or superphosphate [1] or potassium sulphate or magnesium sulphate (b) (i) vaporisation or boiling or evaporation [1] condensation or liquefaction [1] NOTE order in which changes are given is not important NOT liquid => gas => liquid (ii) to get maximum yield of zinc or reduce all zinc oxide [1] NOTE the above mark is awarded for why add excess carbon moves equilibrium to

right or to favours the products or removes CO2 from equilibrium [1] NOTE this mark is awarded for how does the addition of excess carbon give max

yield of zinc NOTE Allow any coherent explanation flexibly based on the above ideas EXAMPLES: moves equilibrium to right [1] because carbon dioxide removed [1] to get maximum yield of zinc [1] as equilibrium moves to right [1] NOT just to make CO from CO2 (c) (i) Zn2+ + 2e = Zn [1] (ii) 4OH– – 4e = O2 + 2H2O [2] or 4OH– = O2 + 2H2O + 4e or 2H2O = 4H+ + O2 + 4e or 2H2O – 4e = 4H+ + O2 oxygen as product [1] (iii) sulphuric acid [1] NOTE there are no alternative answers to the above (d) prevent iron from rusting NOT with galvanising or sacrificial protection making brass or making alloys NOT bronze electroplating or as an electrode in electrolysis cells roofing sacrificial protection coinage TWO uses [2] [Total: 15]



© UCLES 2007

5 (a) (i) equilibrium to left or many molecules and few ions or partially ionised or reverse reaction favoured [1] (ii) Water donates proton [1] methylamine accepts a proton [1] NOTE If hydrogen ion then ONLY [1] provided both are correct (b) less than 12 more than 7 [1] smaller concentration of hydroxide ions or partially dissociated or poor proton acceptor or poor H+ acceptor [1] NOT it is a weak base (c) (i) CH3NH2 + HCl = CH3NH3Cl [1] methylammonium chloride [1] NOTE the equation must be as written, the equation with sulphuric acid has been

given as guidance. (ii) brown precipitate [1] ACCEPT orange or red/brown or brick red or brown/red (iii) sodium hydroxide or any named strong base [1] [Total: 9] 6 (a) (i) heat (energy) [1] (ii) exothermic [1] (iii) C2H5OH + 3O2 = 2CO2 + 3H2O [2] For CO2 + H2O ONLY [1] (iv) plotting points correctly [1] straight line [1] between –2640 and –2700kJ/mol [1] NOTE minus sign needed (v) general (molecular) formula same functional group consecutive members differ by CH2 similar chemical properties or react same way NOT a comment about physical properties ANY TWO [2] (b) CH3- CH(OH)-CH3 [1] NOT C3H7OH propan-2-ol “2” is needed [1] NOTE the name and the formula must correspond for both marks accept full structural formula – all bonds shown correctly accept formulae of the ether NOT CH3- CH(HO)-CH3



© UCLES 2007

(c) (i) cracking heat (alkane) or (alkane) and catalyst NOTE thermal cracking or catalytic cracking [2] alkane = alkene + hydrogen ANY TWO [2] OR steam reforming CH4 + H2O = CO + 3H2 [2] or water/steam [1] catalyst or heat [1] (ii) combustion or burning [1] incomplete or insufficient oxygen/air [1] OR ACCEPT steam reforming as above [2] (iii) high pressure [1] COND forward reaction volume decrease or volume of reactants greater than that of products or fewer moles of gas on the right or fewer gas molecules on right [1] NOTE accept correct arguments about either reactants or products (d) (i) methyl ethanoate [1] (ii) propanoic acid or propanal [1] (iii) ethene [1] [Total: 20] 7 (a) (i) lower concentration [1] ACCEPT without reference to experiment 2 but higher concentration must be referred to expt 1 COND fewer collisions or lower rate of collision [1] (ii) powdered so larger surface area [1] COND so more collisions or higher rate of collisions [1] (iii) higher temperature particles move faster or more particles have enough energy to react or have more energy or more particles have Ea [1] COND collide more frequently or more particles have energy to react or more collisions result in a reaction [1] NOTE for conformity faster collisions = rate of collisions



© UCLES 2007

(b) (i) from origin [1] gradient decreases until = 0 [1] therefore has to be a curve (ii) mass of one mole of CaCO3 = 100 number of moles of CaCO3 = 0.3/100 = 0.003 [1] moles of HCl = 5/1000 x 1 = 0.005 [1] reagent in excess is CaCO3 [1] ecf from above would need 0.006 moles of HCl or hydrochloric acid only reacts with 0.0025 moles of CaCO3 [1] NOTE this mark needs to show recognition of the 1:2 ratio (iii) mark ecf to (ii), that is from moles of limiting reagent in (ii) moles of CO2 = 0.005 x 0.5 x 24 = 0.06 dm3 [1] NOT cm3 unless numerically correct. 60 cm3 Ignore other units NOTE If both number of moles integers then no ecf for (ii) and (iii) [Total: 13]




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© UCLES 2007

1 Table of results For all Experiments Initial temperature boxes correctly completed (1) Final temperature boxes correctly completed (1) Differences correctly completed (1) Each experiment comparable to Supervisor ± 3 °C, 4 × 1 = (4) [7] (a) rapid/fast/violent (1) bubbles/fizz (1) [2] (b) appropriate scale for y axis (1) 4 bars correctly drawn (2), –1 for incorrect bar, no labels = 1 [3] (c) compare candidates results (i) Experiment 1 (1) [1] (ii) Experiment 4 (1) [1] (d) correct reference to particle size/surface area (1) different chemicals used/calcium oxide is more reactive with hydrochloric acid than

calcium carbonate (1) [2] (e) hydrochloric acid (1) solid all gone at end of reaction (1) [2] (f) temperature changes would be smaller/less (1) larger volumes of acid (1) [2] [Total: 20]



© UCLES 2007

2 (a) liquid colour pH P red/pink 1-3 Q purple/blue 11-14 R yellow/orange/red 1-6 S red 1-3 Colours correct (1), compare supervisor’s pH values correct (1) [2] (b) (i) bubbles/fizz (1) lighted splint (1) pops (1) [3] (ii) Q no reaction/change (1) R bubbles/fizz S bubbles/fizz (1) [2] (c) bubbles/fizz (1) limewater (1) milky (1) [3] (d) white (1) precipitate (1) [2] (e) green (1) precipitate (1) [2] (f) hydrogen (1) [1] (g) carbon dioxide (1) [1] (h) hydrochloric acid/HCl (1) [1] (i) alkali (1) or sodium hydroxide (2) [2] (j) weak acid (1) [1] [Total: 20]




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© UCLES 2007

1 (a) (i) correct indication for crystals (1) (ii) correct indication of heat (1) no labels but correct position max 1 [2] (b) to cool/condense the water/gas/liquid (1) [1] (c) blue (1) to white/grey (1) [2] 2 (a) brown/orange/red-brown (1) [1] (b) (i) takes the place of oxygen owtte (1) not air [1] (ii) 16.6–17% (1) [1] (c) (i) formation of rust slower (1) [1] (ii) no effect (1) [1] 3 (a) So that all acid is used up/neutralised (1) [1] (b) filter (1) [1] (c) (i) no more solid/solute can dissolve (1) at that temperature (1) [2] (ii) use a glass rod to show crystals forming/observe crystals forming on edge of solution (1) [1] (d) to prevent breakdown of the crystals/not form powder/not lose water (1) [1]



© UCLES 2007

4 Table of results For all experiments Initial temperature boxes correctly completed 18, 26, 16, 22 and final temperature boxes correctly completed (3) –1 for each incorrect 19, 29, 21, 41 Differences correctly completed (1) [4] 1, 3, 5, 19 (a) bubbles/fizz (1) [1] (b) Appropriate scale for y-axis (1) 4 bars correctly drawn (2), –1 for incorrect bar [3] (c) (i) Experiment 1 (1) [1] (ii) Experiment 4 (1) [1] (d) correct reference to particle size/surface area (1) different chemicals used owtte (1) [2] (e) reason (1) for specified reagent (1) e.g. marble chips (1) visible at end of reaction (1) [2] (f) temperature changes would be smaller/less (1) larger volume of acid (1) [2]



© UCLES 2007

5 (a) (i) Q blue/purple (1) 11–14 (1) [2] (ii) Q no reaction/change (1) R bubbles/fizz (1) [2] (c) bubbles/fizz (1) limewater (1) milky (1) [3] (e) green (1) precipitate (1) [2] (f) hydrogen (1) [1] (g) carbon dioxide (1) [1] (h) hydrochloric acid/HCl (1) [1] (i) weak (1) acid (1) [2] 6 volumes correctly completed time/minutes volume/cm3

0 0

2 18

4 30

6 33

8 42

10 45

12 46 [3] (a) All points plotted correctly (2) –1 for any incorrect smooth line graph (1) [3] (b) (i) at 6 minutes (1) [1] (ii) 37/38 cm3 (1) [1] 7 same volume/mass of fuel/idea of fair test (1) initial temperature of water (1) burn/ignite fuel (1) record temperature of water (1) repeat (1) compare e.g. greatest temperature rise in specified time shows better fuel (1) [6]




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• CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for October/November 2008 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.




© UCLES 2008

Question Number

Key Question Number

Key

1 B 21 D

2 B 22 D

3 B 23 A

4 A 24 C

5 D 25 C

6 C 26 A

7 C 27 A

8 D 28 B

9 A 29 B

10 B 30 C

11 B 31 D

12 C 32 D

13 B 33 A

14 D 34 C

15 A 35 D

16 D 36 A

17 A 37 C

18 C 38 B

19 C 39 B

20 B 40 A




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© UCLES 2008

1 (a) metal; non-metal; non-metal; non-metal; non-metal; [5] ALLOW: named metal or non-metal or correct symbols (b) metallic character decreases (across the table)/metals on the left and non-metals on

the right [1] ALLOW: metals get less reactive (across the table)/metals conduct better across the

table) (c) (i) electrons shown in shells as 2,8,1 [1] ALLOW 2,8,1 (ii) + e/electron (on the right) [1] (d) soft; increase; lithium; basic; [4] [Total: 12] 2 (a) sulphur dioxide → combustion of fossil fuels containing sulphur; carbon monoxide → incomplete combustion of fossil fuels; ALLOW: carbon monoxide → car exhausts nitrogen oxides → car exhausts; [3] (b) (i) oxygen is added [1] ALLOW: electrons are lost (from sulphur dioxide) (ii) 21% [1] ALLOW 19-22% (iii) neutralisation [1] (iv) Any two of: crops remove nitrogen (or phosphorus or potassium) from soil/ nitrogen or essential elements etc. removed when crops harvested; fertilisers provide nitrogen or essential elements or nutrients or minerals/ fertilisers improve plant growth or yield; [2] (v) ammonium nitrate [1] NOT: ammonia nitrate/ammonium salt/nitrate salt [Total: 9]



© UCLES 2008

3 (a) (i) heating (calcium carbonate in a furnace) [1] (ii) CaCO3 → CaO + CO2 [1] (iii) neutralising (acid) soil/neutralising industrial waste [1] ALLOW: for making mortar/for making limewater NOT: for limewater (b) (i) thermometer; flask; measuring cylinder; [3] (ii) calcium carbonate + hydrochloric acid → calcium chloride + carbon dioxide + water (1 mark for correct reactants; 1 mark for correct products) [2] ALLOW: hydrogen chloride in place of hydrochloric acid (iii) 86s [1] ALLOW: between 81 and 90s (iv) slope of graph steeper and always above other line; graph flattens out at 80 cm3 gas; [2] (v) (speed) decreased/less/slower; (speed) increased/more/faster; [2] [Total: 13]



© UCLES 2008

4 (a) haematite (or any other correct ore) [1] NOT: iron oxide (b) (i) calcium carbonate/limestone/CaCO3 [1] (ii) C/just above the iron [1] (c) (i) 2C + O2 → 2CO 1 mark for O2; 1 mark for 2C and 2CO; [2] (ii) poisonous/toxic/kills you/deadly/suffocates you [1] NOT: harmful/causes breathing difficulties (d) 1st and 3rd boxes ticked [1] (e) Any two of: blast furnace can only be used for metals below zinc or carbon; aluminium is very reactive or high in the reactivity series or too reactive or higher then

iron in the reactivity series; carbon cannot remove oxygen from aluminium oxide/carbon cannot displace

aluminium; aluminium above carbon in reactivity series or more reactive than C = 2 marks too much heat required for carbon to remove oxygen from aluminium oxide = 2 marks [2] (f) (i) electrolysis [1] (ii) aircraft bodies/car bodies/(overhead) power cables/drinks cans/window frames etc. [1] [Total: 11]



© UCLES 2008

5 (a) (i) temperature of the water rises/heat given to the water/heat or energy given out/the thermometer reading goes up [1]

(ii) carbon dioxide + water (1 mark each) [2] (b) any two from coal/natural gas/wood/paraffin/any other suitable fuel containing carbon [2] ALLOW: named alcohols (except ethanol) NOT: alkenes/named alkenes/naphtha (c) OH/–OH [1] NOT: complete formula for ethanol (d) blue cobalt chloride (paper); turns pink or white/anhydrous copper sulphate; turns blue [2] (e) (i) painting/galvanising/covering with plastic/sacrificial protection/(electro)plating [1] ALLOW: oiling/greasing NOT: removing air/removing water (ii) contains water NOT: dissolves in water [1] (iii) Any two of: high boiling point or melting point; can act as catalyst; forms coloured compounds; high density; compounds can have variable oxidation states or have ions with different charges; [2] ALLOW: general metallic properties e.g. conducts electricity; conducts heat; ductile

etc. NOT: not very reactive [Total: 12]



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6 (a) Any two of; (group of similar organic) compounds with same chemical properties; (group of similar organic) compounds showing trend in physical properties; have same functional group; have same general formula; members differ by CH2 group; [2] ALLOW: can be made by same method (b) ethane; correct structure of ethane; [2] ALLOW: correct structure from incorrectly named alkane (c) 1st row correct structure of ethene; use e.g. for making plastics/ethanol etc.; [2] 2nd row correct structure of ethanoic acid; [1] 3rd row C2H4Br2; [1] 4th row methane; fuel; [2] (d) 188 [1] ALLOW: error carried forward from incorrect structure in the table [Total: 11]



© UCLES 2008

7 (a) (i) ions cannot move in solid; ions move when molten; [2] (ii) calcium has atoms/particles closely packed together/regularly arranged/strong

forces between particles/particles can’t move; ALLOW: calcium has high boiling point (because of strong forces between

particles) chlorine has molecules/particles randomly arranged/far apart/particles can move

easily (from place to place); [2] ALLOW: chlorine has low boiling point (because of weak forces between particles) (b) (i) chlorine; calcium; [2] ALLOW: For 1 mark: calcium and chlorine the wrong way round NOT: chloride/chloride ions (ii) graphite/carbon [1] (iii) to prevent it from reacting with the air/oxygen [1] ALLOW: does not react/prevents (other) reactions (with calcium) (iv) any noble gas [1] ALLOW: nitrogen (c) with sodium hydroxide white precipitate; insoluble in excess; [2] with ammonia no precipitate/(very slight) white precipitate [1] ALLOW: no reaction/no change [Total: 12]




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© UCLES 2008

1 red litmus paper blue [1] OR white fumes/smoke with HCl (g) or (aq) chlorine [1] “pop” with a lighted splint or burn with a pop or goes pop and extinguishes flame [1] NOT glowing splint oxygen [1] carbon dioxide [1] ACCEPT correct formulae [Total: 5] 2 (a) 3Na : 1N correct ratio [1] correct charges [1] 8e around N [1] if no symbols then must have correct key if covalent only mark 1 ignore electrons around sodium if the response includes both a correct and an incorrect answer do not select correct one, mark = [0] (b) (i) positive ions or cations [1] NOT atoms or cores or nuclei layers or lattice or regular pattern [1] delocalised or free or mobile electrons or sea [1] OR positive ions or cations [1] NOT atoms or cores or nuclei attraction between ions and electrons [1] delocalised or free or mobile electrons or sea [1] the attraction/electrostatic bonding must be between ions and delocalised electrons, between cations and anions does not score ACCEPT bond if qualified - electrostatic bond, etc. if molecular or molecules then cannot score cation mark (ii) delocalised/free/mobile electrons or electrons can move [1] layers or ions or atoms or particles [1] NB more flexible than 2(b)(i) can slip or move past each other or bonding non-directional [1]

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(c) (i) tetrahedral [1] 1Si : 4O bonded/surrounded, etc. [1] 1O : 2 Si [1] NOT molecules of oxygen, etc. NOT intermolecular forces ONLY tetrahedral can score for either of the above Despite what the question states, ACCEPT a clear accurate diagram which shows the

above three points. (ii) hard high mp or bp colourless (NOT clear) or shiny or translucent non/poor conductor (of electricity) brittle insoluble any TWO [2] NOT crystalline or strong [Total: 14] 3 (a) (i) water or moisture ACCEPT salty water [1] air or oxygen [1] (ii) galvanising or coat with zinc tin plate

chromium plate nickel plate cobalt plate copper plate cover with aluminium

anodic protection or sacrificial protection cathodic protection cover with plastic alloying (ignore any named metal) any TWO [2] NOT just plate or electroplate need electroplate with suitable metal NOT oil ACCEPT both galvanising and sacrificial protection (b) (i) hydrogen or carbon or carbon monoxide or methane or more reactive metal NOT Group I [1] (ii) any correct equation [2] only error not balanced [1]

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© UCLES 2008

(c) (i) 196 [1] (ii) 112/196 × 100 [1] = 57(.1)% ACCEPT 57 to nearest whole number [1] mark e.c.f. to (c)(i) provided percentage not greater than 100% ONLY ACCEPT 112/answer (c)(i) × 100 otherwise [0] (d) (i) forms carbon dioxide/carbon monoxide (which escapes) [1] (ii) forms silicon(IV) oxide or silicon oxide or silica [1] OR CaO reacts with SiO2 to form slag or calcium silicate [1] ignore an incorrect formula if a correct name “slag” given NOT Si + O2 + CaO form slag, this gains mark for slag only [Total: 13] 4 (a) (i) C6H5COOH or C6H5CO2H [1] NOT C7H6O2 /C6H6COO (ii) sodium hydroxide + benzoic acid = sodium benzoate + water [1] correct spelling needed NOT benzenoate ACCEPT correct symbol equation (iii) sodium carbonate or oxide or hydrogencarbonate any TWO [2] NOT Na (b) (i) 7.7% [1] (ii) for any number: equal number ratio [2] for example 1:1 or 6:6 (iii) empirical formula is CH [1] molecular formula is C6H6 [1] no e.c.f., award of marks not dependent on (ii) (c) (i) C6H8O6 [1] (ii) carbon – carbon double bond or alkene [1] alcohol or hydroxyl or hydroxy [1] NOT hydroxide hydroxide and alcohol = 0 [Total: 12]

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© UCLES 2008

5 (a) (i) 2H+ + 2e � H2 [1] (ii) 2Cl

– – 2e � Cl2 or 2Cl – � Cl2 + 2e [1]

(iii) Na+ and OH– are left [1] OR Cl

– removed OH– left NB ions by name or formula essential NOT any reaction of Na or Na+ NOT Na+ and OH– combine (b) (i) sterilise/disinfect water or kill microbes/germs bacteria, etc. [1] NOT just to make it safe to drink or purify it or clean it treat above as neutral they do not negate a correct response (ii) ammonia or methanol or hydrogen chloride or margarine [1] NOT nylon (iii) fat or lipid or triester or named fat or glyceryl stearate [1] or vegetable oil heat [1] [Total: 7] 6 (a) (i)

aqueous solution

tin Sn

manganese Mn

silver Ag

zinc Zn

tin(II) nitrate R NR R

manganese(II) nitrate NR NR NR

silver(I) nitrate R R R

zinc nitrate NR R NR

[1] for each row [3] ignore anything written in blank space (ii) Sn + 2Ag+ � Sn2+ + 2Ag [2] all species correct [1] accept equation with Sn4+ (iii) Mn to Mn2+ need both species [1] electron loss or oxidation number increases [1] (iv) covered with oxide layer [1] makes it unreactive or protects or aluminium oxide unreactive [1] (b) (i) potassium has one valency electron [1] or loses one electron calcium has two valency electrons or loses two electrons [1] (ii) potassium hydroxide � no reaction [1] calcium hydroxide � calcium oxide and water [1] ACCEPT metal oxide

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© UCLES 2008

(iii) 2KNO3 � 2KNO2 + O2 [2] [1] for formula of either product 2Ca(NO3)2 � 2CaO + 4NO2 + O2 [2] [1] for formulae of any TWO products [Total: 17] 7 (a) (i) 35 cm3 [1] 40 cm3 [1] (ii) forms carbon monoxide [1] poisonous or toxic or lethal or prevents blood carrying oxygen or effect on haemoglobin [1] NOT just harmful (b) (i) chlorobutane or butyl chloride [1] number not required but if given must be 1, it must be in correct position (ii) light or UVor 200°C or lead tetraethyl [1] (iii) any correct equation for example 2-chlorobutane or dichlorobutane [1] (c) (i) correct repeat unit [1] COND continuation [1] -(CH(CH3)-CH2)- (ii) butan-1-ol or butan-2-ol or butanol [1] if number given then formula must correspond for second mark and number must be in

correct position structural formula of above [1] CH3-CH2-CH2-CH2OH or CH3-CH(OH)-CH2-CH3 NOT C4H9OH if first mark not awarded then either formula will gain mark [1] ACCEPT either formula for “butanol” (iii) CH3-CH(Cl)-CH3 or CH3-CH2-CH2-Cl [1]

NOT C3H7Cl response must not include HCl if equation given look at RHS only [Total: 12]

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© UCLES 2008

1 ammonia [1] chlorine [1] “pop” with a lighted splint or burn with a pop or goes pop and extinguishes flame [1] NOT glowing splint relights a glowing splint [1] turns limewater milky/cloudy/chalky/white [1] ACCEPT correct formulae [Total: 5] 2 (a) 2Na : 1S correct ratio [1] correct charges [1] 8e around S [1] if no symbols then must have correct key if covalent only mark 1 ignore electrons around sodium if the response includes both a correct and an incorrect answer do not select correct one, mark = [0] (b) (i) positive ions or cations [1] NOT atoms or cores or nuclei layers or lattice or regular pattern [1] delocalised or free or mobile electrons or sea [1] OR positive ions or cations [1] NOT atoms or cores or nuclei attraction between ions and electrons [1] delocalised or free or mobile electrons or sea [1] the attraction/electrostatic bonding must be between ions and delocalised electrons, between cations and anions does not score ACCEPT bond if qualified e.g. electrostatic bond, etc. if moles or molecular cannot score cation mark (ii) delocalised/free/mobile electrons or electrons can move [1] layers or ions or atoms or particles [1] NB more flexible than 2(b)(i) can slip or move past each other or bonding non-directional [1]

maigna




© UCLES 2008

(c) (i) tetrahedral [1] 1Si : 4O bonded/surrounded, etc. [1] 1O : 2 Si [1] NOT molecules of oxygen, etc. NOT intermolecular forces ONLY tetrahedral can score for either of the above Despite what the question states, ACCEPT a clear accurate diagram which shows the

above three points. (ii) hard high melting point or boiling point colourless (NOT clear) or shiny or translucent non/poor conductor (of electricity) brittle insoluble any TWO [2] NOT crystalline or strong [Total: 14] 3 (a) (i) water or moisture ACCEPT salty water [1] air or oxygen [1] (ii) galvanising or coat with zinc tin plate

chromium plate nickel plate cobalt plate copper plate cover with aluminium

anodic protection or sacrificial protection cathodic protection cover with plastic alloying (ignore any named metal) any TWO [2] NOT just plate or electroplate need electroplate with suitable metal NOT oil ACCEPT both galvanising and sacrificial protection (b) (i) hydrogen or carbon or carbon monoxide or methane or more reactive metal NOT Group I [1] (ii) any correct equation [2] only error not balanced [1]

maigna




© UCLES 2008

(c) (i) 196 [1] (ii) 36/196 × 100 [1] = 18(.4)% ACCEPT 18 to nearest whole number [1] mark e.c.f. to (c)(i) provided percentage not greater than 100% ONLY ACCEPT 36/answer (c)(i) × 100 otherwise [0] (d) (i) forms carbon dioxide/carbon monoxide (which escapes) [1] (ii) forms silicon(IV) oxide or silicon oxide or silica [1] OR CaO reacts with SiO2 to form slag or calcium silicate [1] ignore an incorrect formula if a correct name given NOT Si + O2 + CaO form slag [Total: 13] 4 (a) (i) C6H5COOH or C6H5CO2H [1] NOT C7H6O2 /C6H6COO (ii) sodium hydroxide + benzoic acid = sodium benzoate + water [1] correct spelling needed NOT benzenoate ACCEPT correct symbol equation (iii) sodium carbonate or oxide or hydrogencarbonate any TWO [2] NOT Na (b) (i) 7.7% [1] (ii) for any number: equal number ratio [2] for example 1:1 or 6:6 (iii) empirical formula is CH [1] molecular formula is C6H6 [1] no e.c.f., award of marks not dependent on (ii) (c) (i) C6H8O6 [1] (ii) carbon – carbon double bond or alkene [1] alcohol or hydroxyl or hydroxy [1] NOT hydroxide hydroxide and alcohol = 0 [Total: 12]

maigna




© UCLES 2008

5 (a) (i) 2H+ + 2e � H2 [1] (ii) 2Cl

– – 2e � Cl2 or 2Cl – � Cl2 + 2e [1]

(iii) Na+ and OH– are left [1] OR Cl

– removed OH– left NB ions by name or formula essential NOT any reaction of Na or Na+ NOT Na+ and OH– combine (b) (i) sterilise/disinfect water or kill microbes/germs bacteria, etc. [1] NOT just to make it safe to drink or purify it or clean it treat above as neutral they do not negate a correct response (ii) ammonia or methanol or hydrogen chloride or margarine [1] NOT nylon (iii) ester or triester or lipid [1] hydrolysis or saponification [1] [Total: 7] 6 (a) (i)

aqueous solution

tin Sn

manganese Mn

silver Ag

zinc Zn

tin(II) nitrate R NR R

manganese(II) nitrate NR NR NR

silver(I) nitrate R R R

zinc nitrate NR R NR

[1] for each row [3] ignore anything written in blank space (ii) Zn + 2AgNO3 � Zn(NO3)2 + 2Ag [2] all species correct [1] accept correct ionic equation Zn + 2Ag+ � Zn2+ + 2Ag [2] (iii) Sn2+ must be made clear that the oxidant is Sn2+ not Sn [1] it gains electrons or oxidation number decreases or it is reduced [1] reason must relate to an oxidant NB not dependent on identifying Sn2+ (iv) covered with oxide layer [1] makes it unreactive or protects or aluminium oxide unreactive [1]

maigna




© UCLES 2008

(b) (i) potassium has one valency electron [1] or loses one electron calcium has two valency electrons or loses two electrons [1]

(ii) potassium hydroxide � no reaction [1] calcium hydroxide � calcium oxide and water [1] ACCEPT metal oxide (iii) 2KNO3 � 2KNO2 + O2 [2] [1] for formula of either product

2Ca(NO3)2 � 2CaO + 4NO2 + O2 [2] [1] for formulae of any TWO products

[Total: 17]

7 (a) (i) 20 cm3 [1] 80 cm3 [1] (ii) forms carbon monoxide [1] poisonous or toxic or lethal or prevents blood carrying oxygen or effect on haemoglobin [1] NOT just harmful, etc. (b) (i) chlorobutane or butyl chloride [1] number not required but if given must be 1, it must be in correct position (ii) light or UV or 200 °C or lead tetraethyl [1] (iii) any correct equation for example 2-chlorobutane or dichlorobutane must include HCl [1]

(c) (i) correct repeat unit [1] COND continuation [1] –(CH(CH3)–CH2)– (ii) propan-1-ol or propan-2-ol or propanol [1] if number given then formula must correspond for second mark. number must be in correct position structural formula of above [1] CH3–CH2–CH2–OH or CH3–CH(OH)–CH3 NOT C3H7OH if first mark not awarded then either formula will gain mark [1]. accept either formula for “propanol” in (i) NB On scoris both marks entered together not as [1] and [1] separately (iii) CH3–CH2–CH2–CH2–Cl or CH3–CH2–CH(Cl)–CH3 [1] NOT C4H9Cl if equation given look at RHS only response must not include HCl

[Total: 12]

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0620 CHEMISTRY









© UCLES 2008

1 Experiment 5 observations rapid/vigorous o.w.t.t.e (1) bubbles/fizz (1) blue precipitate (1) [max 2] Table of results initial boxes correctly completed (1) final boxes correctly completed (1) differences correctly completed (1) signs correct (1) comparable to Supervisor’s results (1) [5] (a) all 4 bars correctly drawn (3), –1 for each incorrect labelled (1) [4] (b) (i) solid A/Experiment 1 (1) [1] (ii) temperature increased/heat/energy given out (1) [1] (c) Experiment 3/solid C or from results (1) [1] (d) (i) double the value or 2 × value from table (1) [1] e.c.f. applies (ii) half the value or half the value from table (1) [1] (iii) more/larger volume of water (1) twice as much (for solid to dissolve in) o.w.t.t.e. (1) [2] (e) acid present (1) carbonate present (1) carbon dioxide (1) [max 2] [Total: 20] 2 (a) solution K blue/green solution L yellow/orange/brown (1) [1] (b) check pHs from Supervisor’s results pH of solution K 1–6 pH of solution L 1–6 (1) [1] tests on solution K (c) (i) blue (1) precipitate (1) [2] (ii) deep/royal blue (1) solution/precipitate dissolves (1) [2] (iii) no reaction/change/nothing (1) not lighter [1] (iv) white (1) precipitate (1) [2]



© UCLES 2008

tests on solution L (d) (i) (rusty) brown (1) precipitate (1) [2] (ii) brown precipitate (1) not red [1] (iii) no reaction/change/nothing (1) [1] (iv) white (1) precipitate (1) not lighter/paler [2] (e) acidic (1) [1] (f) chloride/ Cl

– (1) [1] (g) (i) copper (1) [1] (ii) iron (1) (III) (1) [2] [Total: 20] [Total for paper: 40]




0620 CHEMISTRY









© UCLES 2008

1 (a) mortar (1) stirrer/(glass) rod (1) not metal rod or thermometer funnel (1) not filter or filter paper [3] (b) (i) water [1] (ii) origin correctly labelled on diagram i.e. at dot [1] (c) two spots/dots at different levels in vertical line [1] allow three spots if one is origin [Total: 6]

2 (a) carbon/graphite/any unreactive metal e.g. platinum/nickel [1] (b) lighted splint (1) pops (1) [2] (c) gas dissolves (in the solution) o.w.t.t.e [1] (d) alkali/(sodium) hydroxide (1) chlorine/bleach (1) not chloride or chlorine ions [2] [Total: 6]

3 (a) heat indicated in wrong position (1) no water in the trough (and collection tube) (1) [2] (b) bromine/iodine (water) (1) turns colourless (1) not clear [2] [Total: 4]

4 (a) Table of results Initial boxes correctly completed (1) 24

26 21 29

Final boxes correctly completed (1) 27

22 11 23

Differences correctly completed (1) +3 signs correct (1)

-4 -10 -6 [4]



© UCLES 2008

(b) all 4 bars correctly drawn (3), –1 for each incorrect labelled (1) [4] (c) (i) solid A/Experiment 1 [1] (ii) temperature increased/heat given out [1] (d) Experiment 3 [1] (e) (i) double the value or (–)8°C e.c.f. [1] (ii) half the value or (–)3°C e.c.f. [1] (iii) more/larger volume of water (1) twice as much (1) for solid to dissolve in [2] (f) acid present (1) carbonate present (1) carbon dioxide (1) [max 2] [Total: 17] 5 (a) solution K blue/green not precipitate [1] (c) tests on solution K (i) blue (1) precipitate (1) [2] (ii) blue precipitate [1] deep/royal (1) blue solution or precipitate dissolves (1) [2] (iii) no reaction/change/nothing [1] (iv) white precipitate [1] (d) tests on solution L (iii) no reaction/change/nothing [1] (iv) white precipitate [1] (e) acids [1] (f) iron (1) (III) (1) or Fe3+ (2) ignore anions [2] [Total: 13]



© UCLES 2008

6 (a) Points plotted correctly (3), –1 for each incorrect smooth curve (1) not a straight line [4]

(b) 47±1 or reading from graph (1) curve extrapolated on grid (1) [2] (c) solid/crystals form owtte (1) 20g (1) [2] not solubility decreases [Total: 8] 7 (a) heat/warm the acid (1) add excess oxide or description of no more solid reacting (1) filter/decant (1) [3] (b) heat qualified e.g. to crystallising point or description of e.g. using glass rod/leave it to

evaporate (1) cool to form crystals (1) filter off crystals (1) method of drying crystals e.g. pressed filter papers/oven at low temperature (1) [max 3] [Total: 6] [Total for paper: 60]





0620 CHEMISTRY







© UCLES 2009

Question Number

Key Question Number

Key

1 A 21 D

2 C 22 B

3 D 23 C

4 A 24 A

5 C 25 C

6 C 26 C

7 A 27 C

8 B 28 B

9 C 29 B

10 C 30 B

11 B 31 B

12 D 32 A

13 D 33 C

14 B 34 A

15 A 35 C

16 D 36 D

17 C 37 B

18 D 38 D

19 B 39 B

20 A 40 C





0620 ACCOUNTING







© UCLES 2009

Question Number

Key Question Number

Key

1 D 21 D

2 A 22 C

3 C 23 B

4 C 24 C

5 A 25 A

6 B 26 B

7 A 27 C

8 C 28 B

9 C 29 B

10 C 30 C

11 B 31 B

12 B 32 C

13 D 33 A

14 D 34 C

15 D 35 D

16 A 36 A

17 B 37 B

18 C 38 D

19 D 39 B

20 A 40 C





0620 CHEMISTRY








© UCLES 2009

1 (a) bromine and fluorine / Br and F [1] (b) krypton / Kr [1] (c) nitrogen and oxygen / N and O [1] (d) 175 [1] (e) (i) basic ALLOW: metallic [1] (ii) (burning) fossil fuels / fuels containing sulfur / volcanoes ; [1] effect of SO2 on environment e.g. destroys trees / kill plants / kills animals or plants in

lakes or rivers / chemical erosion of (limestone) buildings / corrosion of metals ; ALLOW: difficulty in breathing NOT: kills plants / animal in seas / kills marine life [1] (iii) any three of: starts off high pH / pH above 7 / named pH above 7 / alkaline (pH) ; as acid added pH goes down ; neutralises / neutralisation / neutral / pH 7 ; pH ends up below 7 / named pH below 7 / acid (pH) ; [3] (iv) universal indicator paper / pH meter [1] (v) potassium nitrate ALLOW: KNO3 [1] 2 (a) compound: top box ; element: 2nd box ; ion: 5th box ; molecule: 4th box ; [4] (b) air + steel / first and last boxes ticked [1]



© UCLES 2009

(c) (i) any four of: nucleus or particles on inside and electrons on outside ; nucleus labelled ; electrons on outside labelled ; ALLOW: e for label two electrons ; protons + neutrons in nucleus + labels ; ALLOW: p for proton and n for neutron IGNORE: incorrect number of neutrons two protons ; [4] (ii) balloons / (arc) welding / (advertising) lights / growing Si or Ge crystals / making Ti or Zr /

coolant (in nuclear reactors) / wind tunnels / for divers [1] NOT: as an inert gas / in (hot) air balloons / in bulbs (iii) helium unreactive / second box down ticked [1] 3 (a) structure of ethanol with all atoms and bonds shown ALLOW: OH in place of O – H [1] (b) (i) exothermic [1] (ii) 16.2 (g) [1]

(iii) 2 (CO2) + 3 (H2O) [1] (c) any two of: (very) high melting / boiling points ; (very) high density ; ALLOW: harder form coloured compounds ; NOT: they are coloured variable oxidation numbers / can form more than one type of ion / variable valency / form complex ions ; are (good) catalysts ; ALLOW: chemical differences e.g. do not react with cold water [2]



© UCLES 2009

(d) (i) any two of: bubbles / effervescence ; copper carbonate / solid dissolves ; solution becomes coloured / solution goes green / change of colour ; NOT: wrong colour [2 (ii) aqueous / dissolved in water [1] (e) polymer ; addition ; monomers ; [3] 4 (a) any two physical properties of group I metal e.g. (fairly) low melting boiling point (for a metal) ; solid ; conducts heat or conducts electricity ; malleable ; soft ; ALLOW: ductile / shiny (when cut) NOT: hard / sonorous [2] (b) 1 [1] (c) (i) atoms of same element / same proton number with different numbers of neutrons /

different number of nucleons [1] (ii) 78 [1] (d) boiling point 500 – 680 (actual = 669) ; [1] reactivity: any idea of faster than rubidium e.g. explosion / very violent spitting ; ALLOW: more reactive / increased reaction [1] (e) CsCl [1] (f) pH 7 [1] (g) (aqueous) silver nitrate / aqueous lead nitrate ; [1] white precipitate ; (result conditional on correct reagent) [1]



© UCLES 2009

5 (a) double bond(s) ringed [1] (b) C10H16 [1] (c) red-brown / brown ; [1] to colourless / loses its colour ; NOT: becomes discoloured [1] (d) (i) A thermometer ; B condenser ; C measuring cylinder ; NOT: measuring tube [3] (ii) arrangement: random ; ALLOW: far apart [1] movement: random / rapid / move everywhere ; [1] (e) (i) idea of oxygen not in excess / carbon monoxide formed (instead of carbon dioxide) ALLOW: doesn’t burn completely / doesn’t burn as much as it could ALLOW: carbon or soot formed (instead of carbon dioxide) [1] (ii) toxic / kills you / poisonous / asphyxiation / suffocation NOT: harmful [1] (f) (i) A [1] (ii) C [1] (iii) B [1] 6 (a) decomposition [1] (b) ions must be able to move NOT: charges must be able to move REJECT: ions and electrons move = 0 [1] (c) lower melting point of the electrolyte ALLOW: helps dissolve the aluminium oxide [1] (d) B [1]

(e) anode: oxygen ; [1] cathode: aluminium ; (both aluminium and oxygen but at wrong electrodes = 1) [1]



© UCLES 2009

(f) oxygen reacts with them / oxygen reacts with carbon ; [1] ‘burns’ them away / carbon dioxide formed / gas formed ; ALLOW: the electrodes get used up [1]

(g) 3 [1] (h) aircraft body / car body / saucepans/ electricity cables / food containers / window frames /

cooking foil / other suitable uses NOT: alloys unqualified [1] 7 (a) both parts required for each mark A: yes – air and water present ; [1] B: no – no water / there is only air ; [1] C: no – coating protects / zinc protects (from air and water) / zinc corrodes instead / zinc is a sacrificial metal ; [1] (b) any three of: oxygen blown into molten iron ; to oxidise sulphur / carbon / phsophorus / silicon ; basic oxides / CaO / MgO added ; react with phosphorus and silicon ; (P and Si) removed as slag / slag formed ; [3] (c) chemical plant / surgical instruments / cutlery [1] (d) O removed (from iron oxide) / oxidation number (of iron) decreased [1] (e) iron(II) oxide + hydrochloric acid → iron chloride + water (1 for correct reactants, 1 for correct products) [2]





0620 CHEMISTRY








© UCLES 2009

GENERAL INSTRUCTIONS FOR MARKING

• Error carried forward may be allowed in calculations. This will be discussed in the mark scheme. This is not applied when the candidate has inserted incorrect integers or when the answer is physically impossible.

• COND the award of this/these mark(s) is conditional upon a previous mark being awarded. Example – Is the reaction exothermic or endothermic? Give a reason for your choice. Mark scheme exothermic [1] COND a correct reason given [1]. This mark can only be awarded if the candidate has

recognised that the reaction is exothermic.




• In the mark scheme if a word or phrase is underlined it (or an equivalent) is required for the award of the mark.


• OR designates alternative and independent ways of gaining the marks for the question. or indicates different ways of gaining the same mark.

• Unusual responses which include correct Chemistry which answer the question should always be rewarded – even if they are not mentioned in the marking scheme.



© UCLES 2009

1 (a) (i) argon or krypton or helium [1] Accept xenon and radon even though percentages are very small NOT hydrogen (ii) water and carbon dioxide [2] (b) (i) sulfur dioxide or lead compounds or CFCs or methane or particulates or unburnt hydrocarbons or ozone etc. [1] (ii) incomplete combustion [1] of a fossil fuel or a named fuel or a fuel that contains carbon [1] (iii) at high temperature or inside engine [1] nitrogen and oxygen (from the air) react [1] (iv) it changes carbon monoxide to carbon dioxide [1] oxides of nitrogen to nitrogen [1] OR symbol or word equation of the type: 2NO + 2CO → CO2 + N2 [2] OR a redox explanation – the oxides of nitrogen oxidise carbon monoxide to carbon

dioxide, [1] they are reduced to nitrogen [1] OR 2NO → N2 + O2 [1] 2CO + O2 → 2CO2 [1] [Total: 10] 2 (a) pH < 7 [1] example [1] pH > 7 [1] example [1] NOT amphoteric oxides Be, Al, Zn, Pb, Sn etc pH = 7 [1] example H2O, CO, NO [1] the two marks are not linked, mark each independently NOT amphoteric oxides Be, Al, Zn, Pb, Sn etc. (b) (i) shows both basic and acidic properties [1] (ii) a named strong acid [1] a named alkali [1] [Total: 9]



© UCLES 2009

3 (a) (i) heat or roast or burn in air [1] need both points for mark (ii) ZnO + C → Zn + CO [2] or 2ZnO + C → 2Zn + CO2 unbalanced ONLY [1] (b) zinc is more reactive [1] it loses electrons and forms ions in preference to iron [1] zinc corrodes not iron [1] NOT zinc rusts OR zinc loses electrons and forms ions [1] the electrons move on to the iron [1] the iron cannot be oxidised or it cannot rust or it cannot lose electrons [1] CREDIT correct Chemistry that includes the above ideas (c) (i) zinc atoms change into ions, (the zinc dissolves) [1] copper(II) ions change into atoms, (becomes plated with copper) [1] (ii) ions [1] electrons [1] [Total: 10] 4 (a) diffusion [1] different Mr or ozone molecules heavier than oxygen molecules or different densities or oxygen molecules move faster than ozone molecules [1] NOT oxygen is lighter or ozone heavier OR fractional distillation [1] they have different boiling points [1] (b) (i) from colourless (solution) [1] to brown (solution) [1] (ii) I

– loses electrons (to form iodine molecules) [1] must be in terms of electron transfer NOT oxidation number (iii) they (electrons) are accepted by ozone or it is an electron acceptor [1]



© UCLES 2009

(c) (i) correct structural skeleton [1] COND 4bp around both carbon atoms [1] 2bp and 2nbp around sulfur atom [1] NOTE marks 2 and 3 can only be awarded if mark 1 has been scored (ii) water carbon dioxide sulfur dioxide all three [2] any two [1] Accept correct formulae [Total: 11] 5 (a) (i) strong hard light or low density high melting point or high fixed points Accept high strength to weight ratio for [2] it includes marks 1 and 3 any THREE [3] (ii) silicon [1] four [1] (b) diagram to include: each germanium atom bonded 4 oxygen atoms [1] each oxygen to 2 germanium atoms [1] looks or stated to be tetrahedral [1] “tetrahedral” scores mark even if diagram does not look tetrahedral independent marking of three points (c) (i) structural formula of Ge4H10 all bonds shown [1] (ii) germanium(IV) oxide [1] water [1] [Total: 11]



© UCLES 2009

6 (a) (i) burn sulfur in air or oxygen [1] or heat a metal sulfide in air (ii) bleach for wood pulp/cloth/straw or preserve food or sterilising or making wine or fumigant or refrigerant [1] Accept making paper (iii) vanadium(V) oxide accept vanadium oxide or V2O5 or vanadium pentoxide [1] oxidation state not essential but if given it has to be (V) (iv) rate too slow or rate not economic [1] (v) reaction too violent or forms a mist [1] (b) (i) add water to yellow powder or to anhydrous salt [1] it would go green [1] (ii) change from purple or pink [1] to colourless NOT clear [1] (iii) reacts with oxygen in air [1] (c) number of moles of FeSO4 used = 9.12/152 = 0.06 [1] number of moles of Fe2O3 formed = 0.03* [1] mass of one mole of Fe2O3 = 160 g [1] mass of iron(III) oxide formed = 0.03 × 160 = 4.8 g [1] number of moles of SO3 formed = 0.03 [1] volume of sulfur trioxide formed = 0.03 × 24 = 0.72 dm3 [1] If mass of iron(III) oxide greater than 9.12 g, then only marks 1 and 2 available Apply ecf to number of moles of Fe2O3* when calculating volume of sulfur trioxide. Do not apply ecf to integers [Total: 16]



© UCLES 2009

7 (a) (i) heat [1] catalyst [1] (ii) an equation that gives: alkene + alkane or alkene + alkene + hydrogen [1] a correct and balanced equation for the cracking of decane, C10H22 but not but-1-ene [1] (iii) water or steam [1] (b) (i) C4H9OH + 6O2 → 4CO2 + 5H2O [2] If only error is balancing the oxygen atoms [1] (ii) butanol + methanoic acid → butyl methanoate + water [2] correct products or reactants ONLY [1] (c) (i) correct structural formulae [1] each [2] accept either propanol and –OH in alcohol and acid penalise once for CH3 type diagrams For either C3H8O or C3H6O2 [0] (ii) to conserve petroleum or reduce greenhouse effect [1] (d) have same boiling point [1] [Total: 13]





0620 CHEMISTRY








© UCLES 2009

GENERAL INSTRUCTIONS FOR MARKING

• Error carried forward may be allowed in calculations. This will be discussed in the mark scheme. This is not applied when the candidate has inserted incorrect integers or when the answer is physically impossible.

• COND the award of this/these mark(s) is conditional upon a previous mark being awarded. Example – Is the reaction exothermic or endothermic? Give a reason for your choice. Mark scheme exothermic [1] COND a correct reason given [1]. This mark can only be awarded if the candidate has

recognised that the reaction is exothermic.




• In the mark scheme if a word or phrase is underlined it (or an equivalent) is required for the award of the mark.


• OR designates alternative and independent ways of gaining the marks for the question. or indicates different ways of gaining the same mark.

• Unusual responses which include correct Chemistry which answer the question should always be rewarded – even if they are not mentioned in the marking scheme.



© UCLES 2009

1 (a) (i) argon or krypton or helium [1] Accept xenon and radon even though percentages are very small NOT hydrogen (ii) water and carbon dioxide [2] (b) (i) carbon monoxide or lead compounds or CFCs or methane or particulates or unburnt hydrocarbons or ozone [1] (ii) burn a fossil fuel [1] that contains sulfur [1] (iii) at high temperature or inside engine [1] nitrogen and oxygen (from the air) react [1] (c) liquid air [1] fractional distillation [1] [Total: 10] 2 (a) pH < 7 [1] example [1] pH > 7 [1] example [1] NOT amphoteric oxides Be, Al, Zn, Pb, Sn etc. pH = 7 [1] example H2O, CO, NO [1] the two marks are not linked, mark each independently NOT amphoteric oxides Be, Al, Zn, Pb, Sn etc. (b) (i) shows both basic and acidic properties [1] (ii) acidic reacts with sodium hydroxide only [1] amphoteric reacts with both reagents [1] OR only amphoteric oxide reacts with hydrochloric acid [2] [Total: 9] 3 (a) (i) heat/roast/burn in air [1] need both points for mark (ii) ZnO + C → Zn + CO [2] or 2ZnO + C → 2Zn + CO2 unbalanced ONLY [1]



© UCLES 2009

(b) zinc is more reactive [1] it loses electrons and forms ions in preference to iron [1] zinc corrodes not iron [1] NOT zinc rusts OR zinc loses electrons and forms ions [1] the electrons move on to the iron [1] the iron cannot be oxidised or it cannot rust or it cannot lose electrons [1] CREDIT correct Chemistry that includes the above ideas (c) (i) zinc atoms change into ions, (the zinc dissolves) [1] copper(II) ions change into atoms, (becomes plated with copper) [1] (ii) ions [1] electrons [1] [Total: 10] 4 (a) diffusion [1] different Mr or ozone molecules heavier than oxygen molecules or different densities or oxygen molecules move faster than ozone molecules [1] NOT oxygen is lighter or ozone heavier OR fractional distillation [1] they have different boiling points [1] (b) (i) from colourless (solution) [1] to brown (solution) [1] (ii) I

– loses electrons (it is oxidised) [1] (iii) they are accepted by ozone [1] or ozone is an electron acceptor (c) (i) water carbon dioxide sulfur dioxide all three [2] any two [1] (ii) correct structural skeleton [1] COND 4bp around both carbon atoms [1] 2bp and 2nbp around sulfur atom [1] [Total: 11]



© UCLES 2009

5 (a) (i) strong hard light or low density high melting point or high fixed points Accept high strength to weight ratio for [2] it includes marks 1 and 3 any THREE [3] (ii) diagram 1 four silicons around one carbon [1] diagram 2 four carbons around one silicon [1] either diagram looks or stated to be tetrahedral [1] “tetrahedral” scores mark even if diagram does not look tetrahedral independent marking of three points (b) diagram to include each germanium atom bonded 4 oxygen atoms [1] each oxygen to 2 germanium atoms [1] (c) (i) structural formula of Ge3H8 all bonds shown [1] (ii) germanium oxide [1] water [1] [Total: 11] 6 (a) (i) USA or Texas or Louisiana, Japan volcanoes, natural gas, petroleum [1] (ii) bleach for wood pulp/cloth/straw or preserve food or sterilising or making wine or fumigant or refrigerant [1] Accept making paper (iii) vanadium(V) oxide or vanadium oxide or vanadium pentoxide or V2O5 [1] NB oxidation state not essential but if given has to be (V) (iv) rate too slow or rate not economic [1] (v) reaction too violent or forms a mist [1] (b) (i) add water to yellow powder or anhydrous salt [1] it would go green [1] (ii) change from purple or pink [1] to colourless NOT clear [1] (iii) reacts with oxygen in air [1]



© UCLES 2009

(c) number of moles of FeSO4 used = 12.16/152 = 0.08* [1] number of moles of Fe2O3 formed = 0.04 [1] mass of one mole of Fe2O3 = 160 g [1] mass of iron(III) oxide formed = 0.04 × 160 = 6.4 g [1] number of moles of gases formed = 0.08 [1] volume of sulfur trioxide formed = 0.08 × 24 = 1.92 dm3 [1] If mass of iron(III) oxide greater than 12 g, then only marks 1 and 2 available Apply ecf to number of moles of FeSO4* when calculating volume of sulfur trioxide. Do not apply ecf to integers [Total: 16] 7 (a) (i) heat [1] catalyst [1] (ii) equation that gives: alkene + alkane or alkene + alkene + hydrogen [1] a correct and balanced equation for the cracking of decane, C10H22 but not but-1-ene [1] (iii) water or steam [1] (b) (i) C4H9OH + 6O2 → 4CO2 + 5H2O [2] If only error is balancing the oxygen atoms [1] (ii) butanol + propanoic acid → butyl propanoate + water [2] correct products or reactants ONLY [1] (c) (i) correct structural formulae [1] each [2] penalise once for CH3 type diagrams For C3H8O [0] (ii) to conserve petroleum or reduce greenhouse effect [1] (d) have same boiling point [1] [Total: 13]





0620 CHEMISTRY








© UCLES 2009

1 observations bubbles/fizz/tube feels hot/magnesium dissolves [1] lighted splint (1) pops (1) [2] table of results initial boxes correctly completed (1) final boxes correctly completed (1) comparable to supervisor’s results (1) decreasing order (1) [4] (a) differences correctly completed [1] (b) all five bars correctly drawn (3), –1 for each incorrect labelled (1), if points plotted for graph = 1 [4] (c) (i) hydrogen [1] (ii) exothermic/redox/displacement not neutralisation/oxidation/reduction [1] (d) (i) experiment 1/A or from student’s results ecf [1] (ii) sulfuric acid was the most concentrated/strongest [1] (e) (i) greater/higher ignore rate [1] (ii) half the value or half the value from the table/lower/decrease or less [1] (iii) more/larger volume of acid [1] (f) one error source from e.g. heat losses/use of measuring cylinders/magnesium pieces vary in mass/length [1] 2 (a) solution K colourless solution L colourless solution M colourless (1) for all three correct not white/clear [1] (b) check pHs from supervisor’s results pH of solution K approx 8–12 pH of solution L approx 11–14 pH of solution M approx 0–3 (2) –1 for any incorrect [2]



© UCLES 2009

tests on solution K (c) (i) blue precipitate (1)

deep/royal blue solution or precipitate dissolves (1) [2] (ii) white (1) precipitate (1) [2] (iii) no reaction/change/colourless solution [1] tests on solution L (d) (i) blue precipitate (1) [1] (ii) white precipitate (1) dissolves/clears (1) [2] (iii) brown (1) [1] tests on solution M (e) white (1) precipitate (1) [2] (f) weak (1) alkali/base (1) or ammonia (2) [2] (g) strong (1) alkali/base/hydroxide (1) or sodium hydroxide (2) [2]

(h) chloride (1) not chlorine ion acid (1)

or hydrochloric acid (2) [2]





0620 CHEMISTRY

0620/06 Paper 6 (Alternative to practical), maximum raw mark 60







© UCLES 2009

1 (a) (conical) flask (1) (gas) syringe (1) [2]

(b) to stop loss of gas owtte/stop mixing/so that they don’t react [1]

(c) glowing splint (1) relights (1) lighted splint = 0 ignore ‘pops’ [2]

2 (a) (i) prevent rusting or corrosion/more attractive or shiny/so it doesn’t oxidise not less reactive or answers about value [1]

(ii) silver wears off/will need re-coating ignore references to rusting [1]

(iii) so that silver can coat the spoon/stick to the spoon owtte [1]

(b) negative/cathode [1]

(c) silver [1]

3 (a) add aluminium/Devarda’s alloy and sodium hydroxide (warm) (1)

ammonia/alkaline gas formed/turns red litmus blue (1) for a ‘near miss’ in reagents allow a mark for ammonia [2]

(b) boiling point (1) 100oC (1) [2]

(c) bromine (water) (1) goes colourless (1) not clear [2]

4 (a) Table of results Initial temperature boxes correctly completed (2) 24 26 25 24 26 Highest temperature boxes correctly completed (2) 39 37 35 31 29 [4] Differences correctly completed (1) 15, 11, 10, 7, 3, allow ecf [1]



© UCLES 2009

(b) all 5 bars correctly drawn (2) - 1 for each incorrect

labelled in the centre (1)

correct scale (at least half the grid for ‘y’ axis) (1) [4] If plotting instead of bars only scale mark available

(c) exothermic/displacement/redox not oxidation, reduction or neutralisation [1]

(d) (i) experiment 1/A [1]

(ii) sulfuric acid was most concentrated/strongest [1]

(e) (i) greater/higher ignore reference to rate [1]

(ii) half the value/half the value from the table/lower or less [1] allow 7.5 as a temperature change or 31.5 as a final temperature

(iii) more/larger volume of acid for magnesium to react in [1]

(f) one error source from:

heat losses/use of low accuracy measuring cylinders/magnesium pieces vary in length or mass [1]

5 (b) pH of solution L 11-14 [1]

(d) (i) blue precipitate (1) both for one mark (soluble in excess = 0) [1] (ii) white (1) precipitate (1)

dissolves/clears/soluble in excess (1) [3]

(c) weak (1) alkali/base (1) or ammonia (2) [2]

(d) hydrochloric acid (2) or acid (1) chloride ion (1) not chlorine ion [2]

6 (a) points plotted correctly (2) - 1 for any incorrect smooth curve (1) suitable scale (1) axes labelled (units not essential) (1) [5] accept plot of loss in mass against time

(b) from graph, 180 g (ignore no units) (1) indication on graph (1) [2]

(c) gas given off [1]



© UCLES 2009

(d) to prevent loss of acid not loss of water or steam [1] (e) 4 minutes [1]

(f) sketched curve above original (1) levelling out at 174 s or heading towards it (1) [2] 7 (a) pestle/mortar/solvent/sand (any three) ignore water and/or heat [3] (b) NB marks can be obtained from a diagram

chromatography or chromatogram (1) paper (1) apply spot/extract to paper (1) description or name of solvent used (1) and separation e.g. spots on paper (1) (max 4) [4]

If water used as solvent (max 3) If paper dipped into extract (max 3) If method would not work (max 2)





0620 CHEMISTRY







© UCLES 2010

Question Number

Key Question Number

Key

1 D 21 C

2 B 22 D

3 A 23 A

4 C 24 A

5 D 25 B

6 B 26 A

7 B 27 D

8 D 28 C

9 D 29 C

10 B 30 A

11 D 31 A

12 B 32 A

13 B 33 D

14 B 34 B

15 D 35 B

16 A 36 A

17 B 37 B

18 D 38 B

19 C 39 C

20 B 40 D





0620 CHEMISTRY







© UCLES 2010

Question Number

Key Question Number

Key

1 D 21 A

2 A 22 A

3 B 23 D

4 D 24 C

5 B 25 A

6 D 26 B

7 B 27 C

8 B 28 D

9 D 29 A

10 C 30 C

11 B 31 D

12 D 32 A

13 B 33 A

14 A 34 A

15 C 35 B

16 B 36 B

17 D 37 D

18 B 38 C

19 B 39 B

20 D 40 B





0620 CHEMISTRY







© UCLES 2010

Question Number

Key Question Number

Key

1 D 21 A

2 D 22 A

3 C 23 D

4 A 24 C

5 B 25 B

6 D 26 A

7 B 27 D

8 B 28 A

9 D 29 C

10 B 30 D

11 B 31 C

12 D 32 A

13 B 33 A

14 A 34 A

15 B 35 B

16 D 36 B

17 B 37 C

18 B 38 D

19 D 39 B

20 C 40 B





0620 CHEMISTRY








© UCLES 2010

1 (a) (period) 2 / period II [1] (b) (i) O / O2 / oxygen [1] (ii) F / F2 / fluorine [1] (iii) Li / lithium [1] (iv) C / carbon [1] (v) Be / beryllium [1] (vi) N / N2 / nitrogen [1] (c) atoms; protons [2] [Total: 9] 2 (a) thermal decomposition [1] (b) (i) carbon dioxide [1] (ii) (colourless) to white / milky IGNORE: goes cloudy [1] (c) (i) calcium oxide blown onto surface of iron / mixed with iron / blown into furnace with iron /

mixed in furnace with iron; [1] forms slag / removes impurities (or named impurities) in iron / reacts with silicon dioxide /

reacts with phosphorus oxides / reacts with acidic oxides [1] (ii) mixture of metal with other metals or mixture of metal(s) with non-metals [1] (iii) neutralising acid soils / neutralising acidic lakes / making cement / making limewater /

limewash for buildings ALLOW: paint [1] (iv) 2; H2O [2] (v) calcium chloride [1] [Total: 10]



© UCLES 2010

3 (a) balloons / diving / cryogenics / coolant / arc welding / protective atmosphere / lasers [1] NOT: hot air balloons

(b) (i) nucleus [1]

(ii) 3rd box down ticked (helium has complete outer shell) [1]

(iii) 18 [1]

(iv) Ar34

18 [1]

(c) atoms close together; NOT: atoms on average more than ½ an atom’s diameter from each other atoms randomly arranged [2]

[Total: 7]

4 (a) chloride; [1] NOT: chlorine sulfate [1]

(b) 2.32 IGNORE: wrong units [1]

(c) (i) add sodium hydroxide and aluminium (foil); warm gently; IGNORE: any results given ALLOW: add iron(II) sulfate then concentrated sulfuric acid [2]

(ii) ammonia [1]

(d) (i) flask IGNORE incorrect type; condenser ALLOW: condensing tube; pure water / distilled water; [3]

(ii) any two of:

• distillation

• water (in round bottomed flask) boiled NOT: water heated / water evaporates

• water has a lower boiling point (than ions)

• steam (or water vapour) condenses in condenser / steam or water vapour goes to liquid in condenser

ALLOW: gas goes to liquid in condenser

• solid / ions remain in flask [2]

(iii) medicines / drugs / foodstuffs / (drinking) water [1] [Total: 12]



© UCLES 2010

5 (a) pH 11 [1] (b) 4th box down ticked (slaked lime) [1] (c) (i) plants can’t grow well if soil too acidic / crop yields lower if too acidic [1] ALLOW: plants die if soil acidic ALLOW: plants grow best in neutral soil / plants like neutral soil (ii) any three of: fossil fuels (or correctly named fuel) contain sulfur / sulfur burns / to form sulfur dioxide / sulfur dioxide reacts with oxygen in air / sulfur dioxide (or sulfur trioxide) reacts (or dissolves) with rain [3] (d) (i) neutralisation ALLOW: neutralising [1] (ii) add indicator to flask ALLOW: any named acid-base indicator; [1] any two of:

• add measured amount of calcium hydroxide to flask (or use a volumetric pipette to put the calcium hydroxide in the flask)

• add acid (from burette) into flask

• until indicator changes colour

• record volume of acid added [2] [Total: 10] 6 (a) (i) bauxite / any other ore of aluminium [1] (ii) removal of oxygen (from compound or substance) / gain of electrons / decrease in

oxidation number / addition of hydrogen [1] (iii) too reactive / requires too high a temperature [1] (b) from left to right: lead, nickel, zinc, magnesium [2] (c) (i) (volume) decreases [1] (ii) (volume) increases [1] (d) copper → electrical wiring; aluminium →aircraft bodies ALLOW car bodies or electrical wiring; mild steel → car bodies; stainless steel → chemical plant [4]

[Total: 11]



© UCLES 2010

7 (a) (i) (group of) molecules with similar boiling points / (group of) molecules with similar relative molecular masses / molecules with limited range of boiling points / molecules with limited range of molecular masses / molecules coming off at the same place in the fractionation column

IGNORE: division of petroleum components [1]

(ii) C10H22 ALLOW reasonable mixtures e.g. C7H16 + C3H6 [1]

(b) refinery gas: (fuel) for heating / (fuel) for cars / (fuel) for cooking; gasoline: (fuel) for cars / mowers etc [2]

(c) contains double bonds / contains C=C bonds; compound containing carbon and hydrogen only [2]

(d) (i) 1st box down ticked (catalytic addition of steam) [1]

(ii) correct structure with all atoms and bonds shown OH instead of O-H = 1 mark only [2]

(e) monomers; polymers; [2]

[Total: 11]

8 (a) electrodes [1]

(b) lead / Pb; [1] bromine / Br2 / Br [1] NOT: lead ions, bromide ions

(c) 2nd and 3rd boxes down ticked (1 each) [2]

(d) PbBr2 [1]

(e) (i) solid formed when two solutions mixed [1] NOT: solid formed at bottom of solution

(ii) 3

(iii) 6 [2]

(iv) brain damage in children / affects nervous systems or nerves / poisonous [1] [Total: 10]





0620 CHEMISTRY








© UCLES 2010

1 (a) magnesium oxide / MgO [1] (b) nitrogen dioxide / NO2; ALLOW nitrogen oxide [1] sulfur dioxide / SO2 ALLOW sulfur oxide [1] (c) carbon dioxide / CO2; [1] water / H2O [1] (d) water / H2O [1] (e) carbon dioxide / CO2 [1] [Total: 7] 2 (a) (i) substance containing two (or more) different atoms / elements joined / combined /

bonded BOTH idea of different atoms / elements and bonded needed for 1 mark [1] (ii) (compound) B; [1] it is an ionic giant structure / it is ionic [1] ALLOW it contains ions (iii) C [1] (b) (i) 1st box ticked (conducts when molten) [1] (ii) add (aqueous) silver nitrate; [1] (light) yellow precipitate (BOTH yellow and precipitate required) [1] 2nd mark dependent on correct reagent NOT cream precipitate ALLOW lead nitrate (1) yellow precipitate (1) (c) it is an oxide of a non-metal / iodine is a non-metal [1] [Total: 8]



© UCLES 2010

3 (a) (i) allow between 720 and 820°C (actual = 760 °C) [1] (ii) caesium; [1] rubidium [1] apply listing rules for more than 2 elements (iii) increases (down the group) [1] (b) soft; [1] melting; [1] increases [1]

(c) sodium + water → sodium hydroxide + hydrogen [2] –1 per omission or error

ALLOW = instead of → IGNORE: reference to states NOT: plus instead of + NOT: + energy (d) (i) 2 on left; 2 on right [2] –1 per omission / error (ii) has two atoms (in its molecule) [1] NOT reference to elements / two atoms the same / a compound of two atoms (iii) arrangement: random / not ordered / disordered [1] ALLOW: far apart together; motion: random / (moving) fast / rapid / everywhere / move with ease / freely [1] IGNORE: loosely packed (iv) pair of bonding electrons; [1] 8 electrons in outer shell of each chlorine [1] separate atoms = 0 IGNORE: inner electrons [Total: 16]



© UCLES 2010

4 (a) (i) covalent [1] (ii) C [1] (iii) B [1] (iv) ethanol [1] (v) bromine water ALLOW: bromine / potassium permanganate; [1] turns colourless [1] IGNORE: colour of bromine (b) (i) any two of: same functional group / same general formula / similar chemical properties / gradual change in physical properties [2] ALLOW: (successive members) differ by a CH2 group (ii) correct formula (molecular or displayed) for any alkane apart from ethane [1] correct name corresponding to the formula [1] (c) (i) X placed inside the column at the top [1] (ii) B placed by bottom arrow [1] [Total: 12]



© UCLES 2010

5 (a) (i) decreases / gets smaller [1] NOT disappears / increases in surface area (ii) increases [1] (b) (i) points plotted correctly including 0,0 [2] (–1 per incorrect or no point plotted) curve of best fit drawn [1] (max 1 mark if graph plotted wrong way round) (ii) 44 cm3 [1] ALLOW: 44 / correct reading from incorrect curve in part (i) NOT: incorrect units (iii) all the zinc had been used up / one of the reagents used up [1] ALLOW: the reaction has finished NOT: sulfuric acid used up (iv) lighted splint; [1] (gas) pops / explodes / blows out flame [1] IGNORE: pop test (c) (i) goes faster / more hydrogen given off per minute / more gas given off per unit time / less

time for same amount of gas [1] (ii) goes slower / less hydrogen given off per minute / less gas given off per unit time / more

time for same amount of gas [1] (d) substance which speeds up a reaction [1] ALLOW: changes the rate of reaction [Total: 12]



© UCLES 2010

6 (a) Any three of: high boiling point or high melting point / high density / form coloured compounds or have coloured ions form ions of more than one charge or variable valency / form complex ions / ALLOW: (very) hard / hardness / (good) catalysts [3] (b) (i) different number of neutrons / different nucleon number [1] (ii) 57 [1] (iii) 26 [1] (c) (i) water / damp / humidity; [1] IGNORE: a little or similar when referring to damp / water air / oxygen [1] (ii) suitable method e.g. coating with zinc / coating with unreactive metal / plastic / oil (or grease) / galvanising / sacrificial protection NOT: removing air / water [1] suitable reason e.g. stops air / water reaching surface [1] (reason must be consequential to the method chosen) (d) iron oxide; [1] it loses oxygen / gains electrons / iron decreases oxidation number IGNORE: wrong oxidation numbers NOT addition of hydrogen [1] (e) (i) by (incomplete) combustion of hydrocarbons / carbon compounds [1] ALLOW: (incomplete) combustion of fossil fuels / named carbon containing fuel / carbon

(or hydrocarbons etc) react with air (or oxygen) NOT: reacts with air unqualified (must refer to a carbon compound / fossil fuel) (ii) poisonous / toxic / kills you / suffocates you / stops red blood cells carrying oxygen [1] ALLOW: binds with haemoglobin in place of oxygen NOT: harmful [Total: 14]



© UCLES 2010

7 (a) (i) (boric acid) had dissolved [1] ALLOW acid had diffused / an acid is formed here IGNORE: boric acid is acidic / neutralisation / it is an acid (ii) pH 8 [1] (iii) random movement of particles / mixing up of particles [1] ALLOW: bulk / overall movement of particles from high to low concentration IGNORE: particles move from high to low concentration (iv) idea of neutralisation (of acid by alkali) [1] IGNORE: returned to neutral (b) (i) CON2H4 [1] ALLOW: any order of atoms / (NH2)2CO (ii) 60 [1] (c) (i) nitrogen [1] IGNORE: nitrates (ii) to increase crop / plant growth / speeds up plant growth; [1] to put back nitrogen (or nutrients) into the soil / to provide plants with (more) nutrients ALLOW: to supply plants with nitrogen / essential elements [1] IGNORE: makes the soil more fertile / to supply nitrogen gas / N2 (d) Any two of: evaporate some of the water / heat to crystallisation point / heat a little / partially evaporate; NOT heat or evaporate without qualification allow to crystallise / leave in a warm place / leave on the window sill; IGNORE: cool it dry with filter paper [2] NOT: dry in oven unless it implies that the temperature is below 100 °C / very low [Total: 11]





0620 CHEMISTRY








© UCLES 2010

1 (a) magnesium oxide / MgO [1] (b) nitrogen dioxide / NO2; ALLOW nitrogen oxide [1] sulfur dioxide / SO2 ALLOW sulfur oxide [1] (c) carbon dioxide / CO2; [1] water / H2O [1] (d) water / H2O [1] (e) carbon dioxide / CO2 [1] [Total: 7] 2 (a) (i) substance containing two (or more) different atoms / elements joined / combined /

bonded BOTH idea of different atoms / elements and bonded needed for 1 mark [1] (ii) (compound) B; [1] it is an ionic giant structure / it is ionic [1] ALLOW it contains ions (iii) C [1] (b) (i) 1st box ticked (conducts when molten) [1] (ii) add (aqueous) silver nitrate; [1] (light) yellow precipitate (BOTH yellow and precipitate required) [1] 2nd mark dependent on correct reagent NOT cream precipitate ALLOW lead nitrate (1) yellow precipitate (1) (c) it is an oxide of a non-metal / iodine is a non-metal [1] [Total: 8]



© UCLES 2010

3 (a) (i) allow between 720 and 820°C (actual = 760 °C) [1] (ii) caesium; [1] rubidium [1] apply listing rules for more than 2 elements (iii) increases (down the group) [1] (b) soft; [1] melting; [1] increases [1]

(c) sodium + water → sodium hydroxide + hydrogen [2] –1 per omission or error

ALLOW = instead of → IGNORE: reference to states NOT: plus instead of + NOT: + energy (d) (i) 2 on left; 2 on right [2] –1 per omission / error (ii) has two atoms (in its molecule) [1] NOT reference to elements / two atoms the same / a compound of two atoms (iii) arrangement: random / not ordered / disordered [1] ALLOW: far apart together; motion: random / (moving) fast / rapid / everywhere / move with ease / freely [1] IGNORE: loosely packed (iv) pair of bonding electrons; [1] 8 electrons in outer shell of each chlorine [1] separate atoms = 0 IGNORE: inner electrons [Total: 16]



© UCLES 2010

4 (a) (i) covalent [1] (ii) C [1] (iii) B [1] (iv) ethanol [1] (v) bromine water ALLOW: bromine / potassium permanganate; [1] turns colourless [1] IGNORE: colour of bromine (b) (i) any two of: same functional group / same general formula / similar chemical properties / gradual change in physical properties [2] ALLOW: (successive members) differ by a CH2 group (ii) correct formula (molecular or displayed) for any alkane apart from ethane [1] correct name corresponding to the formula [1] (c) (i) X placed inside the column at the top [1] (ii) B placed by bottom arrow [1] [Total: 12]



© UCLES 2010

5 (a) (i) decreases / gets smaller [1] NOT disappears / increases in surface area (ii) increases [1] (b) (i) points plotted correctly including 0,0 [2] (–1 per incorrect or no point plotted) curve of best fit drawn [1] (max 1 mark if graph plotted wrong way round) (ii) 44 cm3 [1] ALLOW: 44 / correct reading from incorrect curve in part (i) NOT: incorrect units (iii) all the zinc had been used up / one of the reagents used up [1] ALLOW: the reaction has finished NOT: sulfuric acid used up (iv) lighted splint; [1] (gas) pops / explodes / blows out flame [1] IGNORE: pop test (c) (i) goes faster / more hydrogen given off per minute / more gas given off per unit time / less

time for same amount of gas [1] (ii) goes slower / less hydrogen given off per minute / less gas given off per unit time / more

time for same amount of gas [1] (d) substance which speeds up a reaction [1] ALLOW: changes the rate of reaction [Total: 12]



© UCLES 2010

6 (a) Any three of: high boiling point or high melting point / high density / form coloured compounds or have coloured ions form ions of more than one charge or variable valency / form complex ions / ALLOW: (very) hard / hardness / (good) catalysts [3] (b) (i) different number of neutrons / different nucleon number [1] (ii) 57 [1] (iii) 26 [1] (c) (i) water / damp / humidity; [1] IGNORE: a little or similar when referring to damp / water air / oxygen [1] (ii) suitable method e.g. coating with zinc / coating with unreactive metal / plastic / oil (or grease) / galvanising / sacrificial protection NOT: removing air / water [1] suitable reason e.g. stops air / water reaching surface [1] (reason must be consequential to the method chosen) (d) iron oxide; [1] it loses oxygen / gains electrons / iron decreases oxidation number IGNORE: wrong oxidation numbers NOT addition of hydrogen [1] (e) (i) by (incomplete) combustion of hydrocarbons / carbon compounds [1] ALLOW: (incomplete) combustion of fossil fuels / named carbon containing fuel / carbon

(or hydrocarbons etc) react with air (or oxygen) NOT: reacts with air unqualified (must refer to a carbon compound / fossil fuel) (ii) poisonous / toxic / kills you / suffocates you / stops red blood cells carrying oxygen [1] ALLOW: binds with haemoglobin in place of oxygen NOT: harmful [Total: 14]



© UCLES 2010

7 (a) (i) (boric acid) had dissolved [1] ALLOW acid had diffused / an acid is formed here IGNORE: boric acid is acidic / neutralisation / it is an acid (ii) pH 8 [1] (iii) random movement of particles / mixing up of particles [1] ALLOW: bulk / overall movement of particles from high to low concentration IGNORE: particles move from high to low concentration (iv) idea of neutralisation (of acid by alkali) [1] IGNORE: returned to neutral (b) (i) CON2H4 [1] ALLOW: any order of atoms / (NH2)2CO (ii) 60 [1] (c) (i) nitrogen [1] IGNORE: nitrates (ii) to increase crop / plant growth / speeds up plant growth; [1] to put back nitrogen (or nutrients) into the soil / to provide plants with (more) nutrients ALLOW: to supply plants with nitrogen / essential elements [1] IGNORE: makes the soil more fertile / to supply nitrogen gas / N2 (d) Any two of: evaporate some of the water / heat to crystallisation point / heat a little / partially evaporate; NOT heat or evaporate without qualification allow to crystallise / leave in a warm place / leave on the window sill; IGNORE: cool it dry with filter paper [2] NOT: dry in oven unless it implies that the temperature is below 100 °C / very low [Total: 11]





0620 CHEMISTRY








© UCLES 2010

1 (a) (i) same number of protons and electrons [1] (ii) all have the same number of protons / same proton number / same atomic number [1] (iii) more electrons than protons [2] number of protons and electrons not equal ONLY [1] (iv) same number of protons (and electrons) / same proton number / same atomic number [1] different number of neutrons / different mass number / nucleon number [1] (b) (i) 2 + 8 + 5 [1] (ii) 3 / 5 [1] (iii) non-metal because it accepts electrons / needs 3e to complete outer energy level / because it is in Group V or 5e in outer shell [1] note need both non-metal and reason for [1] [Total: 9] 2 (a) (i) harder / stronger / any sensible suggestion which relates to better properties for purpose e.g. stays sharp longer / cuts better / more corrosion resistant [1] (ii) zinc [1] (b) (i) lattice [1] (ii) regular pattern of one type of atom [1] with different atom interspersed [1] can show the difference – size, shading, label etc. (iii) can change its shape by force / plastically deform / can be hammered into sheets / can

bend etc. [1] (iv) particles / ions / atoms / layers [1] cond can slide past each other [1] or metallic bond is non-directional [1] particles can move past each other [1]



© UCLES 2010

(c) (i) tin(IV) oxide + carbon → tin + carbon dioxide [1] not carbon monoxide as a reductant accept carbon monoxide as a product not tin(IV) accept correct symbol equation (ii) water [1] carbon dioxide [1] (iii) correct labels for (pure) copper cathode [1] impure copper anode [1] electrolyte copper(II) sulfate / any soluble copper(II) salt / Cu2+ [1] if labels on electrodes reversed [0] (iv) wires / pipes / jewellery / nails / roofing / ammunition / coins / cookware / catalyst /

sculpture [1] [Total: 15] 3 (i) chemical [1] (ii) from right to left [1] not through salt bridge

(iii) Br2 + 2e → 2Br- [2] for Br- as product [1] (iv) reduction because electron gain [1] / because oxidation number decreases need both points (v) Fe3+ [1] (vi) any correct discussion of the reactivity of the halogens [1] e.g. the more reactive the halogen the higher the voltage not better conductor [Total: 7]



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4 (a) (i) nitrogen 2+5 [1] (ii) needs three electrons [1] to complete energy level [1] (b) (i) expensive metal / iron cheaper / better catalyst [1] (ii) high pressure favours side with smaller volume / fewer moles [1] this is right hand side / product / ammonia side [1] (iii) recycled / sent over catalyst again [1] accept used again (iv) advantage high yield [1] disadvantage slow reaction rate etc [1] [Total: 9] 5 (a) (i) many (simple) molecules form one (large) molecule / monomer molecules form one

polymer molecule [1] (ii) addition - polymer is the only product [1] accept - nX � Xn condensation polymer and simpler molecules formed [1] accept nX � Xn + nHCl / H2O

(b) (i) C12H26 → C8H18 + 2C2H4 [1] / any other correct version (ii) ethane and chlorine give range of products [1] / ethene more readily available than ethane / waste half chlorine as hydrogen chloride / ethene more reactive than ethane (iii) electrolysis [1] aqueous sodium chloride [1] (iv) must have three correct units [1] cond continuation [1] accept –(CH2–CH(Cl))n– [Total: 9]



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6 (a) (i) does not form compounds / does not accept and does not lose electrons / has full outer shell/has 8e in outer shell / it is a Noble Gas / it is in Group 0/8 [1]

(ii) small number of outer electrons / lose electrons then positive [1] large number of outer electrons / gain electrons then negative [1] (iii) any two from nitrogen, oxygen and fluorine [1] accept symbols / molecular formulae (b) (i) zinc / aluminium / lead / tin / chromium [1] (ii) white precipitate [1] precipitate dissolves / colourless solution forms / forms a clear solution / soluble in excess [1] (c) (i) LiF [1] NF3 [1] (ii) LiF has higher mp / bp LiF is a (crystalline) solid, NF3 is probably a gas / a liquid / LiF is less volatile as liquids only LiF conducts LiF is soluble in water, NF3 is not when both solids LiF is harder any two [2] (iii) LiF is an ionic compound [1] NF3 is a covalent/molecular compound [1] for stating that one is ionic and the other covalent [1] without specifying which is which [Total: 13] 7 (i) methane / water vapour / oxides of nitrogen / hydrofluorocarbons / perfluorocarbons /

ozone [1] not sulfur dioxide (ii) living organisms / plants and animals / cells [1] produce energy (from food / glucose / carbohydrates) [1] this forms carbon dioxide (could be in an equation) [1] (iii) when growing the crop removed carbon dioxide from atmosphere [1] / crop photosynthesised and used carbon dioxide combustion returned the carbon dioxide [1] (iv) increased combustion [1] of fossil fuels / named fossil fuel [1] or deforestation [1] less photosynthesis [1] not greater population

[Total: 8]



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8 (a) filter / centrifuge / decant [1] (partially) evaporate / heat / boil [1] allow to crystallise / cool / let crystals form [1] dry crystals / dry between filter paper / leave in a warm place to dry [1] “dry” on its own must be a verb evaporate to dryness only marks 1 and 2 note if discuss residue only mark 1 (b) number of moles of HCl used = 0.04 × 2 = 0.08

number of moles CoCl2 formed = 0.04 number of moles CoCl2.6H2O formed = 0.04

mass of one mole of CoCl2.6H2O = 238 g maximum yield of CoCl2.6H2O = 9.52g [4] accept 9.5 g mark ecf to moles of HCl do not mark ecf to integers to show that cobalt(II) carbonate is in excess number of moles of HCl used = 0.08 must use value above ecf mass of one mole of CoCO3 = 119g number of moles of CoCO3 in 6.0g of cobalt(II) carbonate = 6.0/119 = 0.050 [1] reason why cobalt(II) carbonate is in excess 0.05 > 0.08/2 [1] [Total: 10]





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1 (a) E [1] (b) A C E need all three [1] (c) A [1] (d) F [1] (e) C [1] (f) D F need both but not more [1]

[Total: 6] 2 (a) (i) heat / roast / combustion / high temperature [1] accept burn in air / oxygen [1] any incorrect Chemistry MAX [1] (ii) ZnO + C → Zn + CO [1] OR 2ZnO + C → 2Zn + CO2 the equation must balance, if not [0] not carbon monoxide as a reactant / (iii) fractional [1] distillation [1] (b) (i) making alloys / brass / named alloy which contains zinc [1] galvanising / sacrificial protection / electroplating [1] accept galvanising / one specific use which depends on galvanising zinc coated screws / roofing / buckets / sinks not just plating other metals (ii) positive ions / cations [1] not nuclei / atoms delocalised / free / mobile or sea of electrons [1] bond is attraction between (positive) ions and delocalised electrons [1] it is a good conductor because there are delocalised / free / mobile electrons [1] Note must be clear that electrons are moving / carry charge / reason why it is a good conductor

[Total: 11]



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3 (a) volume given off (in that 20 s interval) [1] divided by 20 [1] accept 48/20 for [2] Answer to 3 (a) may appear twice, both in 3 (a) and 3 (b). Please ignore in 3 (b). (b) 0.6 (cm3/s) [1] (c) concentration [1] of hydrogen peroxide decreases [1]

for hydrogen peroxide used up ONLY [1] not reagent / reactant (d) rate increases / doubles [1] catalyst has bigger surface area / more catalyst particles exposed [1] more collisions [1] not more catalyst / higher concentration of catalyst / more molecules of catalyst

OR

volume of oxygen the same [1] oxygen from hydrogen peroxide (not catalyst) [1] amount / number of moles the same [1]

OR

amount/mass/volume/number of moles of hydrogen peroxide the same [2]

catalyst chemically unchanged ONLY [1] reactants have not changed (only the catalyst) [1] accept catalyst does not react [1]

[Total: 11]

4 (a) (i) chromium is harder has higher density has higher melting point / boiling point / fixed points stronger any TWO [2] accept sodium comments must be comparison chromium is hard [0]

(ii) both chromium and sodium have to be mentioned explicitly or implicitly. sodium is more reactive is acceptable sodium is a reactive metal is not acceptable chromium has more than one oxidation state, sodium has one chromium forms coloured compounds, sodium compounds are white / sodium does not sodium reacts with cold water, chromium does not chromium forms complex ions, sodium does not accept chromium has catalytic properties, sodium does not any TWO [2]



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(b) (i) appearance/shiny/more attractive/decoration resist corrosion / rusting hard surface any TWO [2] NOT becomes harder / stronger (ii) Cr2(SO4)3 [1] ignore correct charges on ions (iii) Cr3+ + 3e → Cr [2] Cr3+ to Cr only [1] ignore comments about sulfate ion (iv) oxygen / O2 [1] (v) to replace chromium ions (used to plate steel) [1] / chromium sulfate used up copper ions replaced from copper anode [1] / solution of copper sulfate does not change not just that anode is not made of chromium

[Total: 12] 5 (a) (i) contains carbon, hydrogen and oxygen [1] accept example ratio 2H : 1O [1] not contains water ignore comments about carbon (ii) living organism / plants and animals / cells [1] obtain energy from food [1] not burn negates energy mark (iii) carbohydrates contain oxygen [1] (iv) as a fertiliser / manure [1] (b) (i) 80 cm3 of oxygen therefore 40 cm3 of methane [1] 40/60 × 100 = 66.7 % [1] accept 66 % and 67 % no ecf (ii) add sodium hydroxide(aq) / alkali [1] carbon dioxide dissolves, leaving methane [1]

[Total: 10]



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6 (a) same general formula consecutive members differ by CH2 same chemical properties same functional group physical properties vary in predictable way / give trend – mp increases with n etc. common methods of preparation any THREE [3] (b) (i) they have the same molecular formula [1] not general formula different structures / structural formulae [1] (ii) CH3-CH2-CH(OH)-CH3 / (CH3)3C-OH [1] not ether-type structures NOTE butan-2-ol and 2-methylpropan-2-ol acceptable (c) (i) air/oxygen / (acidified) potassium chromate(VI) / (acidified) potassium manganate(VII) [1] must have oxidation states (ii) carboxylic acid / alkanoic acid [1] CH3-CH2-CH2-COOH / C3H7COOH / C4H8O2 [1] accept C4H7OOH (d) (i) measure volume of carbon dioxide [1] time [1] accept day / hour for time mark (ii) increase in temperature / more yeast present / yeast multiplies [1] (iii) glucose used up [1] accept sugar not reagent / reactant concentration of ethanol high enough to kill/poison yeast / denature enzymes [1] not kill enzymes (iv) to prevent aerobic respiration [1] / ethanol would be oxidised / ethanoic acid/ acid formed / lactic acid formed / carbon

dioxide and water formed

[Total: 15]



© UCLES 2010

7 (a) (i) kills microbes / bacteria / fungi / micro-organisms etc. [1] (ii) as a bleach [1] (iii) burn / heat sulfur in air / oxygen [1] (b) oxygen [1] vanadium oxide / vanadium(V) oxide / vanadium pentoxide [1] not an incorrect oxidation state 400 °C to 450 °C [1] water [1] (c) (i) proton donor [1] (ii) measure pH / use pH paper [1] sulfuric acid has the lower pH [1] accept colours / appropriate numerical values OR measure electrical conductivity [1] sulfuric acid is the better conductor [1] OR add magnesium / named fairly reactive metal [1] ethanedioic acid gives the slower reaction [1] NOTE result must refer to rate not amount OR add a carbonate [1] ethanedioic acid gives the slower reaction [1] NOTE result must refer to rate not amount (d) (i) how many moles of H2SO4 were added = 0.02 × 0.3 = 0.006 [1] (ii) how many moles of NaOH were used = 0.04 × 0.2 = 0.008 [1] (iii) sulfuric acid [1] only mark ecf if in accord with 1:2 ratio and with values from (i) and (ii). reason 0.006 > 0.008/2 [1] for ecf mark candidate must use 1:2 ratio in answer (iv) less than 7 [1]

[Total: 15]





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© UCLES 2010

1 (a) to complete the outer shell (of oxygen) / full outer or valence shell / 8 (electrons) in outer shell / Noble gas structure / to complete outer shell / to complete the octet

ignore reference to hydrogen atoms / reference to accepting / sharing or gaining electrons [1] (b) loses (one) electron [1] not loses electrons (c) opposite charges attract / electrostatic attraction / positive attracts negative / + and – attract

[1] (d) in solid ions cannot move / flow / no free ions / ions in a lattice [1] in solution ions can move / flow / mobile ions / ions free (to move) [1]

[Total: 5] 2 (a) 23p 23e 28n [1] 23p 20e 28n [1] 23p 23e 27n [1] (b) (i) (contains) iron [1] cond with other element(s) / compounds / suitable named element [1] if iron is absent = 0 (ii) mild steel [1] cars / fridges / white goods / construction etc. [1] credit any sensible suggestion e.g. roofing, nails, screws, radiators or stainless steel [1] cutlery / chemical plant / jewellery / (kitchen) utensils / named kitchen utensil / in cars /

surgical equipment / car exhausts etc. [1] not vanadium steel (this is in the question) (c) (i) V2O3 [1] VO2 [1] (ii) add sodium hydroxide(aq) or other named alkali [1] not ammonia cond vanadium(IV) oxide dissolves / reacts [1] filter (to remove vanadium(III) oxide) [1]

[Total: 12]



© UCLES 2010

3 (a) (i) silver, tin (cobalt and magnesium not possible to decide) [2] for silver less reactive then tin = 1 (ii) magnesium and cobalt salt / compound / ions or cobalt and magnesium salt / compound / ions [1] (iii) Sn + 2Ag+ � Sn2+ + 2Ag [2] all species correct = 1 balancing = 1 Sn to Sn2+ oxidation (can be written separately or as a correct half-equation) [1] (b) no reaction [1] Mg(OH)2 � MgO + H2O accept multiples [1] (c) (i) it forms positive ions / loses or gives electrons [1] electrons move / flow from this electrode / enter the circuit / electrons flow from negative to positive (so it is negative) [1] (ii) bigger voltage of Zn/Cu cell than Sn/Cu cell or zinc is negative relative to tin (in the third cell) [1] (iii) magnesium / more reactive metal (must be named) instead of zinc not anything above calcium in the reactivity series or silver / less reactive metal (must be named) instead of copper or use (more) concentrated acid [1] (iv) polarities correct that is Zn - and Sn + [1] 0.6 V [1]

[Total: 14] 4 (a) (i) H2 on RHS [1] ignore any other species on RHS rest of equation fully correct i.e. 2H+ + 2e � H2 [1] (ii) H+ removed / escapes / discharged / used up / reduced [1] (equilibrium) moves to RHS / more water molecules ionise or dissociate / forward reaction favoured [1] (iii) oxygen / O2 [1] not O (iv) carbon / graphite / platinum (electrode) [1] (b) (i) to make ammonia / in petroleum processing / balloons / rocket fuel / fuel for cars /

hardening of fats / fuel cells / fuel (unqualified) / making hydrochloric acid [1] (ii) to sterilise / disinfect it / kill bacteria / bugs / microbes / micro-organisms / germs [1]



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(c) (i) (reference to) volume and time / how long it takes [1] (ii) carry out experiment with different intensities of light / one in light and one in dark / repeat experiment in reduced light [1] measure new rate which would be faster or slower depending on light intensity [1]

[Total: 11] 5 (a) (i) Mg + 2CH3COOH � (CH3COO)2Mg + H2 [1] correct formula of magnesium ethanoate [1] ignore charges sodium ethanoate + water [1] (ii) ethyl ethanoate [1] displayed formula [1] (b) (i) add up to 5.8 g [1] (ii) moles of C atoms = 2.4/12 = 0.2 moles of H atoms = 0.2/1 = 0.2 moles of O atoms = 3.2/16 = 0.2 all three correct = 2 [2] two correct = 1 empirical formula CHO [1] (iii) 116/29 = 4 [1] C4H4O4 [1] correct formula with no working scores both marks. (iv) HOOCCH=CHCOOH / CH2=C(COOH)2 [2]

[Total: 13] 6 (a) (i) 6e between two nitrogen atoms (can be any combination of dots or crosses) [1] 1 lone pair on each nitrogen atom [1] (ii) SOLID GAS PATTERN regular / lattice (not fixed) random / irregular / no pattern [1] DISTANCE close far apart / spread out [1] MOVEMENT vibrate / fixed / no motion moving / translational [1] (b) (i) particles/molecules have more energy / move faster [1] collide harder / collide more frequently / more collisions / collide with more force (with the

walls) [1]



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(ii) (1) nitrogen has smaller Mr / lighter molecules / lower density [1] nitrogen molecules / particles move faster (than chlorine molecules) [1] (2) at higher temperature nitrogen molecules or particles (not atoms) move faster /

have more energy [1]

[Total: 10] 7 (a) (i) lighter / light / lightweight / lower density [1] does not corrode / rust / oxidised [1] ignore cheaper / easier to mould (ii) credit any two sensible suggestions e.g. rope / clothing / netting / string / carpets / fishing

line / fishing nets / parachutes / tyres / tents / bottles / thread / umbrellas / curtains / toothbrushes / cassettes / video tapes [2]

(iii) non-biodegradeable / do not rot / do not decompose / persist for years / accumulate landfill sites limited / getting filled up visual pollution danger to fish / animals (burn to form) toxic gases / harmful gases / pollutant gases / acidic gases / CO / HCl /

HF / HCN not oxides of nitrogen / sulfur any three [3] (b) (i) propene / propylene [1] accept prop-1-ene not prop-2-ene CH3-CH=CH2 [1] double bond must be shown (ii) correct repeat unit (one or more whole repeat units must be given) [1] cond continuation [1] (c) (i) amide / peptide / polypeptide [1] (ii) protein / polypeptide [1] (iii) H2N(CH2)6NH2 [1] HOOC(CH2)8COOH

[Total: 15]





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© UCLES 2010

1 (a) Table of results for Experiment 1 initial temperature boxes completed correctly (1) other temperature boxes correctly completed (1) comparable to supervisors (1) i.e. decreasing [3] (b) Table of results for Experiment 2 initial/final temperature boxes completed correctly (1) comparable to supervisors (1) i.e. increasing [2] (c) all points correctly plotted (3), –1 for any incorrect best fit straight line graphs drawn with a ruler (2) labels (1) [6] (d) (i) value from graph (1) shown clearly (1) [2] (ii) value from graph (1) shown clearly (1) [2] (e) endothermic [1] (f) temperature (changes) would be smaller owtte (1) more water (1) ignore references to rate [2] (g) solid would dissolve/react slower or take longer to observe final temperature (1) smaller surface area (1) [2] (h) lag apparatus/use a lid or insulate /use digital thermometer/ use a pipette or burette instead of measuring cylinder/use data logging device owtte not repeat and average [1] [Total: 21] 2 (a) yellow (1) precipitate (1) [2] (b) white (precipitate) [1] (c) effervescence/fizz/bubbles (1) pH paper blue/purple/> 7 (1) smell (1) max 2 ignore references to hydrogen [2]



© UCLES 2010

(d) yellow/brown/orange colour hot (1) faded/goes white when cool (1) [2] (e) bubbles/fizz etc (1) limewater turns milky (1) [2] (f) (i) white precipitate (1) dissolves/clears (1) [2] (ii) white precipitate (1) dissolves/clears (1) see Supervisor’s report [2] (g) ammonia ignore hydrogen [1] (h) silver/lead (1) nitrate (1) [2] (i) zinc (1) allow aluminium dependent on (f) (ii) gives off carbon dioxide (when acid added) (1) carbonate (1) [3] [Total: 19]





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© UCLES 2010

1 (a) Table of results for Experiment 1 initial temperature boxes completed correctly (1) other temperature boxes correctly completed (1) comparable to supervisors (1) i.e. decreasing [3] (b) Table of results for Experiment 2 initial/final temperature boxes completed correctly (1) comparable to supervisors (1) i.e. increasing [2] (c) all points correctly plotted (3), –1 for any incorrect best fit straight line graphs drawn with a ruler (2) labels (1) [6] (d) (i) value from graph (1) shown clearly (1) [2] (ii) value from graph (1) shown clearly (1) [2] (e) endothermic [1] (f) temperature (changes) would be smaller owtte (1) more water (1) ignore references to rate [2] (g) solid would dissolve/react slower or take longer to observe final temperature (1) smaller surface area (1) [2] (h) lag apparatus/use a lid or insulate /use digital thermometer/ use a pipette or burette instead of measuring cylinder/use data logging device owtte not repeat and average [1] [Total: 21] 2 (a) yellow (1) precipitate (1) [2] (b) white (precipitate) [1] (c) effervescence/fizz/bubbles (1) pH paper blue/purple/> 7 (1) smell (1) max 2 ignore references to hydrogen [2]



© UCLES 2010

(d) yellow/brown/orange colour hot (1) faded/goes white when cool (1) [2] (e) bubbles/fizz etc (1) limewater turns milky (1) [2] (f) (i) white precipitate (1) dissolves/clears (1) [2] (ii) white precipitate (1) dissolves/clears (1) see Supervisor’s report [2] (g) ammonia ignore hydrogen [1] (h) silver/lead (1) nitrate (1) [2] (i) zinc (1) allow aluminium dependent on (f) (ii) gives off carbon dioxide (when acid added) (1) carbonate (1) [3] [Total: 19]





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© UCLES 2010

1 (a) Table of results for Experiment 1

volume of acid box completed correctly (1) comparable to supervisors (1) (b) Table of results for Experiment 2 volume of acid box completed correctly (1) comparable to supervisors (1) –1 if not 1 decimal place [4] (c) pink (1) to colourless (1) not clear [2] (d) (i) hydroxide [1] (ii) neutralisation [1] (e) (i) experiment 2 [1]

(ii) experiment 2 2× volume experiment 1 [1] (iii) alkaline solution G more concentrated/stronger (1) or converse

2× as concentrated (2) [2] (f) half value from table result for experiment 2 (1) cm3 (1) half volume of G used (1) max 2 [2] (g) (i) two sources of error e.g. using a measuring cylinder to measure alkalis/going past end point owtte [2] (ii) two meaningful improvements related to above e.g. use a pipette/burette/repeat experiment or use different indicator [2] [Total: 18] 2 (a) white/colourless crystals [1] (b) melts/turns into a liquid owtte (1) crackles (1) pH paper turns blue/ pH > 7 (1) smell (1) max 2 [2] (c) (i) white (1) precipitate (1) [2] (ii) no change/no reaction owtte [1] (iii) pungent/smelly (gas) (1) indicator paper turns blue or pH > 7 (1) [2]



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(d) solid turns white/colour fades (1) condensation at top of tube (1) acidic gas (1) max 2 [2] (e) (i) green (1) precipitate (1) [2] (ii) white precipitate [1] (iii) (manganate) turns colourless/yellow/orange/brown [1] (f) steam (1) heat given off (1) solid turns green/brown/yellow/orange (1) max 2 [2] (g) ammonia [1] (h) ammonium (1) sulfate (1) [2]

(i) iron (1) (II) (1) sulfate (1) [3] [Total: 22]





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© UCLES 2010

1 (a) ethanol and aluminium oxide boxes correctly labelled [1] (b) arrow towards wool (1) arrow towards solid (1) [2] (c) to prevent suck back or description of suck back owtte (1) effect of suck back e.g. crack tube (1) [2] [Total: 5] 2 (a) to speed up the reaction [1] (b) solid visible owtte e.g. no more solid will dissolve [1] (c) filtration / centrifuge not decant [1] (d) to make sure water (of crystallisation) is not lost / stop dehydration / so crystals do not turn into powder / does not decompose not crystals break [1] (e) no heat needed / not necessary to warm acid (1) carbonates react with acid at room temperature (1) no bubbles would indicate that carbonate is in excess (1) [max 2] [Total: 6] 3 (a) idea of fair test / only one variable [1] (b) nitric acid [1] (c) (i) points plotted (3), –1 for each incorrect smooth curve (1) [4] (ii) value from graph 18 s (1) indication on graph (1) [2] (d) times would be less / reaction quicker (1) particles have more energy / increased collisions (1) [2] [Total: 10]



© UCLES 2010

4 total volume of water boxes correctly completed (1) 10, 11, 12, 13, 14 temperature boxes completed (4) –1 each incorrect 68, 63, 59, 55, 51 [5] (a) appropriate scale for y-axis (1) points plotted correctly (4), –1 for each incorrect best fit straight line graph (1) [6] (b) clear liquid formed / no solid visible owtte [1] (c) value from graph for 9 cm3 of water, around 72 oC (1) extrapolation of straight line shown (1) [2] (d) temperatures at which crystals appear lower (1) solution more dilute in same volume of water / less saturated owtte (1) [2] (e) sketch graph below line (1) label (1) [2]

(f) one improvement from e.g.

don’t use a beaker of cold water to cool solution / do not remove thermometer from the solution / use second person or IT method to note formation of crystals /

repeat linked explanation different rate of heat losses / loss of solid on thermometer / observing formation of first crystals may vary / average mean more accurate / increases reliability [2] not just accurate [Total: 20]

5 (a) (i) blue (1) [1] (ii) blue (1) precipitate (1) [2] (iii) blue precipitate (1) deep / royal blue (1) solution (1) or precipitate dissolves [3] (c) sulfuric acid (2) acid or sulfate only (1) [2] [Total: 8]



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6 (a) bubbles / fizzing / effervescence [1] (b) alkali formed [1] (c) (i) chlorine [1] (ii) indicator bleached / decolourised allow yellow [1] [Total: 4] 7 (a) universal indicator / pH paper (1) not litmus pH of 4–6 / yellow / orange (1) not red [2] (b) sodium hydroxide / carbonate / oxide [1] (c) marks can be obtained from diagram chromatography (1) description of applying E110 to paper (1) use of solvent (1) results / number of spots (1) [4] [Total: 7]





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© UCLES 2010

1 (a) flask (1) pipette (1) burette (1) [3] (b) named indicator (1) colour change (1) [2] not incorrect colour change [Total: 5] 2 correct test (1) result (1) examples given are not the only possible correct responses note incorrect test means zero for result e.g. test for KCl, add sulfuric acid gives white ppt scores

no marks. Except for NaOH, unnamed indicator turns blue or purple scores one mark for the result.

aqueous potassium chloride (nitric acid) silver nitrate / lead nitrate (1) white precipitate (1) ethanol lighted splint (1) flame produced (1) allow dichromate / manganate and correct colour change not b.p. sodium hydroxide solution named indicator (1) correct colour change or pH (1) allow named metal salt solution and correct ppt. colour [Total: 6] 3 (a) all points plotted correctly (2), –1 each incorrect straight line (1) [3] (b) gas / carbon dioxide given off [1] not hydrogen gas given off (c) prevent loss of acid / liquid [1] (d) (i) Experiment 1 [1] (ii) (in Experiment 2) the temperature of the acid was lower / converse [1] (e) 18.5 minutes ±1/2 small square (1) extrapolation on grid (1) [2] (f) sketched line to the left of Experiment 1 line [1] [Total: 10]



© UCLES 2010

4 (a) initial temperature boxes correctly completed 23 (1) final temperature boxes completed (2) –1 each incorrect 21 20 19 17 [3] (b) initial temperature boxes correctly completed 22 (1) final temperature boxes correctly completed (1), –1 each incorrect 26 28 30 [2] (c) points plotted correctly (3), –1 for each incorrect best fit straight line graphs (2) labels (1) [6] (d) (i) value from graph 34 oC (1) shown clearly on graph (1) [2] (ii) value from graph 18 oC (1) shown clearly (1) [2] (e) endothermic [1] (f) temperature changes would be smaller / half owtte (1) more water (1) [2] (g) solid would dissolve slower / react slower or take longer to reach final temperature (1) smaller surface area (1) [2] allow converse e.g. dissolves faster or reaches final temperature faster larger surface area [Total: 20] 5 (a) yellow (1) precipitate (1) [2] (b) effervescence / fizz / bubbles (1) pungent smell (1) pH paper blue / purple / >7 (1) [3] ignore white ppt. (d) carbon dioxide [1] (e) zinc (1) carbonate (1) [2] [Total: 8]



© UCLES 2010

6 (a) electroplating [1] (b) (i) chromium (1) (ii) any named chromium salt (1) [2] (c) to stop corrosion owtte (1) to look attractive owtte (1) [2] [Total: 5] 7 specified number / mass of nails (1) add x cm3 sample of water (1) in a test-tube / beaker (1) leave until nails rust and note time (1) not unrealistic time, must be at least one day repeat with other water samples (1) same volume water / number of nails (1) compare / describe results (1) [max 6] [Total: 6]





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© UCLES 2010

1 (a) (i) fractional distillation [1] (ii) A = flask (1) B = condenser (1) [2] (b) alkanes are inflammable / risk of fire owtte [1] (c) octane [1] (d) temperature on the thermometer would rise / be 174oC / pause in the distillation of liquid [1] [Total: 6] 2 (a) (i) measuring cylinder [1] (ii) reaction will happen / is fast with cold acid [1] (b) solid / powder visible / no more solid dissolves / fizzing stops when powder added [1] not precipitate forms, not stops reacting (c) diagram of funnel (1) and filter paper within (1) [2] (d) heat to crystallising point owtte (1) to prevent loss of water of crystallisation (1) [2] not heat and leave to cool [Total: 7] 3 highest temperatures correct (1) 28, 30, 32, 32 temperature rises correct (1) 7, 9, 11, 11 [2] (b) points plotted correctly (2), –1 any incorrect two straight lines through points, must use ruler (1) [3] (c) (i) 0.25 g (1) extrapolation shown (1) [2] accept extrapolation to zero and subsequent mass (ii) all copper sulfate solution used up after 1.5

g zinc added / zinc is in excess / owtte [1] (d) sketch graph to left of original / steeper slope than original (1) rising above original (1) [2] [Total: 10]



© UCLES 2010

4 (a) final volumes completed correctly (2) 13.0 and 34.0 initial volumes completed correctly (1) 0.0 and 8.0 differences correct (1) 13.0 and 26.0 –1 if any readings not to 1 dp, –1 if initial and final readings are reversed [4] (b) hydroxide [1] (c) (i) Experiment 2 / G [1]

(ii) Experiment 2 2× volume experiment 1 [1] (iii) alkaline solution G more concentrated / stronger (1) or converse

2× as concentrated (2) [2] (d) 13 (1) cm3 (1) half volume of G used (1) [3] (e) (i) two sources of error e.g. using a measuring cylinder to measure alkalis / going past end point owtte / conical flask or measuring cylinder not cleaned [2] (ii) two meaningful improvements related to above e.g. use a pipette / burette / repeat experiment or use different indicator / clean conical flask or measuring cylinder [2] [Total: 16] 5 (c) green (solid) [1] (d) (i) green (1) precipitate (1) [2] (ii) white (1) precipitate (1) [2] (e) ammonia [1] (f) ammonium (1) sulfate (1) not a halide (1) [3] [Total: 9]



© UCLES 2010

6 (a) powder has larger surface area (1) speeds up reaction / more collisions (1) [2] (b) red / brown / pink [1] (c) the ice / condensation [1] (d) test add anhydrous copper sulfate / cobalt chloride paper (1) result turns blue / pink (1) [2] [Total: 6] 7 (a) (i) less than 7 [1] (ii) colour of orange drink obscures indicator colour owtte [1] (b) chromatography (1) apply orange drink to paper (1) use of solvent (1) comparison of spot heights or Rf with E numbers and/or carotenes (1) [4] [Total: 6]





0620 CHEMISTRY



• Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the October/November 2011 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.





Question Number

Key Question Number

Key

1 D 21 D

2 D 22 D

3 D 23 A

4 D 24 D

5 C 25 A

6 C 26 C

7 C 27 A

8 B 28 C

9 A 29 D

10 B 30 C

11 B 31 B

12 D 32 C

13 C 33 B

14 B 34 D

15 B 35 B

16 B 36 C

17 B 37 D

18 A 38 A

19 B 39 D

20 C 40 A





0620 CHEMISTRY








Question Number

Key Question Number

Key

1 D 21 D

2 D 22 C

3 D 23 A

4 C 24 C

5 D 25 C

6 B 26 A

7 C 27 C

8 C 28 D

9 B 29 A

10 A 30 D

11 B 31 B

12 B 32 B

13 D 33 C

14 C 34 B

15 B 35 D

16 B 36 C

17 B 37 A

18 A 38 D

19 D 39 A

20 B 40 D





0620 CHEMISTRY








Question Number

Key Question Number

Key

1 D 21 B

2 C 22 A

3 D 23 D

4 D 24 C

5 D 25 C

6 B 26 D

7 B 27 A

8 C 28 A

9 A 29 C

10 C 30 D

11 B 31 B

12 B 32 C

13 D 33 B

14 C 34 B

15 B 35 D

16 B 36 C

17 B 37 D

18 A 38 A

19 C 39 D

20 D 40 A





0620 CHEMISTRY









1 (a) (i) medicines / food / (drinking) water / air quality [1] ignore: kitchens / clothes (ii) 1st box down ticked (boils slightly above 100

oC) [1] (b) all 4 correct = 2 marks [2] 2 or 3 correct = 1 mark 0 or 1 correct = 0 marks top right → solvent front bottom right → chromatography paperbottom left → solvent top left → origin line (c) (i) C [1] (ii) A, C and D (all three correct for 1 mark) [1] (iii) B [1] [Total: 7] 2 (a) air / oxygen [1] water [1] allow: damp / humid (b) idea of reaction of the oxygen (in first two weeks) [1] ignore: air reacting (oxygen reacting) with the iron / rusting / iron reacts [1] ignore: reaction with rust / reaction with iron oxide

(after 2 weeks) all the oxygen had reacted / there was no further reaction / reaction had stopped / no more oxygen [1]

ignore: no more air / experiment was finished (c) (at start →) shiny / silvery [1] allow: grey (after 2 weeks →) brown / reddish brown / orange [1] allow: red ignore: dull (d) add (aqueous) sodium hydroxide / (aqueous) ammonia [1] reddish-brown / brown precipitate (both colour and ppt needed) [1] reject: red precipitate note: 2nd mark dependent on correct reagent (e) iron + hydrochloric acid → iron chloride + hydrogen [2] 1 mark for iron chloride; 1 mark for hydrogen ignore: wrong oxidation numbers / numbers in equation [Total: 11]




3 (a) (i) Na / Mg / sodium / magnesium [1] (ii) any two of Si / P / S / Cl (1 mark each) [2] (b) decreases / less metallic / from metals (on left) to non-metals (on right) [1] allow: metals on left and non metals on right ignore: just reference to metals or non-metals alone i.e. metals on left ignore: reactivity decreases (c) atomic number / number of protons [1] ignore: number of electrons (d) (i) Any 4 of: [4]

nucleus in centre of atom neutrons and protons in nucleus number of protons = 13 number of neutrons = 14 number of electrons = 13 electrons on outside of atom electrons in shells / 3 shells 3 electrons in outer shell electron configuration = 2,8,3 allow: marks from labelled diagram

(ii) very good (electrical) conductivity / it is the best conductor / it is a better conductor [1] ignore: good conductor has a low density [1] ignore: other properties (e) Br2 on right [1] correct balance 2 (KBr) and 2(KCl) [1] allow: balance mark if 2Br on right reject: if incorrect species (f) 3rd box down ticked (argon has a complete outer…) [1] [Total: 14]




4 (a) ethene decolourises (bromine water) / bromine goes colourless in ethane [1] ethane does not / no change / remains reddish-brown [1] allow: only ethene decolourises bromine = 2 ignore: ethene reacts and ethane does not

(b) (i) heat / high temperature [1]

ignore: warm allow: quoted values between 300–1000

oC catalyst / named catalyst e.g. aluminium oxide / porous pot [1] ignore: high pressure

(ii) alkene collects above the water / alkene not mixed with water [1] ignore: bubbles / it goes up (iii) 42 [1] (iv) C4H8 / 2C2H4 [1] (c) addition [1] polymerisation [1] [Total: 9]




5 (a) (i) correct points (each within one small square) [2] –1 mark for each incorrect point smooth curve [1] ignore: continuation of curve at either end (ii) 75

oC / the highest [1] allow: values above 75

oC

(iii) the higher the temperature the faster the reaction / speed greater at higher temperature [1]

allow: the higher the temperature the faster the word disappear ignore: gets faster without qualification / faster with temperature / higher temperature

increases rate of collisions / it takes less time the higher the temperature (b) increases / gets faster [1] not: goes fast (c) (i) sodium chloride [1] apply: listing if extra species (ii) VI / vi / 6 / six [1] (iii) forest death / acidifies lakes or rivers / kills fish / plant in lakes or rivers / slows crop growth / leaches harmful minerals from soil / erodes (or corrodes) buildings

(or metals) / kills corals [1] ignore: acid rain / kills animals / kills plants or fish in sea (iv) 2nd box down ticked (calcium oxide) [1] (v) magnesium gains oxygen / increases its oxidation number / gets oxidised [1] allow: loses electrons / Mg gets oxidised

sulfur dioxide loses oxygen / decreases its oxidation number; [1] allow: gains electrons / SO2 gets reduced ignore: repeating what is in the equation note: oxidation and reduction occurs together = 1

[Total: 12]




6 (a) O2 [1] 2 (O2) dependent on O2 [1] (b) carbon monoxide / CO [1] (c) there was no air / the gas was at a low temperature / gas was unburnt [1] ignore: there was no gas / there is no combustion (d) (i) water [1] (ii) heat it / warm it / put in dessicator [1] (iii) gets heavier / increases absorbs carbon dioxide / carbon dioxide has mass / carbon

dioxide added [1] both points needed for 1 (e) (i) cow flatulence / marshes / waste sites / paddy fields [1] allow: bacterial decomposition (ii) global warming / named effect of global warming e.g. rise in air temperature / melting of

polar ice / desertification / more extreme weather [1] ignore: melting of ice unqualified allow: greenhouse effect [Total: 9]




7 (a) 3rd box down ticked (endothermic) [1] (b) (i) ring around OH [1] reject: round OH and C / around OH of COOH (ii) C6H8O7 [1] (c) (i) catalyst / substance which speeds up rate of reaction [1] protein / (substance) found in living things / biological [1] ignore: found in washing powder (ii) filtration [1] allow: decanting (iii) limewater [1] turns milky / cloudy / white precipitate [1] (d) put indicator in flask [1] allow: any named indicator (even if can’t be used for weak acid) add sodium hydroxide (from burette) [1] stop adding / endpoint when indicator changes colour [1] [Total: 11]




8 (a) (i) electrolyte → D [1] allow: (molten) sodium chloride cathode → C [1] (ii) graphite [1] (b) floats on top of the sodium chloride [1] allow: sodium is on top (c) chlorine / Cl2 [1]

allow: Cl reject: chloride (d) (anode →) chlorine / Cl2 [1] allow: oxygen / O2 allow: Cl / O reject: chloride / oxide (cathode →) hydrogen / H2 [1] allow: H [Total: 7]





0620 CHEMISTRY









1 (a) (i) C [1] (ii) A [1] (iii) E [1] (iv) D [1] (v) C [1] (b) (i) limestone / chalk / marble [1] ignore: lime / formulae (ii) 3rd box down ticked (heavier than air) [1] (iii) H2O on right [1] 2(HCl) [1] second mark dependent on correct formula for water [Total: 9]




2 (a) copper → any common use e.g. electrical wiring / pipes jewellery [1] ignore: for alloys / for brass / for wires (unqualified) platinum → any common use e.g. inert electrode / jewellery [1] allow: for catalyst (as long as not incorrect catalyst)

aluminium → any common use e.g. food containers / car (bodies) / aircraft (bodies) / kitchen utensils / pots and pans [1] allow: for roofing / for high voltage electrical cables ignore: for wires / for knives

(b) (i) poisonous / harms nervous system or brain [1] ignore: harmful (without qualification) (ii) protons → 82 [1] neutrons → 125 [1] (c) (i) Any three of: [3]

sodium goes into a ball / gets smaller / disappears

allow: dissolves ignore: reacts moves (over surface) bubbles / effervescence /

ignore: hydrogen given off floats on the water (as it reacts) / fizzes / hissing / crackling

ignore: sound litmus turns blue /

ignore: changes colour (ii) sodium hydroxide [1] hydrogen [1] (iii) electron [1] Ion [1] gains [1] negative [1] [Total: 15]




3 (a) Any two of: [2] temperature mass / amount of manganese(IV) oxide / volume of manganese(IV) oxide size of manganese dioxide particles allow: pressure ignore: concentration (b) (i) the greater the concentration the greater the speed / rate increases with concentration [1]

ignore: concentration increases speed / more oxygen the grater the concentration (ii) less hydrogen peroxide present (in B) / more hydrogen peroxide (in A) [1] allow: hydrogen peroxide less concentrated (in B) (iii) time taken → 27 (s) [1] allow: 26 (s) volume → 37 (cm3) [1] (c) magnesium → copper → manganese → lead [1] ignore: oxide / oxidation numbers [Total: 7] 4 (a) methane [1] (b) arrangement → random / irregularly arranged / no fixed position [1] proximity → close together / touching [1] motion → random/ sliding over each other / movement not entirely free [1] allow: move slightly (c) (i) arrow at tube at bottom left [1] ignore: direction of arrow (ii)

group of (different) molecules / group of (different) hydrocarbons [1] implication of different molecules

with similar / (particular) range of boiling points / molecules with similar molecular masses or small range of molecular masses [1]

(iii) X → naphtha [1] Y → diesel (oil) [1] (iv) structure of ethane showing all atoms and all bonds [1] (v) 2nd box down ticked (saturated hydrocarbon) [1] [Total: 11]




5 (a) molecule → two or more atoms [1] atom → the smallest part [1] ion → an atom that has become [1] (b) (i) pH 13 [1] (ii) 40 [1] (iii) neutralisation [1] (iv) pH decreases / pH goes from higher to lower pH / suitable reference to pH values e.g.

from pH 12 to pH 8 [1] final pH below 7 / stated value below 7 [1] ignore: gets more acidic (c) Any six of: [6]

bubbles (from the electrodes) solution goes yellow(ish) / solution goes green(ish) hydrogen at cathode chlorine at anode

(hydrogen and chlorine gases produced at wrong electrodes = 1) electrodes are graphite / electrodes are carbon electrodes conducts electricity / electrons move in electrodes hydrogen (ions) go to cathode chloride (ions) go to the anode smell of chlorine electrolyte conducts electricity

ignore: hydroxide ions [Total: 14]




6 (a) as a reducing agent / in the blast furnace / for extracting iron or zinc or other suitable metal / to extract metals / in making lime [1]

(b) (i)

layers can slide over each other [1] both ideas of layers and sliding needed

strong bonding in all directions / covalent bonding in all directions / strong bonding in macromolecules in giant structure [1]

both ideas of type of bonding and giant structure needed (ii) for cutting / drill bits / for drills [1] (c) (i) ammonium sulfate [1] ignore: water / hydrogen (ii) nitrogen [1] (d) one pair of electrons in each overlap area [1] (e) 1st box ticked [1] last box ticked [1] [Total: 9]




7 (a) (i) Any two of: [2] have same general formula / have same pattern of formula / members differ by CH2 group have same functional group have similar chemical properties / prepared by similar methods

allow: same chemical properties not: similar properties

show gradual change in physical properties / show trend in boiling points (ii) H H │ │ H – C – C – O – H │ │ H H allow: OH in place of O – H [1] (b) (i) exothermic and temperature increases / goes from 18 to 37 [1] both: exothermic and temperature increase needed for the mark allow: exothermic because heat is given off (ii) grey / black / grey-black [1] not: brown / purple (c) filter (off zinc); [1] note: second mark dependent on filtration for first mark (let alcohol) evaporate / evaporate (off the alcohol) [1] allow: warm gently (to remove some alcohol) allow: use drying agent ignore: heat unqualified / crystallise reject: residue left to dry (d) (i) ZnI2 [1] allow: 5ZnI2 (ii) 2nd answer ringed (giant ionic) [1] allow: underlined or ticked (e) 1 mark for each product [3] zinc nitrate ammonium nitrate not: ammonia nitrate water (f) add (aqueous) sodium hydroxide (and warm) [1] test gas evolved with red litmus paper/ universal indicator paper [1] litmus paper/ universal indicator paper turns blue [1] note: the 2nd and 3rd marks are dependent on the first mark being correct [Total: 15]





0620 CHEMISTRY









1 (a) (i) C [1] (ii) A [1] (iii) E [1] (iv) D [1] (v) C [1] (b) (i) limestone / chalk / marble [1] ignore: lime / formulae (ii) 3rd box down ticked (heavier than air) [1] (iii) H2O on right [1] 2(HCl) [1] second mark dependent on correct formula for water [Total: 9]




2 (a) copper → any common use e.g. electrical wiring / pipes jewellery [1] ignore: for alloys / for brass / for wires (unqualified) platinum → any common use e.g. inert electrode / jewellery [1] allow: for catalyst (as long as not incorrect catalyst)

aluminium → any common use e.g. food containers / car (bodies) / aircraft (bodies) / kitchen utensils / pots and pans [1] allow: for roofing / for high voltage electrical cables ignore: for wires / for knives

(b) (i) poisonous / harms nervous system or brain [1] ignore: harmful (without qualification) (ii) protons → 82 [1] neutrons → 125 [1] (c) (i) Any three of: [3]

sodium goes into a ball / gets smaller / disappears

allow: dissolves ignore: reacts moves (over surface) bubbles / effervescence /

ignore: hydrogen given off floats on the water (as it reacts) / fizzes / hissing / crackling

ignore: sound litmus turns blue /

ignore: changes colour (ii) sodium hydroxide [1] hydrogen [1] (iii) electron [1] Ion [1] gains [1] negative [1] [Total: 15]




3 (a) Any two of: [2] temperature mass / amount of manganese(IV) oxide / volume of manganese(IV) oxide size of manganese dioxide particles allow: pressure ignore: concentration (b) (i) the greater the concentration the greater the speed / rate increases with concentration [1]

ignore: concentration increases speed / more oxygen the grater the concentration (ii) less hydrogen peroxide present (in B) / more hydrogen peroxide (in A) [1] allow: hydrogen peroxide less concentrated (in B) (iii) time taken → 27 (s) [1] allow: 26 (s) volume → 37 (cm3) [1] (c) magnesium → copper → manganese → lead [1] ignore: oxide / oxidation numbers [Total: 7] 4 (a) methane [1] (b) arrangement → random / irregularly arranged / no fixed position [1] proximity → close together / touching [1] motion → random/ sliding over each other / movement not entirely free [1] allow: move slightly (c) (i) arrow at tube at bottom left [1] ignore: direction of arrow (ii)

group of (different) molecules / group of (different) hydrocarbons [1] implication of different molecules

with similar / (particular) range of boiling points / molecules with similar molecular masses or small range of molecular masses [1]

(iii) X → naphtha [1] Y → diesel (oil) [1] (iv) structure of ethane showing all atoms and all bonds [1] (v) 2nd box down ticked (saturated hydrocarbon) [1] [Total: 11]




5 (a) molecule → two or more atoms [1] atom → the smallest part [1] ion → an atom that has become [1] (b) (i) pH 13 [1] (ii) 40 [1] (iii) neutralisation [1] (iv) pH decreases / pH goes from higher to lower pH / suitable reference to pH values e.g.

from pH 12 to pH 8 [1] final pH below 7 / stated value below 7 [1] ignore: gets more acidic (c) Any six of: [6]

bubbles (from the electrodes) solution goes yellow(ish) / solution goes green(ish) hydrogen at cathode chlorine at anode

(hydrogen and chlorine gases produced at wrong electrodes = 1) electrodes are graphite / electrodes are carbon electrodes conducts electricity / electrons move in electrodes hydrogen (ions) go to cathode chloride (ions) go to the anode smell of chlorine electrolyte conducts electricity

ignore: hydroxide ions [Total: 14]




6 (a) as a reducing agent / in the blast furnace / for extracting iron or zinc or other suitable metal / to extract metals / in making lime [1]

(b) (i)

layers can slide over each other [1] both ideas of layers and sliding needed

strong bonding in all directions / covalent bonding in all directions / strong bonding in macromolecules in giant structure [1]

both ideas of type of bonding and giant structure needed (ii) for cutting / drill bits / for drills [1] (c) (i) ammonium sulfate [1] ignore: water / hydrogen (ii) nitrogen [1] (d) one pair of electrons in each overlap area [1] (e) 1st box ticked [1] last box ticked [1] [Total: 9]




7 (a) (i) Any two of: [2] have same general formula / have same pattern of formula / members differ by CH2 group have same functional group have similar chemical properties / prepared by similar methods

allow: same chemical properties not: similar properties

show gradual change in physical properties / show trend in boiling points (ii) H H │ │ H – C – C – O – H │ │ H H allow: OH in place of O – H [1] (b) (i) exothermic and temperature increases / goes from 18 to 37 [1] both: exothermic and temperature increase needed for the mark allow: exothermic because heat is given off (ii) grey / black / grey-black [1] not: brown / purple (c) filter (off zinc); [1] note: second mark dependent on filtration for first mark (let alcohol) evaporate / evaporate (off the alcohol) [1] allow: warm gently (to remove some alcohol) allow: use drying agent ignore: heat unqualified / crystallise reject: residue left to dry (d) (i) ZnI2 [1] allow: 5ZnI2 (ii) 2nd answer ringed (giant ionic) [1] allow: underlined or ticked (e) 1 mark for each product [3] zinc nitrate ammonium nitrate not: ammonia nitrate water (f) add (aqueous) sodium hydroxide (and warm) [1] test gas evolved with red litmus paper/ universal indicator paper [1] litmus paper/ universal indicator paper turns blue [1] note: the 2nd and 3rd marks are dependent on the first mark being correct [Total: 15]





0620 CHEMISTRY









1 (a) (i) lithium oxide / strontium oxide [1] (ii) sulfur dioxide / nitrogen dioxide [1] (iii) aluminium oxide [1] (iv) carbon monoxide [1] accept: correct formulae (b) sulfur dioxide [1] burn (fossil) fuel containing sulfur / volcanoes [1] nitrogen dioxide [1] reaction of nitrogen and oxygen [1] high temperatures / in car engine [1] not: exhaust (c) (i) strontium oxide [1] accept: aluminium oxide (ii) use correct formula [1] cond: charges on ions 6x and 2o around oxygen [1] ignore: electrons around Li 2 (a) (i) (waste gases) from animals [1] decaying vegetation / anaerobic decay [1] accept: decomposition of organic material / natural gas (ii) carbon dioxide [1] water [1] (b) photosynthesis removes carbon dioxide from the atmosphere [1] both respiration and combustion produce carbon dioxide [1] any two of the following: [2]

plants photosynthesis changes carbon dioxide into carbohydrates (burning) of fossil fuels / named fuel / petrol / alkanes respiration by living organisms to obtain energy from carbon–containing compounds comment that the balance between these processes determines the percentage of carbon dioxide




3 (a) (i) bauxite [1] (ii) lowers melting point [1] better conductor / reduces amount of energy needed / reduces cost / more

economic / makes process viable / conserves energy [1] (iii) aluminium more reactive than copper / aluminium higher in reactivity series [1] hydrogen not aluminium formed at cathode [1] (b) Al 3+ + 3e → Al [1] 2O2– → O2 + 4e [2] note: not balanced = 1 oxygen reacts with carbon (anode) to form carbon dioxide / C + O2 → CO2 [1] note: if mark(s) for an electrode reaction are not awarded then allow aluminium ions accept

electrons / are reduced [1] oxide ion loses electrons / is oxidised [1] max 4 (c) (i) protective oxide layer [1] (ii) aluminium low density / light [1] aluminium is a good conductor [1] strength / prevent sagging / allows greater separation of pylons / core made of

steel because it is strong [1] 4 (a) rate of forward reaction equals rate of back reaction [1] concentrations do not change / macroscopic properties remain constant (with time) [1] accept: amounts (b) (i) increase [1] reaction 2 [1] Vr > Vp [1] (ii) same [1] reaction 1 [1] Vr = Vp [1] (iii) decrease [1] reaction 3 [1] Vp > Vr [1] accept: moles of gas / molecules of gas as an alternative to volume




5 (a) (i) rate of reaction decreases / gradient decreases [1] because concentration of bromine decreases [1] reaction stops because all bromine is used up [1] (ii) initial rate greater / gradient greater [1] because bigger surface area / more particles of iron exposed [1]

or: final mass the same [1]

because mass of bromine is the same so the same mass of iron is used [1] (iii) increase / decrease / change rate of stirring / not stirred [1] measure new rate / compare results [1] (b) (i) Fe to Fe2+ [1] because oxidation is electron loss / increase in oxidation number [1] (ii) Fe [1] (c) add sodium hydroxide solution / ammonia(aq) [1] Fe2+ green precipitate [1] Fe3+ brown precipitate [1] 6 (a) (i) correct structural formula of ethanoic acid [1] allow: –OH not: –COOH (ii) correct structural formula of ethanol [1] allow: –OH (b) (i) ethyl ethanoate [1] (ii) –OC6H4COOCH2CH2O– correct ester linkage [1] correct repeat units [1] continuation [1] accept: boxes if it is clear what the box represents (iii) any two from: long time to decay landfill sites visual pollution / litter danger to animals poisonous gases when burnt [2] accept: any correct suggestion




(c) synthetic – only two monomers [1] protein – many different monomers [1] or: protein has 1 C=O and 1N–H [1] nylon has 2 C=O / 2N–H [1] or: synthetic – one monomer is a dicarboxylic acid and the other is a diamine [1] protein all monomers are amino acids [1] 7 (a) (i) any Group 1 metal [1] accept: LiOH (ii) Cu(OH)2 → CuO + H2O [2] note: products only = 1 (iii) reactivity of metals / metals have different reactivities [1] (b) (i) zinc oxide, nitrogen dioxide, oxygen [2] note: two correct = 1 (ii) 2KNO3 → 2KNO2 + O2 [2] note: unbalanced = 1, correct word equation = 1 (c) calculation: Mr for NaHCO3 = 84 g; Mr for Na2O = 62 g; Mr for NaOH = 40 g Mr for Na2CO3 = 106 g (i) number of moles of NaHCO3 used = 3.36/84 = 0.04 [1] (ii) if residue is Na2O, number of moles of Na2O = 2.12/62 =0.034 / 0.03 if residue is NaOH, number of moles of NaOH = 2.12/40 = 0.053 / 0.05 if reside is Na2CO3, number of moles of Na2CO3 = 2.12/106 =0.02 all three correct [2] note: two correct = 1 (iii) equation 3 [1] mole ratio 2:1 agrees with equation [1]





0620 CHEMISTRY









1 (a) 27p 32n 27e [1] 27p 32n 25e [1] (b) (i) same proton number / same number of protons / same atomic number [1]

different nucleon number / different number of neutrons / different mass number [1] (ii) same electron distribution [1] allow: same proton number and same number of electrons not: same number of electrons / same number of shells (iii) industrial detection of leaks / thickness of paper etc. / nuclear fuel for generating

electricity / nuclear weapons / radiographs of welds / measuring wear / sterilising food [1] not: carbon dating

medical treatment of cancer, radiotherapy, treatment of thyroid gland, X rays, tracer studies in body, sterilising equipment, locating tumours

accept: X-rays only once [1] 2 (a) burns to form sulfur dioxide [1] acid rain / any problem associated with acid rain / sulfur dioxide is poisonous [1] (b) (i) bigger surface area [1] burns / reacts faster / greater number of collisions [1] not: more sulfur dioxide (ii) kills microbes / bacteria / fungi etc. [1] accept: anti-oxidant / stops oxygen oxidising juice / prevents growth of bacteria (iii) bleach / refrigerant / making wine / fumigant /insecticide / dyes [1] not: making sulfuric acid (c) 2SO2 + O2 � 2SO3 [1] temperature 400 to 450

oC [1] pressure 1 to 10 atmospheres [1] catalystvanadium(V) oxide / vanadium oxide [1] (d) SO3 + H2SO4 � H2S2O7 [1] H2S2O7 + H2O � 2H2SO4 [1]




3 (a) (i) heat / roast in air / oxygen [1] accept: burn in air / oxygen (ii) (reduce) with carbon / carbon monoxide [1]

(b) test it with both hydrochloric acid and sodium hydroxide(aq) [1] accept: any named strong acid and any strong alkali if only acid and alkali given then max = 3 basic oxide reacts with acid [1] acidic oxide reacts with alkali/base [1] amphoteric reacts with both [1] accept: for react – form salt and water

(c) (i) at equilibrium [1]

rate of forward reaction equals rate of back reaction / concentrations remain constant / macroscopic properties do not change with time [1] accept: amounts do not change with time

(ii) equilibrium moves to left (SbOCl used up) [1]

hydrochloric acid removed by reacting with SbOCl precipitate dissolves in hydrochloric acid

(iii) add water / dilute / add an alkali / add more SbCl3 / add a base / add a carbonate [1] 4 (a) (i) ScF3 [1]

correct charges [1] 7o and 1x around fluorine [1]

(ii) strong forces / bonds between ions [1]

accept: lattice as alternative to bonds / requires a lot of energy to break bond between ions not: giant molecular / IMFs (b) (i) 1Si surrounded by 4O [1] 1O surrounded by 2Si [1] looks or stated to be tetrahedral [1] (ii) silicon(IV) oxide does not conduct and (molten) scandium fluoride

does conduct [1] not: good and poor (iii) scandium fluoride contains ions (silicon(IV) oxide does not) [1]

ions can move when molten or in solution [1]




5 (a) CH3-CH2-CH2-CH2-CH2-OH [1] 88 [1] 156 to159

oC [1] (b) any two from: (same) general (molecular) formula

same functional group consecutive members differ by –CH2 common methods of preparation

(c) correct structure and 4bp around carbon [1] 2bp and 2nbp around oxygen [1] 1bp on hydrogens [1] (d) (i) correct structural formula for propanoic acid [1] allow: OH but all other bonds to be shown (ii) air / oxygen [1] bacteria / microbes / micro-organisms [1] accept: mother of vinegar not: yeast (e) propyl ethanoate [1] allow: CH3COOC3H7 not: C5H10O2 [1]




6 (a) (i) to neutralise all the acid / so all acid reacts [1] not: reaction goes to completion (ii) remove excess carbonate / removes unreacted carbonate [1] not: remove solid (iii) need water of crystallisation / hydrated crystals / to get crystals [1] (iv) filter / decant / wash crystals [1] dry with filter paper or tissues etc. [1] accept: in warm oven / warm place / in sun not: just heat

(b) (i) potassium carbonate is soluble / both salts soluble [1] (ii) use potassium carbonate solution [1] accept: implication of solution – in pipette / burette / 25 cm3 titrate / titration term required [1] use an indicator accept: any named acid/base indicator [1] repeat without indicator / use carbon to remove indicator [1] (c) mass of hydrated magnesium sulfate = 1.476 g

mass of barium sulfate formed = 1.398 g the mass of one mole of BaSO4 = 233 g the number of moles of BaSO4 formed = 0.006 [1] the number of moles of MgSO4.xH2O used in experiment = 0.006 [1] the mass of one mole of MgSO4.xH2O = 1.476/0.006 = 246 g [1] the mass of xH2O in one mole of MgSO4.xH2O = 246 – 120 = 126 g [1] x = 126/18 = 7 [1] if x given without method = max 1 note: apply ecf but x must be an integer and less than 10




7 (a) fraction is the distillate collected [1] between 40–100

oC / in the stated range [1] (b) (i) C8H18 + 25/2O2 � 8CO2 + 9H2O [2]

accept: double the above / 12.5 in front of oxygen

(ii) poisonous / toxic / damages health / brain / kidneys [1] note: must relate to people

not: just harmful (iii) dibromo 2 bromine atoms (per molecule)

not: Br2

accept: 2 bromide groups eth 2 carbon atoms (per molecule)

ane a C-C single bond / no C=C / group CnH2n+1 / saturated ignore: any reference to alkanes all three correct [2] two correct only [1] [2]

(iv) position of bromine atom(s) [1]

(c) 0.104/0.026 [1]

n = 4 [1]

(d) (oxides of nitrogen) change carbon monoxide into carbon dioxide [1] oxides of nitrogen then become nitrogen [1] (oxides of nitrogen) change hydrocarbons into carbon dioxide and water [1] accept: balanced equations for first two marks

2NO + 2CO � N2 + 2CO2 and 2NO � N2 + O2 [2] oxygen changes hydrocarbons into carbon dioxide and water [1]





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1 (a) (i) Cs / Fr [1] (ii) Br [1] (iii) U / Pu / Th [1]

(iv) I or At [1] (v) As [1] (vi) He / Ne / Ar / Kr / Xe [1] (b) (i) GeO2 / GeO [1] (ii) TeBr2 / TeBr4 [1] (c) (i) Sr2+ [1]

(ii) F– [1] 2 (a) (i) molecule / unit / simple compound / building block and used to make a

polymer / big molecule / long chain / macromolecule [1] formation of a polymer / big molecule / long chain / macromolecule or joining of

monomers and elimination / removal / formation of a simple or small molecule / H2O / HCl [1]

note: two points needed for 1 mark in both parts (ii) -O- linkage [1] three correct monomer units [1] continuation [1] (b) (i) catalyst and from living organism [1] accept: biological catalyst / protein catalyst (ii) enzyme denatured / destroyed [1] (iii) chromatography [1] locating agent / description of locating agent [1] measure Rf / compare with standards [1]




3 (a) sodium hydroxide solution [1] warm [1] (only) ammonium phosphate gives off ammonia / gas (which will turn red litmus paper

blue) [1] or: sodium hydroxide solution [1] dissolve fertiliser in water [1] Ca2+ gives (white) ppt [1] or: flame test [1] Ca2+ brick red / orange / orange-red [1] NH4

+ no colour [1] (b) iron catalyst [1] pressure 150–300 atmospheres [1] temperature 370–470 °C [1]

N2 + 3H2 ⇌ 2NH3 [1]

note: units required for temperature and pressure (c) potassium / K [1] (d) (i) needs to be soluble / in solution (to be absorbed by plants) [1] (ii) base [1] proton acceptor [1] (e) plant growth depends on soil acidity or pH / plants have optimum pH (for growth) [1] add Ca(OH)2 / CaO / CaCO3 / lime / slaked lime / quicklime / limestone [1] 4 (a) (i) alloy / mixture [1] iron and carbon / another metal or element etc. [1] (ii) electron loss [1] (b) electrons move from / lost from Mg [1] to steel / iron [1] (c) (i) 2H+ + 2e → H2 [2] not balanced = 1




(ii) sacrificial protection – is a cell [1] cathodic protection – is electrolysis NOT electrical cell [1] or: sacrificial protection – electrons from more reactive metal [1] cathodic protection – electrons from battery etc. [1] or: sacrificial protection – does not need or use power / battery / electricity / electrical

cell [1] cathodic protection – does [1] or: sacrificial protection uses up / needs a sacrificial / more reactive metal [1] cathodic protection doesn’t [1] 5 (a) light / UV / sun / sunlight / solar energy [1] starts / initiates / speeds up [1] (b) (i) 0.03 % – 1(%) carbon dioxide [1] accept: less than 1(%) 20 % – 21(%) oxygen [1] (ii) remove carbon dioxide from atmosphere [1] produce oxygen [1] any two from: photosynthesis chlorophyll / chloroplast light / sun / sunlight / UV / photochemical formed carbohydrates / glucose / sugar(s) [2] (c) reaction is photochemical / needs light [1] (light) causes formation of silver / silver ions reduced [1] (on formation of silver) goes black [1] no light still silver(I) bromide / stays white / no reaction [1] 6 (a) any three from: barium more reactive / forms ions more readily barium reacts with (cold) water, nickel does not barium more vigorous with acids nickel compounds coloured, barium compounds white nickel has more than one oxidation state, barium has one nickel / nickel compounds catalysts, barium / barium compounds not catalysts nickel forms complex ions, barium does not [3] (b) (i) forward reaction favoured by low temperatures / reverse reaction favoured by

high temperatures / heat [1] exothermic [1] (ii) products / RHS [1] has fewer moles / molecules / smaller volume / ORA [1] (iii) do not react or left behind / left at 60

oC [1]




(iv) electrolysis [1] cathode (pure) nickel [1] anode impure nickel [1] electrolyte is a soluble nickel salt [1] 7 (a) correct method shown

i.e. 126/14 (= 9) or 14x = 126 or x = 9 or (12 × 9) + 18 = 126 [1] C9H18 note: correct formula only = 1 [1] (b) (i) all hydrogen atoms 1bp [1] C—C bond atoms 1bp [1] C=C 2 bp [1] (ii) correct repeat unit [1] continuation [1] (iii) bonds broken H-H +436 (kJ/mol) C=C +610 = +1046 (kJ/mol) [1] bonds formed

2C-H –415 × 2 kJ/mol C-C –346 = –1176 (kJ/mol) [1] –130 kJ/mol / more energy released than absorbed [1] or: bonds broken 3882 (kJ/mol) [1] bonds formed 4012 (kJ/mol) [1] –130 kJ/mol / more energy released than absorbed [1] allow: ecf for final mark as long as the answer is not positive note: units not necessary (c) (i) butan-1-ol or butan-2-ol or butanol [1] (ii) CH3-CH2-CH(Br)-CH2Br [2] C4H8Br2 = 1 note: any other dibromobutane = 0

(iii) HI [1]





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1 (a) table of results for experiment 1 initial temperature boxes completed correctly for 0.0, 0.5 and 1.0 min (1) other temperature boxes correctly completed ascending (1) comparable to supervisors (1) [3] (b) table of results for experiment 2 initial and final temperature boxes completed correctly for 0.0, 0.5 and 1.0 min (1) other temperature boxes correctly completed ascending (1) comparable to supervisors (1) [3] (c) all points correctly plotted (3), –1 for any incorrect best fit smooth line graphs (1) labels (1) [5] (d) value from graph (1) unit (1) shown clearly (1) [3] (e) exothermic / redox / displacement (1) [1] (f) (i) temperature rises greater / faster in experiment 1 or converse (1) (ii) zinc is more reactive (1) [2] (g) temperature changes would be larger / faster / owtte (1) less solution (1) [2] (h) solid would react slower / temperature rises would be slower (1) smaller / less surface area (1) [2] [Total: 21] 2 (a) (i) P colourless no smell Q colourless no smell R colourless smells acidic/vinegar all colours correct (1) correct smells (1) [2] (ii) P red pH 1–3 Q green pH 6–7 R orange pH 4–5 all colours correct (1) pH values correct order (1) [2] (b) P fizzes / effervescence (1) lighted splint (1) pops (1) [3] Q no reaction (1) R fizzes (1) [2]




(c) P effervescence / fizz / bubbles (1) Q no reaction (1) R fizzes (1) [3] (d) blue colour (1) [1] white precipitate (1) [1] (e) 98–102 (1) [1] (f) sulfuric (1) acid (1) [2] (g) water (1) [1] (h) organic / weak / ethanoic / acid (1) [1] [Total: 19]





0620 CHEMISTRY









1 (a) table of results for experiment 1 all boxes completed correctly (1) readings to 1 d.p. (1) comparable to supervisors (1) ± 3 cm3 [3] (b) table of results for experiment 2 all boxes completed correctly (1) readings to 1 d.p. (1) comparable to supervisors (1) ± 3 cm3 [3] (c) red / brown (1) [1] (d) blue / black (1) not: purple to colourless (1) not: clear [2] (e) as an indicator / to test for iodine / owtte (1) [1] (f) (i) experiment 2 (1) [1] (ii) experiment 2 is 2× volume of experiment 1 (1) allow: almost double [1] (iii) solution F more concentrated / stronger (1) or converse twice / double (1) [2] (g) half value from table result for experiment 1 (1) half volume of potassium iodate/iodine (1) [2] (h) (i) two sources of error e.g. using a measuring cylinder to measure iodate/acid experiment only carried out once going past end point / owtte not: references to human error / temperature / rinsing [2] (ii) two meaningful improvements related to above e.g. use a pipette / burette repeat experiment [2] [Total: 20] 2 (a) (i) liquid H blue and no smell (1) any reference to smell = 0 pH < 7 (1) [2] (ii) liquid J colourless (1) not: clear sweet smell / petrol / acetone / owtte (1) not: pungent / strong two layers / immiscible (1) with indicator paper pH 7 or green (1) [4]




(b) white precipitate (1) [1] (c) (i) blue (1) precipitate (1) on heating black (1) [3] (ii) blue precipitate (1) dissolves / solution (1) deep / royal blue (1) [3] (d) (i) extinguished / goes out / no reaction (1) not: no change / nothing happens [1] (ii) flame / catches fire (1) orange / yellow (1) smokey / sooty (1) max 2 orange / yellow or smokey / sooty flame = (2) reference to glowing splint = 0 [2] (e) copper (1) sulfate (1) acidic (1) water present / aqueous (1) max 2 [2] (f) organic (1) hydrocarbon / non polar (1) allow: flammable / fuel / alkane not: alcohol [2] [Total: 20]





0620 CHEMISTRY









1 (c) table of results initial readings completed correctly (1) final readings completed correctly (1) all readings to 1 d.p. (1) differences completed correctly (1) comparable to supervisors (2) [6] (d) pink (1) to colourless (1) not: clear [2] (e) neutralisation / exothermic (1) [1] (f) (i) C/3 smallest B/2 largest (1) one correct = 1 [1] (ii) order is C/3 A/1 B/2 (2) one correct = 1 [2] (g) experiment 2 is twice the volume of experiment 1 or converse (1) [1] (h) twice value from table result for experiment 3 (1) cm3 (1) [2] (i) use a pipette / burette [1] (j) effect none / owtte (1) reason no change in concentration / temperature has no effect on quantities or moles / only

affects speed (1) [2] (k) any correct method that would work – precise details not needed using same method with different acids = 0 reagents (1) method (1) result (1) [3] e.g. to sodium hydroxide add named acid (1) measure temperature change (1) largest change = strongest / more concentrated solution (1) e.g. to sodium hydroxide add named (excess)metal salt solution (1) filter precipitate (1) largest mass = strongest / more concentrated solution (1) [Total: 21] 2 (a) (i) yellow / brown / orange (1) [1] (ii) white / colourless (1) [1]




(b) (i) no change / no reaction owtte (1) [1]

(ii) white (1) precipitate (1) [2] (iii) brown (1) precipitate (1) [2] (iv) brown precipitate (1) [1] (c) (i) solid white (1) condensation at top of tube (1) limewater / blue litmus (1) milky / red (1) max 3 [3] fizz / bubbles / effervescence (1) [1] (ii) fizz / bubbles / effervescence / brown precipitate (1) [1] (d) iron (1) (III) (1) chloride (1) [3] (e) carbon dioxide (1) [1] (f) carbonate / hydrogen carbonate (1) non transition metal / named metal e.g. sodium (1) [2] [Total: 19]





0620 CHEMISTRY









1 (a) (i) (gas) syringe (1) [1] (ii) arrow indication under copper (1) [1] (b) spatula (1) [1] (c) black (1) [1] (d) to return to room/initial temperature (1) correct volume of gas (1) [2] 2 (a) points plotted correctly (2) smooth line graph missing anomalous point (1) [3] (b) point at 15 cm3/pH 2.6/third point (1) [1] (c) (i) 12.6 (1) [1] (ii) pH 1 (1) extrapolation shown (1) [2] (d) (i) 7 (1) [1] (ii) 25 (1) [1] (e) repeat experiment (1) stop when 25 cm3 added/when pH7 (1) evaporate/heat (1) use same volumes (1) to crystallising point/until saturated (1) max [3] 3 (a) chromatography (1) [1] (b) line drawn on diagram below origin (1) [1] (c) does not interfere with results/owtte (1) [1] (d) difference A has more/3 colours/B has less/2 colours/B contains F but A doesn’t/A contains C/ D but B does not (1) similarity both contain same colour/E (1) [2]




(e) C, D and E (1) [1] 4 (a) Table of results for Experiment 1 temperature boxes completed correctly (3) 20, 21, 21, 32, 39, 42, 44, 45, 45 [3] (b) Table of results for Experiment 2 temperature boxes completed correctly (3) 20, 21, 21, 24, 32, 36, 37, 38, 38 [3] (c) all points correctly plotted (3) -1 for each incorrect best fit smooth line graphs (1) labels (1) [5]

(d) value from graph ≈28oC ± half small square (1) unit (1) shown clearly (1) [3] (e) exothermic/redox/displacement (1) [1] (f) (i) temperature rises greater/faster in Experiment 1 (1) allow converse [1] (ii) zinc is more reactive (1) [1] (g) temperature changes would be same/faster/owtte (1) metal in excess (1)/ temperature changes would be greater (1) lower volume (1) [2] (h) solid would react slower/temperature rises would be slower (1) smaller surface area (1) [2] 5 (a) (i) P colourless, no smell (1) [1] (ii) P pH 1–3 (1) [1] (b) P fizzes/effervescence/bubbles (1) lighted splint pops (1) not hydrogen [2] (c) white (1) precipitate (1) [2] (e) weak acid (1) ethanoic acid (2) [2] (f) water (1) [1]




6 measured volume of seawater (1) using measuring cylinder (1) into evaporating dish/beaker (1) pre-weighed (1) evaporate/heat (1) to dryness/constant mass (1) re-weigh (1) indication of calculation method (1) max [6] would not work = max 0 [Total: 60]





0620 CHEMISTRY









1 (a) (i) water/H2O inserted into box (1) [1] (ii) two arrows underneath magnesium and wool (1) [1] (b) magnesium oxide (1) [1] (c) lighted splint (1) pops (1) [2] glowing splint pops = 1 (d) highly/very exothermic reaction/high temperature reached/suck back of water/owtte (1) [1] 2 (a) Table of results volumes correct (3) -1 for each incorrect 0, 17, 25, 40, 48, 54, 57 [3] (b) points plotted correctly (3) -1 for each incorrect smooth curve missing anomalous point (1) [4] (c) (i) at 2 min (1) [1] (ii) from graph ± half small square 30 cm3 (1) indication on grid (1) [2] (d) (i) decreases/slows down (1) not stops [1] (ii) hydrochloric acid used up/hydrochloric acid becomes less concentrated (1) [1] not reactants used (e) (i) sketch curve to left of original (1) ignore if level is above original [1] (ii) sketch curve to right and below original (1) [1] 3 (a) to speed up the reaction/owtte (1) not reacts easily [1] (b) excess cobalt carbonate/base used (1) [1] (c) metal could react/glass does not react/owtte (1) [1] (d) solid/cobalt chloride visible/no more fizzing/no more gas (CO2) produced (1) [1] ignore colour change (e) crystals forming (on glass rod/on edge) (1) [1]




(f) anhydrous cobalt chloride formed/water/steam removed/powder formed (1) turn blue (1) [2] 4 (a) Table of results for Experiments 1 and 2 initial boxes completed correctly 0.0, 2.0 (1) (b) final boxes completed correctly 23.0, 48.0 (1) differences correct 23.0, 46.0 (1) allow ecf readings to 1 dp (1) [4] (c) to remove impurities/solution F/owtte (1) [1] (d) as an indicator/to show presence of iodine/owtte (1) [1] (e) (i) Experiment 2 (1) [1] (ii) Experiment 2 2x volume Experiment 1 [1] (iii) solution F more concentrated/stronger (1) allow converse 2x as concentrated (2) [2] (f) half value from table result for Experiment 1, 11.5 (1)

half volume of potassium iodate/iodine/23

2 (1) [2]

(g) (i) two sources of error (2) e.g. experiment only done once/using a measuring cylinder to measure iodate/ acid going past end point/owtte [2] ignore reference to temperature or human error (ii) two meaningful improvements related to above (2) e.g. use a pipette/burette/add smaller volumes e.g. 0.5 cm3/repeat experiment [2] 5 (a) (i) blue (1) [1] (b) white (1) precipitate (1) [2] (c) (i) blue (1) precipitate (1) [2] (ii) blue precipitate (1) dissolves/solution (1) deep/royal blue (1) [3] (e) organic (1) hydrocarbon / flammable / fuel (1) [2]




6 (a) litmus paper/pH paper (1) blue/8–10 (1) test for NH4

+ using NaOH = 0 correct chemical test and result e.g. Cu2+ could score 2 marks [2] (b) 25 cm3 of Kleen Up in flask/beaker (1) not test-tube nitric acid in burette (1) add indicator (1) no indicator = max 2 add/titrate acid (1) until neutral/owtte (1) note volume acid (1) calculate concentration (1) max [5] [Total: 60]





0620 CHEMISTRY

0620/63 Paper 6 (Alternative to Chemistry), maximum raw mark 60








1 (a) funnel (1) stirrer/glass rod (1) evaporating dish (1) [3] (b) filtration (1) [1] (c) C/A (1) [1] 2 (a) temperatures correctly recorded (3) -1 for each incorrect 25, 41, 44, 29, 31 temperature rises correct (1) 0, 16, 19, 4, 6 [4] (b) appropriate scale for y axis (1) note must be greater than half of grid bars correct heights (2) plotting final temps = max 2 bars labelled correctly (1) no bar chart = max 1 [4] (c) (i) calcium (1) [1] (ii) no temperature rise (1) no reaction/unreactive (1) not low/less reactive [2] (d) correct order of reactivity (2), two in wrong order (1) [2] least copper iron zinc magnesium most calcium (e) temperature changes/rises would be less/lower/half (1) more acid/volume (1) [2] 3 (a) smooth curve missing anomalous points (1) [1] (b) at 20 oC (1) [1] (c) decreases (1) [1] (d) line sketched below original curve (1) [1] 4 (c) Table of results initial readings completed correctly 0.0, 1.9, 11.1 (1) final readings completed correctly 10.4, 22.7, 16.3 (1) all readings to 1 dp (1) differences completed correctly 10.4, 20.8, 5.2 (1) [4]




(d) pink (1) to colourless(1) not clear [2] (e) neutralisation/exothermic (1) [1] (f) (i) C/3 smallest, B/2 largest (1) [1] (ii) order is C/3, A/1, B/2 (2) one correct = 1 [2] (g) Experiment 2 2x volume Experiment 1 or converse (1) [1] (h) 10.4 (1) cm3 (1) allow ecf from (c) [2] (i) use a pipette/burette [1] (j) no effect/owtte (1) no change in concentration/temperature has no effect on quantities/only affects speed (1) [2] (k) any correct method that would work – precise details not needed same method using different acids = 0 reagents (1) method (1) result (1) [3] e.g. to sodium hydroxide add named acid (1) measure temperature change (1) largest change = strongest/more concentrated solution (1) to sodium hydroxide add named (excess) metal salt solution (1) filter precipitate (1) largest mass = strongest/more concentrated solution (1) 5 (a) (i) yellow/brown/orange (1) [1] (b) (i) no change/no reaction/owtte (1) [1] (ii) white (1) precipitate (1) [2] (iii) brown (1) precipitate (1) [2] (iv) brown precipitate (1) [1] (d) carbon dioxide (1) [1] (e) carbonate/hydrogen carbonate (1) non transition metal/named metal e.g. sodium (1) [2]




6 (a) substance/liquid that dissolves/owtte (1) [1] (b) (in)flammable/catches fire easily (1) [1] (c) fractional distillation (1) [1] (d) chromatography (1) apply spot of oil to paper (1) use of solvent (1) description of process (1) results (1) max [4] [Total: 60]

CAMBRIDGE INTERNATIONAL EXAMINATIONS


MARK SCHEME for the October/November 2012 series

0620 CHEMISTRY


Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2012 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.




© Cambridge International Examinations 2012

Question Number

Key Question Number

Key

1 C 21 C

2 B 22 C

3 C 23 D

4 B 24 C

5 A 25 B

6 B 26 A

7 A 27 A

8 D 28 A

9 A 29 D

10 D 30 A

11 D 31 D

12 D 32 B

13 B 33 C

14 A 34 D

15 C 35 C

16 B 36 A

17 C 37 C

18 D 38 A

19 D 39 C

20 B 40 A




0620 CHEMISTRY







Question Number

Key Question Number

Key

1 C 21 B

2 C 22 C

3 B 23 B

4 A 24 D

5 B 25 C

6 A 26 A

7 B 27 A

8 D 28 A

9 D 29 A

10 A 30 D

11 D 31 D

12 A 32 C

13 D 33 B

14 B 34 D

15 C 35 A

16 C 36 C

17 D 37 C

18 B 38 C

19 D 39 A

20 C 40 A




0620 CHEMISTRY







Question Number

Key Question Number

Key

1 C 21 D

2 B 22 C

3 C 23 D

4 A 24 C

5 A 25 B

6 B 26 D

7 A 27 A

8 D 28 B

9 A 29 A

10 D 30 A

11 D 31 D

12 D 32 C

13 D 33 B

14 C 34 A

15 C 35 C

16 C 36 D

17 C 37 C

18 D 38 A

19 D 39 B

20 A 40 C




0620 CHEMISTRY








1 (a) (i) C / C2H4 / ethene; [1] (ii) A / CO2 / carbon dioxide; [1] (iii) E / ethanol / correct formula for ethanol; [1] (iv) D / CH4 / methane; [1] (v) A / CO2 / carbon dioxide; [1] allow: E (vi) E / ethanol / correct formula for ethanol; [1] allow: A (b) C2H4; [1] (c) compound: substance containing two or more different atoms joined / bonded

together / substance containing 2 or more elements that can only be separated by chemical means; [1]

allow: different atoms joined / different elements joined / 2 elements react to form a molecule / molecule with 2 or more elements / substances chemically combined

ignore: two or more molecules combined / different elements react / substances made up of molecules

reject: if reference to a mixture inert: unreactive / doesn’t react; [1] catalyst: substance which speeds up a reaction / it speeds up a reaction; [1] allow: changes rate of reaction / changes speed of reaction [Total: 10] 2 (a) structure completely correct;; [2] allow: 1 mark for 1 pair of electrons bonded between H and Cl; ignore: inner shell electrons (b) (i) A: burette; [1] B: flask / erlenmeyer; [1] (ii) pH starts above 7 / stated value above 7; [1] allow: high pH decreases (on addition of acid); [1] (pH) ends at below 7 / stated value below 7; [1] allow: low pH note: pH decreases to pH 7 = 2 marks note: pH goes from alkali to acid = 1 mark




(iii) ammonium chloride; [1] reject: ammonia chloride NH3; [1] (c) any 4 of: [4] blue solution at start / precipitate formed / (light) blue (precipitate) / precipitate redissolves (in excess ammonia) / solution formed (in excess ammonia) /

precipitate disappears (solution is) deep blue / dark blue allow: goes deep blue / dark blue / goes darker blue [Total: 13] 3 (a) (i) magnesium → zinc → iron → lead / Mg > Zn > Fe > Pb;; [2] if: one pair reversed / complete order reversed = 1 mark (ii) no / it will not react and zinc is more reactive / iron is less reactive; [1] ignore: zinc is reactive / iron is unreactive (b) 1st box ticked; [1] last box ticked; [1] (c) (i) arrangement: regular / fixed pattern / any indication of regularity e.g. in layers; [1] allow: close together / packed together ignore: stick together / all together motion: cannot move / fixed in position/ (only) vibrate; [1] ignore: only move a little / move (ii) any three of: [3] dissolve sodium chloride / add water / filtration / use a filter paper / sand remains on filter paper / ignore: residue on filter paper salt solution goes through (filter paper) / salt solution is the filtrate / salt water goes into

the collecting tube allow: decanting for 1 mark (in place of filtration) ignore: water goes through ignore: distillation (d) distillation; lower; volatile; condenser; vapour; (1 mark each) [5] [Total: 15]




4 (a) atoms with same number of protons but different number of neutrons; [1] allow: atomic number for number of protons allow: different mass number / nucleon number for different number of neutrons allow: same (type of) atom with different mass numbers ignore: atoms with different numbers of neutrons ignore: element(s) with different numbers of neutrons ignore: atoms with different relative atomic mass (b) any 5 of: [5] nucleus (need not be labelled) in middle of atom and electrons round outside (electrons can

be shown as dots, crosses or e) / protons in nucleus – labelled or shown by + or p / 3 (protons) / neutrons in nucleus – labelled or shown by n / 4 (neutrons) / 3 electrons – labelled or shown by dots, crosses or e / 2 electrons in first shell and 1 in second (c) 4Li + O2 → 2Li2O ;;; [3] allow: two marks for 2Li + O → Li2O / 4Li + 2O → 2Li2O allow: 1 mark for O2 if no other marks scored (d) (i) electrolyte correctly labelled; [1] anode rod correctly labelled; [1] ignore: label on circuit / label on + sign (ii) dissolved in water / solution in water; [1] allow: answers implying substance is mixed with water ignore: hydrated / hydrous (iii) ions can move; [1] allow: ions are free reject: electrons can move [Total: 13] 5 (a) hydrogen → a fuel with RMM of 2; [1] methane → the main constituent of natural gas; [1] fuel oil → fuel for ships; [1] kerosene → fuel for aircraft; [1] (b) (i) amount or mass or volume of water / distance of flame from can / height of flame / same

can; [1] ignore: the water (unqualified) / same amount of fuel / time (ii) to make sure that the water has the same temperature (throughout) / it is at the same

temperature / so it is heated evenly / so there are no hot spots / so there are no cold spots; [1]

allow: so that all the particles are heated ignore: so that particles mix




(iii) petroleum spirit; [1] highest temperature rise / highest increase in temperature; [1] allow: calculation of all the temperature differences form the table ignore: because it releases most heat / because it has the highest temperature if fuel incorrect = 0 for the question (c) A = nitrogen / N2 / N; [1] B = oxygen / O2 / O; [1] (d) (i) lamps / (to provide an) inert atmosphere / in welding / lasers etc [1] allow: for lighting ignore: for neon lights (ii) 3 / third / III; [1] (iii) inert / unreactive; [1] ignore: it is stable [Total: 13] 6 (a) any 4 of: [4] crystals dissolve or go into solution / diffusion / random movement of ions or named particles (can be atoms or ions or particles or

molecules) / particles move everywhere / particles spread out / particles mix both ions and water in constant movement / particles collide / particles react / ions react / atoms react Ag ions and iodide ions (react) / (to make) precipitate of silver iodide / ignore: particles move (unqualified)

(b) 2KI + Cl2 → 2KCl + I2 ; [2]

allow: 1 mark for 2KI + 2Cl → 2KCl + I2 ; [Total: 6] 7 (a) 24; [1] (b) 256; [1]




(c) any 4 of: [4] coal / petroleum / crude oil / named fraction from crude oil sulfur reacts with oxygen / air (sulfur burns) to form sulfur dioxide ignore: sulfur oxide sulfur dioxide reacts (with gases) in the atmosphere / sulfur dioxide reacts with oxygen /

nitrogen oxides to form sulfur trioxide sulfur dioxide / trioxide react with water / rain allow: sulfur dioxide / trioxide dissolves in water / rain allow: sulfur oxide(s) mix with water / rain (to form) sulfurous/ sulfuric acid (d) nitrogen / N2 / N; phosphorus / P; [2] (e) add (acidified) barium chloride / barium nitrate; [1] white precipitate; [1] note: second mark dependent on correct reagent [Total: 10]




0620 CHEMISTRY








1 (a) (i) D / phosphorus / P; [1] (ii) E / helium / He; [1] (iii) C / chlorine / Cl2 / Cl; [1] (iv) A / copper / Cu; [1] (v) A / copper / Cu; [1] (b) C; D; [2] (c) giant; covalent; [2] (d) substance containing only 1 type of atom / substance which cannot be broken down into a

simpler one; [1] allow: substance which can’t be separated by chemical means ignore: substance with one atom / substance with similar types of atom [Total: 10] 2 (a) (damp) red litmus (paper); [1] turns blue; [1] note: second mark dependent on correct reagent allow: universal indicator (1 mark); turns blue / purple (1 mark) allow: 1 mark for litmus paper turns blue / pH paper turns blue allow: white fumes (1 mark); with hydrochloric acid vapour (1 mark) ignore: other chemicals added as long as it is clear that ammonia is the gas being tested (b) pH 9; [1] (c) (i) NH4Cl on right; [1] (ii) structure completely correct;; [2]

allow: 1 mark for 1 pair of electrons bonded between H and Cl ignore: inner shell electrons




(d) (i) any 4 of: [4] use of burette add indicator to flask add acid to alkali (or vice versa)

until indicator changes colour record volume (of acid or alkali added) ignore: amount of acid or alkali added

repeat without indicator using same volume of acid and ammonia as in previous experiment (ii) heat to crystallisation (point) / evaporate some of the water / leave to crystallise [1] allow: heat then cool ignore: heat (unqualified) / heat to dryness / heat to get rid of all the water [Total: 11] 3 (a) (i) get darker / deeper colour; [1] (ii) gas; [1] allow: answer written in table (iii) any value between –180 to –20 °C (actual = –101 °C); [1] allow: answer written in table (b) (i) chlorine → bromine → iodine → astatine;; [2] allow: 1 mark if one pair incorrect way round / order completely reversed (ii) no and chlorine is more reactive (than bromine) / bromine is less reactive; [1] ignore: chlorine is very reactive / bromine is not very reactive ignore: chloride is more reactive (c) H2O (on right); [1] 2 on left (this is dependent on H2O being the product); [1] (d) (i) to kill bacteria / to kill microbes / to disinfect it [1] allow: to kill germs / to get rid of bacteria ignore: to clean water (ii) any two of: [2] minerals or (dead) remains insoluble in water these particles are large / water particles (molecules) are very small

(larger particles) get stuck (between the sand particles) / (larger particles) remain in the sand / trapped by sand

water (molecules) drain through / water comes out the bottom ignore: water is filtered [Total: 11]




4 (a) groups of hydrocarbons / molecules; [1] with similar (range of) boiling points / sizes / masses; [1] allow: 1 mark for idea of separating molecules for particular fuels ignore: petroleum broken down / smaller molecules formed / mixture of fuels (b) (i) gasoline; diesel; [2] (ii) refinery gas: heating / cooking; [1] allow: fuel bitumen: roads / roofing; [1] (c) high temperature; [1]

allow: heat / stated temperature of 200 °C or more catalyst; [1] ignore: name of catalyst ignore: pressure (d) (i) substance containing hydrogen and carbon only; [1] (ii) C4H8 / 2C2H4; [1] (e) (i) H H [1] │ │ C = C │ │ H H (ii) monomers; addition; polymers; [3] [Total: 14]




5 (a) any two of; [2] Al has low density / iron has high density allow: lightweight or light for density) Al does not form coloured compounds / iron formed coloured compounds Al has only one oxidation state / iron has several oxidation states Al does not act as a catalyst / iron can act as a catalyst Al is softer / iron is harder (comparative needed) Al has lower density / iron has higher density (comparative needed)

Al is a better conductor / iron is not as good a conductor (comparative needed) Al is weaker / iron is stronger (comparative needed) ignore: melting and boiling points (b) any suitable use e.g. aircraft or car (bodies) / food containers / pots and pans / electrical wiring / drinks cans; [1] (c) precipitate formed; [1] which is white in colour; [1] dissolves (in excess sodium hydroxide); [1] allow: precipitate disappears [Total: 6] 6 (a) (i) limestone / chalk; [1] (ii) the other product is a gas / carbon dioxide escapes; [1] allow: carbon dioxide is a gas / waste gases are gone / CO2 formed allow: reaction goes completely to the right (b) (i) C + O2 → CO2;; [2] allow: 1 mark for O2 as reactant / C + 2O → CO2 (ii) limited; air; monoxide; poisonous; [4]

allow: oxygen in place of air note: if dioxide put in third position allow 1 mark for harmless in 4th position

(c) calcium chloride; [1] water; [1] (d) (i) idea of measure the (decrease in) mass / weight; [1] idea of measuring time (intervals); [1] (ii) increases / faster; [1] decreases / slower; [1] increases / faster; [1]

note: the answers above must be comparative allow: 1 mark for fast; slow; fast ignore: reference to time taken [Total: 15]




7 (a) (i) any 4 of: [4] (at 20 °C / at the start) particles are close together / touching / arranged regularly

(at 20 °C / at the start) particles are vibrating / not moving as temperature rises / then particles vibrate more / gain energy at 114 °C / then particles begin to move

forces between particles weaken / molecules start to break away (from each other) at 114 °C / then particles become more randomly arranged / slide over each other

when liquid / above 114 °C / then particles slide over each other/ move when liquid / above 114 °C then particles are randomly arranged ignore: particles further apart / particles (move) faster (ii) 254; [1] (b) (i) ionic; [1] (ii) KI; [1] (c) (1 each) [4] insoluble / does not dissolve; doesn’t conduct; soluble / dissolves; doesn’t conduct; ignore: low / high / not very well (d) + electrode: iodine / I2 / I; [1] – electrode: potassium / K; [1] allow: 1 mark if correct electrode products reversed ignore: iodide [Total: 13]




0620 CHEMISTRY








1 (a) (i) Ar / argon; [1] allow: Ne / neon (ii) S / sulphur; [1] (iii) I / I2 / iodine; [1] allow: P / phosphorus (iv) N / N2 / nitrogen; [1] (v) He / Ne / Ar / helium / neon / argon; [1] (vi) H / H2 / hydrogen; [1] (b) (i) H2 + Cl2 → 2HCl;; [2] if 2 marks not scored: Cl2 on left / H2 + 2Cl → 2HCl (1 mark) (ii) correct dots and cross diagram for Cl2;; [2] allow: 1 pair of shared electrons between 2 (Cl) atoms for 1 mark is 2 marks not scored [Total: 10]

2 (a) (i) ring around –COOH group; [1] (ii) C2H4O2; [1] (atoms can be in any order) ignore: CH3COOH / CH2O (b) neutralisation / acid-base; [1] allow: acid-alkali reaction ignore: exothermic / endothermic (c) dissolves (in water / liquid); [1] ignore: mixes / solute reject: reacts with water (d) pH3; [1] (e) carbon dioxide; water; [2] allow: correct formulae apply: listing (f) Na2CO3; [1] allow: CO3Na2

[Total: 8]




3 (a) solvent line shown below the spot and above the bottom of the paper; [1] (b) (i) chromatography; [1] (ii) 4 spots shown above position of original spot; [1] allow: one spot drawn in on base line spots vertically above the position of the original spot; [1] solvent front as horizontal line above all the spots; [1] allow: solvent front near the top of the paper as horizontal line if no spots drawn allow: top spot on solvent front (c) unsaturated and because it has a (C=C) double bond; [1] [Total: 6] 4 (a) (i) H [1] │ H – C – H │ H (ii) gas which causes global warming / increases temperature of atmosphere; [1] allow: it causes the atmosphere to heat up / causes Earth’s temperature to increase /

traps heat in (iii) from digestion of cows / sheep etc. / marshes / rice paddy fields / bacteria; [1] allow: (animal or bacterial or plant) decay / from animals / from petroleum deposits

underground / from natural gas ignore: from decomposition (iv) 800 (g); [1] (b) (i) has a double headed arrow / has � sign; [1] allow: arrows go both ways / has the reversible symbol allow: can change reaction (conditions) to go from one side or another (ii) reaction which goes backwards as well as forwards / goes both ways; [1] allow: goes backwards as well ignore: goes backwards unqualified / a reaction that can be undone / A reaction that can

be reversed (iii) car exhausts / car engines / product of incomplete combustion of fuels / any named

heating appliance burning carbon-containing fuels / zinc extraction / iron extraction; [1] ignore: fuels (unqualified) / cars (unqualified) (iv) acidic and because oxides of non-metals are acidic / carbon is a non-metal [1] [Total: 8]




5 (a) (i) steam / water; [1] (ii) high temperature / heat / stated temperature 200 °C or above; [1] catalyst; [1] ignore: names of catalysts ignore: pressure (b) (i) glucose (on left); [1] allow: sugar / carbohydrates ignore: starch ignore: formulae carbon dioxide (on right); [1] ignore: formulae (ii) catalyst / description of catalyst; [1] biological / protein / from living things; [1] note: second mark is dependent on the first being correct (c) (i) increase up to 40 °C then decreases; [3] if full marks not scored: increases then decreases / best at 40 ° and slower when cold and very hot = 2 marks maximum at 40 °C / decreases above 40 °C / maximum at 40 ° = 1 mark (ii) any two of: [2] amount of yeast / catalyst / enzyme amount (or concentration) of glucose / sugar ignore: amount of food available amount (or volume) of water / amount (or volume) of solution allow: temperature (during each experiment) ignore: room temperature allow: pH ignore: particle size of sugar ignore: time / size of container (d) (i) points correctly plotted;; [2] (–1 per error / omission) single gently curved line between the points and not extrapolated to 0 [1] (ii) line drawn in part (i) correctly extrapolated with correct value from the extrapolation [1] (value if part (i) correct is 138 (°C)) [Total: 16]




6 (a) (i) petrol (in a few countries) / paints / (old) water pipes; [1] allow: zinc refining / cars / fuels in cars / car exhausts / car engines (ii) poisonous / damage to nerves / brain / learning difficulties; [1] (b) (i) lead(II) oxide + carbon → lead + carbon monoxide; [1] allow: lead oxide on left ignore: carbon oxide / symbol equation reject: wrong oxidation numbers (ii) it loses oxygen / the lead decreases in oxidation number / the lead gains electrons; [1] ignore: carbon is oxidised / lead oxide goes to lead (iii) it needs heat / absorbs heat; [1] allow: absorbs energy / products have more energy than reactants (c) filter funnel + filter paper (in drawings or words); [1] lead iodide shown on filter paper; [1] (d) 82 protons + 82 electrons; [1] 122 neutrons; [1] [Total: 9] 7 (a) silver rod; [1] (b) silver rod: gets smaller / gets thinner / loses mass; [1] allow: corrodes iron spoon: gets coated with silver / increases in mass / gets thicker; [1] allow: gets bigger (c) to prevent corrosion / to make them look nicer (or shiny) / to make (the surface) harder / to

make (the surface) more resistant to chemicals; [1] allow: to prevent rusting / to prevent reactions / to reduce reactivity / to make more durable ignore: protective layer (d) silver atoms lose electrons / 3rd box down ticked; [1] (e) add nitric acid to the solution; [1] allow: acidify the solution reject: add hydrochloric acid / sulfuric acid / phosphoric acid (on addition of silver nitrate) precipitate formed; [1] white (precipitate); [1] note: second and third marks are independent of the fist mark




(f) any 2 of: [2] conducts heat / conducts electricity / malleable / can be beaten into different shapes / can be bent (without breaking) ductile / can be drawn into wires high density / dense sonorous / rings when hit allow: high density ignore: solid ignore: shiny / high melting point / high boiling point / hard / strong [Total: 10] 8 (a) (i) A / at the top; [1] (ii) C; [1] (iii) D; [1] allow: E (b) any 5 of: [5] haematite / other named ore of iron limestone / calcium carbonate coke / carbon / coal (coke) burns in air / oxygen carbon monoxide formed carbon monoxide (or carbon) converts the iron ore (or iron oxide) (this is a) reduction reaction iron oxide / haematite reacts with carbon monoxide to form iron and carbon dioxide limestone forms calcium oxide (on heating) calcium oxide reacts with impurities in ore (to form a) slag / calcium silicate ignore: air note: to gain the marks, the answers must be in the correct context. marks can also be scored from word equations or symbol equations (which do not have to be

correctly balanced) carbon + oxygen → carbon monoxide = 3 carbon dioxide + carbon → carbon monoxide = 2 calcium carbonate → calcium oxide + carbon dioxide = 2 calcium oxide + silicon dioxide → calcium silicate / slag = 2 iron oxide + carbon monoxide → iron + carbon dioxide = 2




(c) (i) iron chloride; [1] ignore: oxidation numbers hydrogen; [1] apply: listing (ii) sodium hydroxide; [1] (grey)-green precipitate; [1] note: second mark is dependent on the correct reagent (d) steel made by blowing oxygen through molten iron / last box ticked; [1] [Total: 13]




0620 CHEMISTRY








1 (a) diffusion or fractional distillation; (b) fractional distillation; (c) simple distillation; (d) crystallisation; (e) filtration;

(f) chromatography;

[Total: 6] 2 (a) (i) become darker; [1] (ii) increase; [1] (iii) black / dark grey; [1] not: brown solid; [1] (b) (i) same Z / same number of protons; [1] accept: atoms of the same element different number of neutrons / different nucleon number / different mass

number; [1] (ii) 53 protons and 53 electrons; [1] 78

neutrons; [1] (iii) xenon; [1] (c) BrF3 / F3Br; [1] BrF5 / F5Br; [1]

[Total: 11]




3 (a) (i) any three from: particles have more energy; move faster; collide more frequently; more successful collisions; [3] accept: atoms or molecules for particles not: electrons not: vibrate more (ii) reaction faster with temperature increase; [1] enzymes denatured / destroyed; not: killed [1] (b) (i) bigger initial gradient; [1] same final volume of nitrogen; [1] (ii) decrease / slows down; [1] (iii) concentration of organic compound decreases; [2] compound used up = [1] or: fewer particles; collision rate decreases; (c) (i) carbon monoxide-incomplete combustion; [1] carbon - containing fuel / fossil fuel / petrol; [1] oxides of nitrogen - oxygen and nitrogen react; [1] at high temperature / in engine; [1] not: in exhaust (ii) carbon monoxide to carbon dioxide; [1] oxides of nitrogen to nitrogen; [1] correct balanced equation; [1] [Total: 17]




4 (a) giant covalent; [1] or: polymer made from monomers; (b) (i) any three from: high mp / bp; hard; brittle; insoluble (in water); poor conductor of electricity / heat; [3] (ii) carbon / diamond / silicon / boron; [1] not: graphite (c) (i) sodium hydroxide / any named alkali / reactive metal; [1] (ii) named acid; [1] zirconium oxide; [1] [Total: 8] 5 (a) (i) rate of reaction; [1] influenced by light / only happens in light; [1] or: turns light into chemical energy = [2] accept: light is catalyst = [1] (ii) reduction of silver halides; [1] they are reduced to silver / 2AgCl → 2Ag + Cl2; [1] appropriate importance given; [1] or: photosynthesis; correct comment about chemistry carbon dioxide to carbohydrates / carbon

dioxide to oxygen; anything sensible e.g. its role in the food chain or decrease greenhouse

effect or oxygen for respiration; or: chlorination; making chloroalkanes; appropriate importance given; (b) (i) pressure would move position of equilibrium to right / increase yield of COCl2; [1] increase pressure favours side with less (gas) molecules / smaller volume; [1] (ii) increase temperature favours endothermic reaction; [1] so less products / reduce yield; [1] (iii) keeps rate high / increase rate at lower temperatures; [1]




(c) each chlorine 1 bp and 3 nbps; [1] 4 e between carbon atom and oxygen atom; [1] 2 nbps on oxygen atom; [1] [Total: 13] 6 (a) (i) amino acid / peptides; [1] salt / carboxylate or soap / fatty acid or glycerine / alcohol; [1] sugars or glucose; [1] accept: named sugar (ii) polyester; [1] allow: named polyester polyamide; [1] allow: nylon (b) one correct amide linkage; [1] second amide linkage correctly orientated – NHCO – followed by – NHCO –; [1] note: monomers are amino acids not diamines or dicarboxylic acid (c) bromine / bromine water / aqueous bromine; [1] unsaturated - brown / orange to colourless not: clear [1] saturated - stays brown / orange [1] or: alkaline potassium manganate(VII); from purple / pink to green / brown; stays purple; or: acidic potassium manganate(VII) from purple / pink to colourless; not: clear stays purple; [Total: 10] 7 (a) (i) melting point is below 25°C; [1] boiling point above 25°C; [1] accept: argument based on actual values note: 25°C is between mp and bp = [2] (ii) strontium loses 2e; [1] sulfur gains 2e; [1] (iii) hydrogen chloride / hydrochloric acid; [1] accept: sulfurous acid or sulfur dioxide (iv) molten strontium chloride has ions / ionic compound; [1] which can move; [1] sulfur chloride has no ions / only molecules / molecular / covalent; [1]




(b) (i) strontium carbonate does not dissolve / no effervescence; [1] note: not just reaction is complete (ii) to remove excess / unreacted / undissolved strontium carbonate; [1] (iii) water of crystallisation needed / 6H2O in crystals / would get anhydrous salt /

would not get hydrated salt / crystals dehydrate; [1] not: just to obtain crystals (c) number of moles of HCl used = 0.05 × 2 = 0.1 [1]

number of moles of SrCl2.6 H2O which could be formed. = 0.05 [1] mass of one mole of SrCl2.6H2O is 267 g

theoretical yield of SrCl2.6H2O = 0.05 × 267 = 13.35 g [1] percentage yield = 6.4 / 13.35 × 100 = 47.9% [1] accept: 48% allow: ecf [Total: 15]




0620 CHEMISTRY








1 (a) (i) Sb; (ii) Xe / B;

(iii) Sr / Te / A / D;

(iv) Sn and I / E and F; (v) Sr / A; [5] (b) any two from: physical niobium is harder; stronger; higher mp/bp; higher density [2] note: there has to be a comparison any two from: chemical niobium is less reactive; forms coloured compounds; forms complex ions; its

compounds have catalytic properties; has more than one oxidation state; has more than one valency electron; [2]

note: the response has to refer to or compare properties of both elements

[Total: 9] 2 (a) liquid; [1] (b) (l) and (s); [1] reversible sign; [1] accept: X in equation ignore: any compounds just look for state symbols must be the same compound on both sides of equation (c) boiling / condensation; [1] accept: evaporation or vaporisation (d) (in region BC) solid melts / liquid boils (in region DE); [1] at one / fixed / sharp / single / specific temperature; [1] [Total: 6] 3 (a) (i) correct structure of an isomer e.g. 2-chloropropane; [1] (ii) chlorine; [1] light / heat / lead tetraethyl; [1]




(iii) could produce 2-chloropropane; [1] could produce HCl; [1] or could produce dichloropropanes = [2] (b) (i) add silver nitrate / lead nitrate; [1] yellow precipitate; [1] note: do not insist on presence of dilute nitric acid

(ii) propanol / propan-1-ol; [1]

(c) (i) for A; reaction slower; decreased collision rate; less bromobutane present / concentration of bromobutane less / less reacting

particles; [2] any two accept: reverse arguments for B

(ii) halogens Cl > Br > I reactivity / reactivity decreases down group; [1]

organic halides I > Br > Cl / reactivity increases down group; [1] opposite without explanation = [1] (iii) any three from: less energy; particles move slower; less collisions / fewer particles have energy to react / fewer successful collisions; slower rate; [3] [Total: 15] 4 (a) C + O2 → CO2 [1] (b) (i) CO2 already formed (from C burning or from CaCO3); [1] then carbon reacts with carbon dioxide; [1] or C + CO2 → 2CO = [2] If equation not balanced = [1] (ii) Fe2O3 + 3CO → 2Fe + 3CO2 [2] not balanced = [1] not: reduction by carbon (c) to remove / neutralise silica / silicon dioxide / silicon(IV) oxide / sand; [1] reacts with limestone to form slag / calcium silicate; [1] CaCO3 + SiO2 → CaSiO3 + CO2 [1] or CaO + SiO2 →CaSiO3

or CaCO3 → CaO + CO2




(d) (i) galvanising / galvanisation / sacrificial protection; [1] (ii) sacrificial protection / zinc is sacrificed; zinc corrodes rather than iron; zinc is oxidised in preference to iron; zinc reacts with oxygen and / water in preference to iron; zinc more reactive / electropositive than iron; zinc loses electrons more readily than iron; electrons move on to iron any three [3]

[Total: 12]

5 (a) any two from: bleaching (wood pulp / silk / straw); manufacture of sulfuric acid / SO3 / in Contact process; fumigating / sterilising; refrigerant; making dyes; making wine; insecticide;

fungicide; [2] (b) burn / heat / react sulfur; [1] in air / oxygen; [1] or burn / heat / roast zinc sulfide or lead sulfide; in air / oxygen; (c) from purple / pink; not: red [1] to colourless; not clear [1]

(d) number of moles of Na2SO3 = 3.15/126 = 0.025 [1] number of moles of SO2 formed = 0.025 [1] volume of SO2 = 0.025 x 24 = 0.6 dm3/litres or 600 cm3 [1] allow: ecf for 1.6 g of SO2 [1] only If used 22.4 max [2] note: need correct units for last mark [Total: 9]




6 (a) (i) correct arrow from negative terminal of battery or from anode; [1] (ii) from battery / power supply / cell; [1] from negative electrode of battery to external circuit; [1] or from anode; from iodide ion losing electron or oxidation of anion; (iii) ions cannot move in solid / ions can move in liquid; [1] (b) copper; [1] (changes to) sulfuric acid; [1]

hydrogen; [1] (changes to) potassium hydroxide; [1]

(c) (i) 2H+ + 2e � H2 [2] not balanced = [1] (ii) 4OH- � O2 + 2H2O + 4e [1] (iii) water used up; [1] (d) it is a cell; [1] hydrogen reacts with oxygen; [1] this reaction produces energy / is exothermic / produces flow of electrons /

changes chemical energy to electrical energy; [1]

[Total: 15] 7 (a) (i) CnH2n+1OH [1] (ii) 116-17 = 99, 2n+1 = 99, n = 7 for any evidence of working out [1] C7H15OH [1] (iii) 4bps around C; [1] 1 bp on each hydrogen; [1] 2bps and 2nbps on oxygen; [1] (b) (i) increases yield / moves equilibrium to RHS / favours forward reaction; [1] high pressure favours side with smaller number of (gas) molecules; [1]

(ii) any two from: higher temperature / catalyst causes faster reaction; comment about compromise conditions to give best rate and yield;

at 250oC (lower temp) higher yield / forward reaction favoured; at 350oC (higher temp) lower yield / back reaction favoured; [3]




(c) (i) methanoic acid; [1] correct SF showing all bonds; [1] accept: -OH (ii) methyl methanoate; [1] [Total: 14]




0620 CHEMISTRY








1 (a) Ca / calcium; [1] (b) Kr / krypton; [1] (c) Ge / germanium; [1] (d) Ni / nickel or Cr / chromium; [1] (e) Br / bromine / Br2; [1] (f) Se / selenium; [1] (g) Cu / copper; [1] (h) Br / bromine / Br2; [1] [Total: 8] 2 (a) (i) manufacture of plastics / (solvents for) dry cleaning / metal degreasing / textiles

/ agrochemicals / pharmaceuticals / insecticides / dyestuffs / household cleaning products / bleach / water treatment / swimming pools / kill bacteria or germs or microorganisms or pathogens / sterilisation / disinfectants; [1]

(ii) electric light bulbs / fluorescent tubes / (inert gas shield for) arc welding /

production of titanium / inert atmosphere / car headlights / food packaging; [1] (iii) (manufacture of) polyethene / polyvinyl chloride (PVC) / making polymers / (to

prepare) epoxyethane (which is used in the manufacture of detergents / (to make) ethylene glycol (which is used to prepare Terylene) / (to make) anti-freeze / or making ethanol (accept making alcohol) / ripening fruits; [1]

(iv) (making) steel / (oxy-acetylene) welding / cutting of metals / medical or diving or

(oxygen tanks in) hospitals / astronauts / (deep sea) diving / fire fighters; [1]

(b) liquid air; [1] fractional distillation; [1]

[Total: 6]




3 (a) explanation of evaporation e.g. particles (or molecules) with a lot of energy leave the liquid / bromine particles break free from each other / forces or bonds between bromine molecules broken / molecules (in liquid) have weak forces holding them together / weak intermolecular forces / Van der Waals forces between molecules (don’t have to be stated as weak) / (weak intermolecular forces alone scores this mark);

allow: particles (or molecules) of bromine escape from liquid [1] diffusion / diffuse / movement of particles; [1]

explanation of diffusion involving qualified movement of molecules / particles i.e. random movement of molecules / particles move in all directions; [1]

(b) air more dense / heavier / higher Mr than hydrogen; [1] hydrogen diffuses faster (than air diffuses out); [1] accept: diffusion in is faster than out (without naming gases) pressure inside pot is greater (than outside); [1] air less dense / lighter / lower Mr than carbon dioxide; [1] air diffuses / moves faster (than carbon dioxide); [1] accept: diffusion out is faster than in (without naming gases) pressure inside pot less (than outside); [1] ORA in both parts

[Total: 9] 4 (a) (i) zinc mixed with an element(s) or metal(s) or non-metal; [1] (ii) galvanising / baths / coating steel (i.e. description of galvanising) / roofing /

sacrificial protection / protection from rusting / electroplating / zinc plating / batteries; [1]

(iii) (lattice) positive ions / cations / metal ions / sea of electrons / delocalised or free

or mobile or moving electrons; [1] attraction between positive ions and electrons; [1] the layers (of ions) or particles can slide or slip or shift past each other; [1] (iv) different atom / ion / particle of different size; [1] prevents (layers / atoms / ions / particles / molecules) moving / slipping /

sliding / shifting; [1] (b) (i) heat with carbon or coke or carbon monoxide; [1] (ii) ZnO + H2SO4 � ZnSO4 + H2O [2] [1] for correct reactants [1]for correct products




(iii) zinc (not: ions) more reactive than silver and lead; [1] zinc displaces both metals / silver and lead produced / ions become atoms / zinc

reduces silver ions and lead ions; [1] (silver and lead) can be removed by filtering / centrifugation / decanting; [1]

an ionic equation; i.e. Zn + 2 Ag+ � Zn2+ + 2Ag or Zn + Pb2+ � Zn2+ + Pb [1] allow: any two correct half equations

(iv) cathode labelled carbon / zinc / platinum; [1] zinc deposited at cathode; [1] oxygen formed (at anode); [1] (electrolyte becomes) sulfuric acid / remaining solution contains H+ and SO4

2-; [1] [Total: 18] 5 (a) (i) add bromine water / bromine / aqueous bromine; [1] colourless; [1]

or add potassium manganate(VII) / permanganate; (ignore acid or alkali) [1] colourless; [1] (ii) add metal / carbonate / insoluble base / strong alkali allow: ammonia with an

indicator / use pH meter; [1] COND: on reagent

metal - hydrogen given off / metal dissolves / effervescence / gas given off / burning splint pops; carbonate - carbon dioxide given off / effervescence / gas given off / limewater milky; insoluble base - solution formed / dissolves; alkali - use of indicator to show neutralisation / temperature increase; pH meter - gives pH less than 7 [1]

(b) ethyl propenoate; [1] correct SF all bonds shown;; [2] allow: [1] for correct displayed ester linkage




(c) (i) number of atoms of each element; [1] in one molecule; [1] (ii) 2; [1] (iii) C=C [1]

(iv) HOOC(CH3)C=C(CH3)COOH [Total: 12]

6 (a) (i) Zn + 2HCl � ZnCl2 + H2 [2] not balanced = [1] (ii) 3 bps and 1 nbp around As; [1] 1 bp each hydrogen atom; [1] (b) (i) (97.4 / 75 =) 1.3 and (2.6 / 1 = ) 2.6; [1] empirical formula AsH2; [1] note: correct formula with no working = [1] (ii) As2H4; [1] (iii) H2As–AsH2 / AsH2–AsH2; [1] (c) (i) amide / peptide; [1] (ii) named strong acid / alkali; [1] allow: HCl / enzymes (iii) amino acid; [1] allow: peptides (d) (i) Cu and As have more than one oxidation state / valency; [1] (ii) 3Cu2+ + 2AsO4

3- � Cu3(AsO4)2 [2] either side correct = [1] [Total: 14]




7 (a) (making) fertilisers / nitric acid / nylon / refrigeration / explosives / cleaning products; [1] (b) alkane / named alkane; [1] water / steam; [1] heat / catalyst; [1] or electrolysis; [1] suggest suitable electrolyte; (allow: water) [1] hydrogen at cathode; [1] or cracking; [1] alkane / named alkane; [1] heat or catalyst [1] (c) any five from: faster; (rate) [1]

more collisions / molecules closer together / more particles per unit volume; [1] (collisions) more frequent / more often / more chance / more effective or successful collisions / more collisions with Ea / increase rate of collisions; [1] higher yield / moves (equilibrium) to RHS / more ammonia / to side of products / high pressure favours the reaction with less moles; [1] less moles / molecules / volume on RHS ORA (can be implied in previous comments) [1] high pressure means lower temperature can be used to achieve comparable rate (thus saving energy); [1]

7 (d) (i) endothermic takes in / absorbs / uses / needs / gains energy / heat and

exothermic gives out / loses energy / heat; [1] (ii) 2328 (ignore + or – ) / 6 × 388 (not evaluated); [1] 944 + 1308 / 2252 and endothermic and exothermic in table; [1] 2328>2252 or (–) 76 kJ; [1] or energy of products / RHS > reactants / LHS or energy needed to break bonds < energy given out on formation of bonds. [Total: 13]




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1 (e) Table of results for Experiments all initial temperature boxes completed correctly as instructed (1) all final temperature boxes completed correctly not more than 20 °C below original (1) all average temperatures completed correctly (1) times completed in seconds (1) ignore: dps descending in order (comparable to supervisor) (1) [5] (f) points plotted correctly (4) smooth line graph (1) [5] (g) average temperature 72 °C (1) value from graph (1)

extrapolation shown on grid (1) [3]

(h) as an indicator/check presence of iodine owtte (1) [1] (i) (i) experiment 5/when temperature is 70 (1) [1] (ii) highest temperature (1)

particles have more energy/more collisions (1) [2] (j) time longer/more/increase (1)

speed slower/decrease (1) [2]

(k) more accurate (1) [1]

2 (a) pH 5–7 (1) ignore colours [1]

(b) (i) white (1) precipitate (1) dissolves owtte (1) [3] (ii) white (1) precipitate (1) dissolves owttte (1) [3] (c) no reaction/no change/no precipitate/no observation (1) [1] (d) white (1) precipitate (1) [2]



3

(e) litmus turns red (1) then bleached/white (1) [2] (f) bubbles/fizz etc. (1)

glowing splint (1) glows brighter/relights (1) [3]

(g) zinc (1) sulfate (1) [2] (h) oxygen (1) [1] (i) transition metal present (1) catalyst (1) manganese/copper (1) oxide (1) max 2 [2] [Total: 40]




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1 (e) Table of results for Experiments all initial temperature boxes completed correctly as instructed (1) all final temperature boxes completed correctly not more than 20 °C below original (1) all average temperatures completed correctly (1) times completed in seconds (1) ignore: dps descending in order (comparable to supervisor) (1) [5] (f) points plotted correctly (4) smooth line graph (1) [5] (g) average temperature 72 °C (1) value from graph (1)

extrapolation shown on grid (1) [3]

(h) as an indicator/check presence of iodine owtte (1) [1] (i) (i) experiment 5/when temperature is 70 (1) [1] (ii) highest temperature (1)

particles have more energy/more collisions (1) [2] (j) time longer/more/increase (1)

speed slower/decrease (1) [2]

(k) more accurate (1) [1]

2 (a) pH 5–7 (1) ignore colours [1]

(b) (i) white (1) precipitate (1) dissolves owtte (1) [3] (ii) white (1) precipitate (1) dissolves owttte (1) [3] (c) no reaction/no change/no precipitate/no observation (1) [1] (d) white (1) precipitate (1) [2]



3

(e) litmus turns red (1) then bleached/white (1) [2] (f) bubbles/fizz etc. (1)

glowing splint (1) glows brighter/relights (1) [3]

(g) zinc (1) sulfate (1) [2] (h) oxygen (1) [1] (i) transition metal present (1) catalyst (1) manganese/copper (1) oxide (1) max 2 [2] [Total: 40]




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1 (a) table of results for experiment 1 initial temperature box completed correctly (1) other temperature boxes correctly completed (1) comparable to supervisors (1) [3] (b) table of results for experiment 2 initial temperature box completed correctly (1) other temperature boxes correctly completed (1) comparable to supervisors (1) [3] (c) all points correctly plotted (3), –1 for any incorrect best fit smooth line graphs (2) labels (1) [6] (d) value from graph (1) shown clearly (1) [2] (e) exothermic (1) [1] (f) (i) experiment identified from results obtained (1) [1] (ii) acid H is more concentrated/stronger (1) [1] (g) room/initial temperature from table (1) reaction finished owtte (1) [2] 2 (a) green [1] (b) green (1) (precipitate) turns brown/rusty at top (1) [2] (c) effervescence/fizz/bubbles (1) glowing splint (1) glows brighter/relights/burns (1) [3] (d) green precipitate (1) [1] (e) no reaction/change (1) [1] (f) white (1) precipitate (1) [2] (g) blue (1) [1]




(h) green/white/blue (1) according to supervisor’s precipitate (1) turns green (1) [3]

(i) fizz/bubbles/ammonia (1) litmus/indicator paper blue/purple (1) [2]

(j) iron(1) (II) (1) sulfate (1) [3] (k) transition metal (1) nitrate (1) [2] [Total: 40]




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1 (a) arrow under copper oxide (1) [1] (b) black (1) to brown/red (1) [2] (c) diagram of tube entering test-tube or similar in beaker of cold water/ice/Liebig [2] condenser (1) labelled water/ice/condenser (1) (d) extinguished/goes out (1) not: no effect/no reaction [1] 2 (a) carbon/graphite/platinum (1) [1]

(b) negative/cathode (1) [1]

(c) bubbles/fizz/ colour of solution pales (1) not: gas given off ignore wrong gas [1]

(d) (i) with distilled/pure water (1) accept: organic solvents [1]

(ii) use of hairdryer/oven (1) allow: heat/heater [1]

(e) increase in masses completed correctly (1) [1]

0.75 1.00 1.15 1.15 1.15 accept 1 for 1.00

(f) points plotted correctly (2), –1 any incorrect [3] two straight lines through points (1)

(g) reaction finished/all copper deposited owtte/all copper sulfate used up (1) [1] 3 (a) (i) silver/grey (1) not: shiny [1] (ii) white (1) [1] (b) oxygen (1) [1] (c) to let air/oxygen enter or make sure all magnesium reacted owtte (1) [1]




(d) error in weighing (1) [2] loss of magnesium oxide (1) some magnesium unreacted (1) max 2 4 (a) Table of results for Experiments [5] all initial temperature boxes completed correctly (2)

25 41 47 62 72 all final temperature boxes completed correctly (2)

23 27 39 42 48 average temperatures completed correctly (1)

24 34 43 52 60 (b) points plotted correctly (4) [5] smooth line graph (1) (c) value from graph at 72

°C (1) ≈ 30–35 s [2]

extrapolation shown on grid (1)

(d) as an indicator owtte/check iodine present (1) [1] (e) (i) experiment 5 (1) [1] (ii) highest temperature (1) [2]

particles have more energy/more collisions/move faster (1) (f) time longer/more/increase (1) [2]

speed slower/decrease (1)

(g) more accurate (1) [1]




5 (a) (i) white (1) precipitate (1) dissolves (1) [3] (ii) white precipitate (1) dissolves (1) [2] (b) no reaction/change (1) [1] (c) white (1) precipitate (1) [2] (g) chlorine (1) not: chloride [1] (h) oxygen (1) [1] (i) transition metal present (1) catalyst (1) allow: copper oxide for one mark [2] manganese (1) oxide (1) max 2 6 any seven from: equal weight/mass of limestone and marble (1) [7] crush (1) add excess owtte (1) hydrochloric acid (1) stir (1) filter mixture (1) dry (1) reweigh (1) conclusion (1) [Total: 60]




0620 CHEMISTRY

0620/62 Paper 6 (Alternative to practical), maximum raw mark 60







1 (a) flask (1) measuring/graduated cylinder (1) [2] (b) (i) does not react/unreactive/not reactive enough/below hydrogen in the reactivity series (1) [1] (ii) magnesium/zinc/iron/aluminium (1) [1]

(c) diagram of (gas) syringe (1) syringe labelled (1) [2]

(d) lighted splint/flame test (1) pops (1) [2]

2 (a) straight line drawn with a ruler missing point at concentration 0.15 (1) through origin (1) [2]

(b) 0.56/0.57/0.58 (1) extrapolation shown (1) [2]

(c) line to right hand side of original and goes through origin (1) [1] (d) (i) catalyst/to speed up the reaction (1) [1] (ii) slower/owtte (1)

less surface area (1) [2] 3 (a) spatula (1) not: spoon [1] (b) nitric/HNO3 (1) [1] (c) (i) toxic/poisonous/harmful gas given off or named toxic gas (1) [1]

(ii) idea of ensuring constant mass (1) reaction complete (1) [2]

(d) (i) spillage (1) inaccurate weighing (1) loss by spitting (1) reaction not complete/owtte (1) some solid left in beaker (1) [2]




4 (a) Table of results for Experiment 1 temperature boxes completed correctly (3), –1 any incorrect 23 27 31 34 36 35 34 33 32 [3] (b) Table of results for Experiment 2 temperature boxes completed correctly (3), –1 for each incorrect 23 28 32 35 37 38 39 38 36 [3] (c) all points correctly plotted ±1/2 small space(3) –1 for any incorrect best fit smooth line graphs (2) labels (1) [6] (d) value from graph ,29–30 °C (1) shown clearly (1) [2] (e) exothermic (1) [1] (f) (i) experiment 2/acid H (1) [1] (ii) acid (H) is more concentrated/stronger (1) [1] (g) room/initial temperature from table/23

°C (1) reaction finished/owtte (1) [2]

5 (a) green (1) [1]

(b) green (1) precipitate (1) [2] (c) green precipitate (1) [1] (d) no reaction/no precipitate/no change/no observation/nothing (1) [1]

(e) white (1) precipitate (1) [2]

(i) ammonia (1) [1]

(j) transition metal/cobalt (1) ignore copper nitrate (1) [2




6 (a) test (1) e.g. add named indicator/marble chip/magnesium result (1) e.g. ethanoic acid changes colour of indicator/ethanoic acid effervesces [2] allow: lighted splint (1) ethanol burns (1) (b) any 6 from: weigh coal/equal masses/equal amounts (1) crush (1) heat (1) in a fume cupboard (1) pass through potassium manganate (1) time to colourless (1) repeat with other coal (1) compare/conclusion (1) [6] [Total: 60]




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1 (a) (i) set B (1) accept: D or B and D [2]

(ii) arrow positioned anywhere towards liquid (1)

(b) effect bung shoots out/test-tube cracks/shatters/explodes (1) [2] reference to pressure (1)

(c) diagram showing delivery tube into trough with water and collecting vessel (1) [2]

labelled (1) note: gas syringe = 0 2 (a) hydrogen (1) [1] (b) volumes completed correctly [3]

0 18 30 40 43 54 58 60 –1 for each incorrect ignore extra decimal place e.g. 43.00

(c) points plotted correctly (3) [4] smooth curve (1) –1 for each incorrect (d) (i) point at 4 minutes (1) off curve owtte (1) [2]

(ii) 47 – 49 (1) ignore units [2] indication on graph (1)

(e) magnesium powder/higher temperature/more concentrated acid/catalyst used (1) [2]

faster/more surface area/more collisions (1)




3 (a) initial readings [3] 0.0 17.5 8.9

final readings

23.8 40.7 32.3 (2), –1 any incorrect differences

23.8 23.2 23.4 (1) (b) titration 2 and 3/23.2 and 23.4 (1) [2]

average = 23.3 (1) allow: ecf for calculation of average

(c) pipette/burette (1) [1] (d) blue to red/pink (1) [1] (e) (i) half as much acid S/twice as much HCl (1) [1] (ii) y = 2 (1) [1]

4 tests on filtrate

(a) (i) white (1) precipitate (1) with excess does not dissolve/clear (1) [3] (ii) no precipitate/very slight precipitate/no reaction [1] (iii) white (1) precipitate (1) [2]

(c) carbon dioxide/CO2 (1) [1]

(d) lead/silver (1) carbonate (1) [2] 5 (a) Temperature boxes completed correctly (2), –1 for each incorrect [3] 25 31 37 42 48 48 48 Temperature rises calculated correctly (1) 0 6 12 17 23 23 23




(b) all points correctly plotted (3), –1 for any incorrect [5]

smooth straight line graphs drawn with a ruler (1)

labels (1) (c) (i) value from graph (1) 0.50 – 0.52 g allow: 0.5 g ignore units [1]

(ii) value from graph (1) 8.5 – 9.0 °C [1] allow: 9 °C ignore units

(d) 0.8 g (1) [1]

(e) zinc (1) [2]

temperature stays same when increasing amounts added/no more heat given off/no further

reaction (1)

(f) no temperature changes (1) does not react owtte (1) [2] 6 any 7 from: [7] known mass or volume of fats/oil (1)

add organic solvent (1) shake/stir (1) add drops of bromine water (1) until orange colour seen (1) read and record volume/number of drops (1) compare oils (1) conclusion (1) [Total: 60]

Chemistry Markscheme (All in One)

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