C7 til June10

*OCE/16026*

GENERAL CERTIFICATE OF SECONDARY EDUCATION

TWENTY FIRST CENTURY SCIENCE A323/01CHEMISTRY AUnit 3: Ideas in Context plus C7 (Foundation Tier)

F

INSTRUCTIONS TO CANDIDATES

• Write your name clearly in capital letters, your Centre Number and Candidate Number in the boxes above.• Use black ink. Pencil may be used for graphs and diagrams only.• Read each question carefully and make sure that you know what you have to do before starting your answer.• Answer all the questions.• Do not write in the bar codes.• Write your answer to each question in the space provided. Additional paper may be used if necessary but

you must clearly show your Candidate Number, Centre Number and question number(s).

INFORMATION FOR CANDIDATES

• The number of marks is given in brackets [ ] at the end of each question or part question.• The total number of marks for this paper is 55.• Where you see this icon you will be awarded a mark for the quality of written communication in

your answer.

• The Periodic Table is printed on the back page.• This document consists of 12 pages. Any blank pages are indicated.

* A 3 2 3 0 1 *

OCR is an exempt CharityTurn over

© OCR 2010 [D/103/3792]DC (SJF5582/CGW) 16026/4

Candidates answer on the Question PaperA calculator may be used for this paper

OCR Supplied Materials:• Insert (inserted)

Other Materials Required:• Pencil• Ruler (cm/mm)

Friday 28 May 2010Morning

Duration: 60 minutes

2

© OCR 2010

Answer all the questions.

1 This question is based on the article ‘Which nappy is best for the environment?’

(a) Both disposable and reusable ‘terry’ nappies contain cellulose fibres from cotton. Cotton is generally considered to be a renewable material.

(i) Why is cotton considered to be a renewable material?

...........................................................................................................................................

...................................................................................................................................... [1]

(ii) Some people say that although cotton is a renewable material its use is not really sustainable because of the way that we grow it.

What information in the article supports this argument?

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(iii) Some people consider that the use of polyethene and polypropene to make disposable nappies is not sustainable.

Suggest an argument to support this view.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(b) Many parents think that reusable nappies cause less environmental damage than disposable nappies.

Despite this, most parents use disposable nappies.

Suggest a reason why they do this.

...................................................................................................................................................

.............................................................................................................................................. [1]

(c) (i) The article says that a Life Cycle Assessment (LCA) follows the lifetime of a product ‘from cradle to grave’.

Explain what this means.

...........................................................................................................................................

...................................................................................................................................... [1]

3

Turn over© OCR 2010

(ii) In an LCA the environmental impact of a number of stages in the lifetime of a product are considered.

Write down two of these stages that are mentioned in the article.

1 ........................................................................................................................................

2 ................................................................................................................................... [2]

(d) The article says scientists found that the main environmental impacts are different for each type of nappy.

(i) Write down the two main environmental impacts for disposable nappies.

...........................................................................................................................................

...................................................................................................................................... [2]

(ii) Write down the two main environmental impacts for reusable nappies.

...........................................................................................................................................

...................................................................................................................................... [2]

[Total: 13]

4

© OCR 2010

2 (a) The diagram shows the structural formula of the compound ethanol.

CH

H

H

C O H

H

H

(i) To which family of organic compounds does ethanol belong?

...................................................................................................................................... [1]

(ii) What is the molecular formula of ethanol?

...................................................................................................................................... [1]

(b) The table compares some of the properties of ethanol with those of ethane and water.

Complete the table by filling in the blank boxes.

ethane ethanol water

state at 25°C gas liquid

dissolves in water no yes

burns in air yes[3]

(c) A dilute solution of ethanol can be made by fermentation of grape juice using yeast.

(i) What substance in the grape juice is used by yeast to produce ethanol?

...................................................................................................................................... [1]

(ii) Why is it not possible to make a concentrated solution of ethanol by fermentation?

...........................................................................................................................................

...................................................................................................................................... [1]

(iii) Name the method used to separate ethanol from the solution, and explain how it works.

method: .............................................................................................................................

explanation: .......................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [3]

[Total: 10]

5


3 Look at this energy level diagram for the complete combustion of methane in air.

energy level

energydifference

methane + oxygen

carbon dioxide + water

course of reaction

(a) The complete combustion of methane in air is an exothermic reaction.

(i) How does the energy level diagram show that this reaction is exothermic?

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(ii) Write a word equation for the reaction.

...................................................................................................................................... [1]

(b) Complete these sentences to describe the energy change that takes place.

When chemical bonds are broken, energy is ..................................................................... .

When chemical bonds are made, energy is ...................................................................... . [1]

(c) A mixture of methane and oxygen at room temperature does not react.

When a lighted match is applied the mixture burns.

The lighted match supplies the activation energy for the reaction.

Explain what is meant by the term activation energy.

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

[Total: 6]

6

© OCR 2010

4 A scientist employed by the Food Standards Agency uses paper chromatography. He tests samples of water-soluble food dyes to see if they contain a banned compound.

The resulting chromatogram is shown below.

A B C D bannedcompound

dyes

start line

solvent front

(a) Describe how the scientist carries out this chromatography.

One mark is for correct spelling.

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

.......................................................................................................................................... [3+1]

(b) (i) Explain what is meant by the label solvent front, used in the diagram.

...........................................................................................................................................

...................................................................................................................................... [1]

(ii) The scientist used a pencil to mark the start line. Suggest why he did not use a pen.

...........................................................................................................................................

...................................................................................................................................... [1]

7


(c) (i) Which dye, A, B, C or D, contained the banned compound?

answer ........................................................... [1]

(ii) Explain your answer to part (c)(i).

...........................................................................................................................................

...................................................................................................................................... [1]

(iii) State the two measurements the scientist has to make to find the Rf value of the banned compound.

...........................................................................................................................................

...................................................................................................................................... [2]

[Total: 10]

8

© OCR 2010

5 A student uses a titration with nitric acid to find the concentration of a solution of sodium hydroxide.

(a) The student has a stock solution of nitric acid containing 63 g in each dm3.

She uses this to make up 250 cm3 of a standard solution containing 6.3 g in each dm3.

(i) Describe how she makes up this standard solution.

(1 dm3 = 1000 cm3)

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(ii) Finish this statement about the solution she makes by adding the correct units.

The concentration of the solution is 6.3 …………… . [1]

(b) To carry out the titration the student measures out 25.0 cm3 of the sodium hydroxide solution.

To this she adds a few drops of indicator.

She then adds the standard nitric acid solution a little at a time.

(i) Why does she not use a 25 cm3 measuring cylinder to measure out the sodium hydroxide solution?

...................................................................................................................................... [1]

(ii) Suggest what apparatus the student does use to measure out the sodium hydroxide solution.

...................................................................................................................................... [1]

(iii) Explain why she adds an indicator to the sodium hydroxide solution.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

[Total: 7]

9


6 Ammonia is a bulk chemical made by the reaction of nitrogen with hydrogen.

N2 + 3H2 2NH3

The diagram shows a flow chart of the Haber process for the manufacture of ammonia.

hydrogen

nitrogen

85% recycled

15%

reaction vessel

iron catalysthigh pressure

450 °C

air

natural gas and water

ammonia

(a) (i) What is meant by the term bulk chemical.

...........................................................................................................................................

...................................................................................................................................... [1]

(ii) The equation for the formation of ammonia from nitrogen and hydrogen contains the symbol .

Why is this symbol used in the equation?

...........................................................................................................................................

...................................................................................................................................... [1]

(b) Air and natural gas are used to make ammonia.

Suggest how each of these raw materials affects the sustainability of the process.

air: .............................................................................................................................................

...................................................................................................................................................

natural gas: ...............................................................................................................................

.............................................................................................................................................. [4]

(c) The process uses an iron catalyst.

What effect does the catalyst have on the process?

.............................................................................................................................................. [1]

10

© OCR 2010

(d) Ammonia is toxic and corrosive.

It is a gas at room temperature but is transported in road tankers as a liquid under pressure.

Suggest how government safety regulations apply to the transport of ammonia in road tankers.

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

[Total: 9]

END OF QUESTION PAPER

11

© OCR 2010

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12

© OCR 2010

The

Peri

odic

Tab

le o

f th

e El

emen

ts

* T

he l

anth

anoi

ds (

atom

ic n

umbe

rs 5

8-71

) an

d th

e ac

tino

ids

(ato

mic

num

bers

90-

103)

hav

e be

en o

mit

ted.

The

rela

tive

ato

mic

mas

ses

of c

oppe

r an

d ch

lori

ne h

ave

not

been

rou

nded

to

the

near

est

who

le n

umbe

r.

12

34

56

70

Key

1 Hhy

drog

en

1

4 He

heliu

m

2

7 Lilit

hium 3

9 Bebe

rylli

um

4

rela

tive

ato

mic

mas

sat

omic

sym

bol

nam

e

atom

ic (

prot

on)

num

ber

11 Bbo

ron

5

12 Cca

rbon 6

14 Nni

trog

en

7

16 Oox

ygen 8

19 Ffl

uori

ne

9

20 Ne

neon 10

23 Na

sodi

um

11

24 Mg

mag

nesi

um

12

27 Al

alum

iniu

m

13

28 Sisi

licon

14

31 Pph

osph

orus

15

32 Ssu

lfur

16

35.5 Cl

chlo

rine

17

40 Ar

argo

n

18

39 Kpo

tass

ium

19

40 Caca

lciu

m

20

45 Scsc

andi

um

21

48 Titi

tani

um

22

51 Vva

nadi

um

23

52 Crch

rom

ium

24

55 Mn

man

gane

se

25

56 Fe iron 26

59 Co coba

lt

27

59 Ni

nick

el

28

63.5

Cu copp

er

29

65 Zn zinc 30

70 Ga

galli

um

31

73 Ge

germ

aniu

m

32

75 As

arse

nic

33

79 Sese

leni

um

34

80 Brbr

omin

e

35

84 Krkr

ypto

n

36

85 Rbru

bidi

um

37

88 Srst

ront

ium

38

89 Yyt

triu

m

39

91 Zrzi

rcon

ium

40

93 Nb

niob

ium

41

96 Mo

mol

ybde

num

42

[98] Tc

tech

neti

um

43

101

Ruru

then

ium

44

103

Rhrh

odiu

m

45

106

Pdpa

lladi

um

46

108

Ag

silv

er

47

112

Cdca

dmiu

m

48

115

Inin

dium

49

119

Sn tin 50

122

Sban

tim

ony

51

128

Tete

lluri

um

52

127 I

iodi

ne

53

131

Xe xeno

n

54

133

Csca

esiu

m

55

137

Baba

rium

56

139

La*

lant

hanu

m

57

178

Hf

hafn

ium

72

181

Tata

ntal

um

73

184

Wtu

ngst

en

74

186

Rerh

eniu

m

75

190

Os

osm

ium

76

192 Ir

irid

ium

77

195

Ptpl

atin

um

78

197

Au

gold 79

201

Hg

mer

cury

80

204

Tlth

alliu

m

81

207

Pb lead 82

209

Bibi

smut

h

83

[209

]Po

polo

nium

84

[210

]A

tas

tati

ne

85

[222

]Rn rado

n

86

[223

]Fr

fran

cium

87

[226

]Ra

radi

um

88

[227

]A

c*ac

tini

um

89

[261

]Rf

ruth

erfo

rdiu

m

104

[262

]D

bdu

bniu

m

105

[266

]Sg

seab

orgi

um

106

[264

]Bh

bohr

ium

107

[277

]H

sha

ssiu

m

108

[268

]M

tm

eitn

eriu

m

109

[271

]D

sda

rmst

adti

um

110

[272

]Rg

roen

tgen

ium

111

Elem

ents

wit

h at

omic

num

bers

112

-116

hav

e be

en r

epor

ted

but

not

fully

auth

enti

cate

d

Oxford Cambridge and RSA Examinations

GCSE

Chemistry A General Certificate of Secondary Education A323/01

Unit 3: Ideas in Context plus C7

Mark Scheme for June 2010

OCR (Oxford Cambridge and RSA) is a leading UK awarding body, providing a wide range of qualifications to meet the needs of pupils of all ages and abilities. OCR qualifications include AS/A Levels, Diplomas, GCSEs, OCR Nationals, Functional Skills, Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT, business, languages, teaching/training, administration and secretarial skills. It is also responsible for developing new specifications to meet national requirements and the needs of students and teachers. OCR is a not-for-profit organisation; any surplus made is invested back into the establishment to help towards the development of qualifications and support which keep pace with the changing needs of today’s society. 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 marks were awarded by Examiners. It does not indicate the details of the discussions which took place at an Examiners’ meeting before marking commenced. 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 should be read in conjunction with the published question papers and the Report on the Examination. OCR will not enter into any discussion or correspondence in connection with this mark scheme. © OCR 2010 Any enquiries about publications should be addressed to: OCR Publications PO Box 5050 Annesley NOTTINGHAM NG15 0DL Telephone: 0870 770 6622 Facsimile: 01223 552610 E-mail: [email protected]

A323/01 Mark Scheme June 2010

Guidance for Examiners

Additional Guidance within any mark scheme takes precedence over the following guidance. 1. Mark strictly to the mark scheme.

2. Make no deductions for wrong work after an acceptable answer unless the mark scheme says otherwise.

3. Accept any clear, unambiguous response which is correct, e.g. mis-spellings if phonetically correct (but check additional guidance).

4. Abbreviations, annotations and conventions used in the detailed mark scheme:

/ = alternative and acceptable answers for the same marking point (1) = separates marking points not/reject = answers which are not worthy of credit ignore = statements which are irrelevant - applies to neutral answers allow/accept = answers that can be accepted (words) = words which are not essential to gain credit words = underlined words must be present in answer to score a mark ecf = error carried forward AW/owtte = alternative wording ORA = or reverse argument E.g. mark scheme shows ‘work done in lifting / (change in) gravitational potential energy’ (1) work done = 0 marks work done lifting = 1 mark change in potential energy = 0 marks gravitational potential energy = 1 mark

5. Annotations: The following annotations are available on SCORIS.

= correct response = incorrect response bod = benefit of the doubt nbod = benefit of the doubt not given ECF = error carried forward ^ = information omitted I = ignore R = reject

6. If a candidate alters his/her response, examiners should accept the alteration.

7. Crossed out answers should be considered only if no other response has been made. When marking crossed out responses, accept correct answers which are clear and unambiguous.

1


2

E.g. For a one mark question, where ticks in boxes 3 and 4 are required for the mark:

Put ticks () in the two correct boxes.

This would be worth 0 marks.


This would be worth one mark.



8. The list principle: If a list of responses greater than the number requested is given, work through the list from the beginning. Award one mark for each correct response, ignore any neutral response, and deduct one mark for any incorrect response, e.g. one which has an error of science. If the number of incorrect responses is equal to or greater than the number of correct responses, no marks are awarded. A neutral response is correct but irrelevant to the question.

9. Marking method for tick boxes:

Always check the additional guidance.

If there is a set of boxes, some of which should be ticked and others left empty, then judge the entire set of boxes. If there is at least one tick, ignore crosses. If there are no ticks, accept clear, unambiguous indications, e.g. shading or crosses. Credit should be given for each box correctly ticked. If more boxes are ticked than there are correct answers, then deduct one mark for each additional tick. Candidates cannot score less than zero marks.

E.g. If a question requires candidates to identify a city in England, then in the boxes

Edinburgh Manchester Paris Southampton

the second and fourth boxes should have ticks (or other clear indication of choice) and the first and third should be blank (or have indication of choice crossed out).

Edinburgh Manchester × Paris Southampton × Score: 2 2 1 1 1 1 0 0 0 NR


Question Expected Answer Mark Additional Guidance 1 a i more can be grown (1) [1] allow cotton can be planted again ii any two from:

reference to using fertilisers; reference to using pesticides; cotton is bleached (using harmful chemicals);

[2]

iii these polymers are made from crude oil (1) (crude) oil/polymers are finite/will one day run out/is not renewable (1)

[2]

b they are easier to use/more convenient / they do not need to be washed / they are kinder to a baby's skin (1)

[1] allow more comfortable for baby / less likely to leak do not allow economy answers

c i from getting the raw material used to make the product to the disposal of the product (1)

[1] do not allow answers that start from making product from raw material

ii any two from: making materials; making the products from the materials; using the products; disposing of the products;

[2]

d i raw material production (1) manufacture of components (1)

[2]

ii (generation) of electricity used(1) manufacture of detergent (1)

[2]

Total [13]

3


Question Expected Answer Mark Additional Guidance

2 a i alcohols (1) [1] ii C2H6O (1) [1] accept C2H5OH b liquid;

yes; yes no

[3] all four correct = 3 marks three correct = 2 marks two correct = 1 mark

c i sugar/glucose (1) [1] ii (high concentration of) ethanol kills yeast (1) [1] allow the ethanol denatures/destroys the yeast

allow ethanol denatures enzymes but do not allow kills enzymes

iii distillation (1) plus any two from: mixture is heated/evaporated/boiled; vapour cooled to condense it; ethanol has lower boiling point (so boils off first);

[3] allow fractional distillation allow explanation marks independent of name but do not give marks for a method that does not separate eg reflux

Total [10] 3 a i energy level of reactants is higher than that of products (1)

so energy/heat given out during the reaction (1) [2] allow energy level at end is lower than at beginning /

energy level goes down / energy change is negative ii methane + oxygen → carbon dioxide + water (1) [1] Accept symbol equation if correct b taken in/gained/endothermic

given out/released/exothermic [1] both required for the mark

c energy needed to start a reaction (1) energy needed to break bonds (1)

[2] allow first mark for energy needed for a reaction to take place/begin / energy needed for successful collisions ignore reference to catalysts

Total [6]

4



4 a any three from: put spots of dyes (on origin); put end of paper in water; in a beaker; leave; until water is nearly at the top of the paper; observe how far dyes have travelled; QWC mark is for an answer that contains at least ten words with no more than one incorrect spelling in each ten words

[3]

[1]

allow other acceptable containers

b i maximum position of solvent travel (1) [1] ii pen ink smudges/runs/dissolves in the water (1) [1] c i C (1) [1] ii one spot from C travelled same distance up paper as the

spot from the banned compound (1) [1] allow C has a spot at the same level as banned

compound iii distance travelled by solvent (1)

distance travelled by (banned) dye (1) [2]

Total [10] 5 a i measure out 25.0 cm3 of the stock solution (1)

make up to 250 cm3 with (distilled/deionised) water (1) [2] allow one mark for adding 1 part stock solution to 9

parts water ignore references to dilution to a tenth of stock concentration

ii g/dm3 (1) [1] b i not accurate (1) [1] ii pipette (1) [1] allow burette iii to give a colour change (1)

when the alkali has been neutralised / when the solution is neutral (1)

[2] allow to determine the end point = 2 marks allow fully reacted

Total [7]

5


6


6 a i a chemical that is made in large quantities (1) [1] ii (to show that) the reaction is reversible / goes backwards

and forwards (1) [1] allow to show that it is a (dynamic) equilibrium

b air makes the process (more) sustainable(1) because the supply of air is not limited / air is renewable(1) natural gas makes the process less/not sustainable(1) because it is finite/will one day run out/not renewable(1)

[4]

c speed up the reaction (1) [1] accept provides an alternative route / lowers activation energy

d any two from: tanker vessel must be strong/pressurised/have thick walls; tanker vessel must be leak proof; tanker must carry a hazard warning sign; speed limits for heavy vehicles;

[2] allow no naked flames

Total [9]

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*OCE/16018*


TWENTY FIRST CENTURY SCIENCE A323/02CHEMISTRY AUnit 3: Ideas in Context plus C7 (Higher Tier)

H


• Write your name clearly in capital letters, your Centre Number and Candidate Number in the boxes above.• Use black ink. Pencil may be used for graphs and diagrams only.• Read each question carefully and make sure that you know what you have to do before starting your answer.• Answer all the questions.• Do not write in the bar codes.• Write your answer to each question in the space provided. Additional paper may be used if necessary but

you must clearly show your Candidate Number, Centre Number and question number(s).



your answer.


* A 3 2 3 0 2 *


© OCR 2010 [D/103/3792]DC (SJF5581/CG) 16018/4

Candidates answer on the Question PaperA calculator may be used for this paper



Friday 28 May 2010Morning


2

© OCR 2010


1 This question is based on the article ‘Which nappy is best for the environment?’

(a) Both disposable and reusable ‘terry’ nappies contain cellulose fibres from cotton. Cotton is generally considered to be a renewable material.

Some people say that although cotton is a renewable material its use is not really sustainable because of the way that we grow it.

What information in the article supports this argument?

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

(b) Many parents think that reusable nappies cause less environmental damage than disposable nappies.

Despite this, most parents use disposable nappies.

Suggest a reason why they do this.

...................................................................................................................................................

.............................................................................................................................................. [1]

(c) The article says that a Life Cycle Assessment (LCA) follows the lifetime of a product ‘from cradle to grave’.

Explain what this means.

...................................................................................................................................................

.............................................................................................................................................. [1]

(d) Use information from the article to describe and explain one environmental impact that is greater for reusable nappies than disposable nappies.

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

3


(e) It might be possible to use the recycling process mentioned in the article to recycle materials from all of the disposable nappies used in the UK.

Suggest why this would be difficult to achieve.

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [3]

(f) Disposable nappies contain the polymers polyethene and polypropene.

(i) These polymers melt at low temperatures. This enables the recycled polymers to be melted and made into new products.

Use ideas about forces and energy to explain why these polymers melt at low temperatures.

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(ii) A polymer with a lower melting point than polyethene might be easier to recycle.

Describe one method that may be used to produce a polymer with a lower melting point and explain how it does this.

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

[Total: 13]

4

© OCR 2010

2 A teacher drops a small piece of sodium into a dish of ethanol.

The teacher repeats this demonstration with sodium and water, and then with sodium and the liquid alkane, hexane.

(a) The table below is to record the observations made by a student watching the demonstration.

Complete the table by writing in each empty box what the student sees.

sodium + ethanol sodium + water sodium + hexane

[4]

(b) The diagrams show the structural formulae of ethanol, water and hexane.

CH

H

H

C O OH

H

H

H

H

ethanol water

CH

H

H

C

H

H

hexane

C

H

H

C

H

H

C

H

H

C

H

H

H

Explain the similarities and differences in the reactions of these three compounds with sodium.

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

5


(c) A dilute solution of ethanol can be made by fermentation of grape juice using yeast.

(i) Why is it not possible to make a concentrated solution of ethanol by fermentation?

...........................................................................................................................................

...................................................................................................................................... [1]

(ii) Name the method used to separate ethanol from the solution, and explain how it works.

method: .............................................................................................................................

explanation: .......................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [3]

[Total: 10]

6

© OCR 2010

3 Look at this energy level diagram for the complete combustion of methane in air.

energy level

energydifference

methane + oxygen

carbon dioxide + water

course of reaction

(a) The complete combustion of methane in air is an exothermic reaction.

How does the energy level diagram show that this reaction is exothermic?

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

(b) A mixture of methane and oxygen at room temperature does not react.

When a lighted match is applied the mixture burns.

The lighted match supplies the activation energy for the reaction.

Explain what is meant by the term activation energy.

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

7


(c) Methane burns in air according to this equation.

CH4 + 2O2 CO2 + 2H2O

The table shows the energy required to break each of the bonds involved in this reaction.

bond energy in kJ/mol

C–H 435

O=O 498

C=O 805

H–O 464

The energy used when the bonds in this reaction are broken can be calculated as follows.

4 × C–H = 4 × 435 = 1740 kJ/mol

2 × O=O = 2 × 498 = 996 kJ/mol

energy used = 1740 + 996 = 2736 kJ/mol

(i) Calculate the energy released as new bonds are made in this reaction.

energy released = ..............................................kJ/mol [3]

(ii) Calculate the overall energy change for the reaction.

overall energy change = ..............................................kJ/mol [1]

[Total: 8]

8

© OCR 2010

4 A scientist employed by the Food Standards Agency uses paper chromatography. He tests samples of water-soluble food dyes to see if they contain a banned compound.

The resulting chromatogram is shown below.

A B C D bannedcompound

dyes

start line

solvent front

1 cm

2

3

4

5

6

7

(a) The chromatogram shows that dye C contains the banned compound.

The identity of this substance can be confirmed using its published Rf value.

(i) Calculate the Rf value for the banned compound.

You must show your working.

Rf value =

distance travelled by solutedistance travelled by solvent

Rf value = ......................................................... [2]

9


(ii) Suggest why Rf values are sometimes a better way to compare spots on different chromatograms than a simple visual comparison.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(b) Describe how compounds in the dyes are separated during the chromatography.

Use the terms stationary phase, mobile phase and dynamic equilibrium in your answer.

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [3]

[Total: 7]

10

© OCR 2010

5 A student uses a titration with nitric acid to find the concentration of a solution of sodium hydroxide.

(a) The student has a stock solution of nitric acid containing 63 g in each dm3.

She uses this to make up 250 cm3 of a standard solution containing 6.3 g in each dm3.

Describe how she makes up this standard solution.

(1dm 3 = 1000 cm3)

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

(b) The student adds the standard nitric acid solution from a burette into sodium hydroxide solution in a flask.

She uses five 25.0 cm3 samples of the sodium hydroxide solution.

She obtains the following titration results.

titration number 1 2 3 4 5

volume ofnitric acid in cm3 28.3 28.2 28.2 28.1 28.2

(i) The student uses the average of her titration results, 28.2 cm3, as the best estimate of the volume of nitric acid used.

Show by calculation that the mass of nitric acid in 28.2 cm3 of the standard solution is 0.178 g.

[1]

11


(ii) Nitric acid and sodium hydroxide react according to the following equation.

HNO3 + NaOH NaNO3 + H2O

The relative formula mass of nitric acid is 63 and the relative formula mass of sodium hydroxide is 40.

Calculate the mass of sodium hydroxide in 25.0 cm3 of the sodium hydroxide solution, and hence find the concentration of the sodium hydroxide solution in g/dm3.

You should show your working.

mass of the sodium hydroxide in 25 cm3 solution = ............................. g

concentration of sodium hydroxide solution = ............................. g/dm3 [3]

(iii) Use the titration results to assess the degree of uncertainty in your value for the concentration of the sodium hydroxide solution.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

[Total: 8]

12

© OCR 2010

6 Ammonia is a bulk chemical made by the reaction of nitrogen with hydrogen.

N2 + 3H2 2NH3

The reaction is reversible, forming a dynamic equilibrium.

The diagram shows a flow chart of the Haber process for the manufacture of ammonia.

hydrogen

nitrogen

85% recycled

15%

reaction vessel air

natural gas and water

ammonia iron catalyst

high pressure450 °C

(a) Air and natural gas are used to make ammonia.

Suggest how each of these raw materials affects the sustainability of the process.

air ..............................................................................................................................................

...................................................................................................................................................

natural gas ................................................................................................................................

.............................................................................................................................................. [4]

(b) The process uses an iron catalyst. A catalyst speeds up the rate of conversion of reactants to products.

Use ideas about energy to explain how a catalyst works.

One mark is for using the correct scientific terms.

...........................................................................................................................................

...........................................................................................................................................

.................................................................................................................................. [2+1]

(c) Although the reaction is reversible, all of the nitrogen and hydrogen are eventually converted to ammonia.

Use the flow chart to explain how this is achieved.

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

[Total: 9]


13

© OCR 2010

BLANK PAGE


14

© OCR 2010

BLANK PAGE


15

© OCR 2010





For queries or further information please contact the Copyright Team, First Floor, 9 Hills Road, Cambridge CB2 1GE.


16

© OCR 2010

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GCSE

Chemistry A General Certificate of Secondary Education A323/02

Unit 3: Ideas in Context plus C7

Mark Scheme for June 2010

OCR (Oxford Cambridge and RSA) is a leading UK awarding body, providing a wide range of qualifications to meet the needs of pupils of all ages and abilities. OCR qualifications include AS/A Levels, Diplomas, GCSEs, OCR Nationals, Functional Skills, Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT, business, languages, teaching/training, administration and secretarial skills. It is also responsible for developing new specifications to meet national requirements and the needs of students and teachers. OCR is a not-for-profit organisation; any surplus made is invested back into the establishment to help towards the development of qualifications and support which keep pace with the changing needs of today’s society. 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 marks were awarded by Examiners. It does not indicate the details of the discussions which took place at an Examiners’ meeting before marking commenced. 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 should be read in conjunction with the published question papers and the Report on the Examination. OCR will not enter into any discussion or correspondence in connection with this mark scheme. © OCR 2010 Any enquiries about publications should be addressed to: OCR Publications PO Box 5050 Annesley NOTTINGHAM NG15 0DL Telephone: 0870 770 6622 Facsimile: 01223 552610 E-mail: [email protected]





3. Accept any clear, unambiguous response which is correct, e.g. mis-spellings if phonetically correct (but check additional guidance).


/ = alternative and acceptable answers for the same marking point (1) = separates marking points not/reject = answers which are not worthy of credit ignore = statements which are irrelevant - applies to neutral answers allow/accept = answers that can be accepted (words) = words which are not essential to gain credit words = underlined words must be present in answer to score a mark ecf = error carried forward AW/owtte = alternative wording ORA = or reverse argument E.g. mark scheme shows ‘work done in lifting / (change in) gravitational potential energy’ (1) work done = 0 marks work done lifting = 1 mark change in potential energy = 0 marks gravitational potential energy = 1 mark

5. Annotations: The following annotations are available on SCORIS.

= correct response = incorrect response bod = benefit of the doubt nbod = benefit of the doubt not given ECF = error carried forward ^ = information omitted I = ignore R = reject



1


2

E.g. For a one mark question, where ticks in boxes 3 and 4 are required for the mark:


This would be worth 0 marks.





8. The list principle: If a list of responses greater than the number requested is given, work through the list from the beginning. Award one mark for each correct response, ignore any neutral response, and deduct one mark for any incorrect response, e.g. one which has an error of science. If the number of incorrect responses is equal to or greater than the number of correct responses, no marks are awarded. A neutral response is correct but irrelevant to the question.



If there is a set of boxes, some of which should be ticked and others left empty, then judge the entire set of boxes. If there is at least one tick, ignore crosses. If there are no ticks, accept clear, unambiguous indications, e.g. shading or crosses. Credit should be given for each box correctly ticked. If more boxes are ticked than there are correct answers, then deduct one mark for each additional tick. Candidates cannot score less than zero marks.



the second and fourth boxes should have ticks (or other clear indication of choice) and the first and third should be blank (or have indication of choice crossed out).



Question Expected Answer Mark Additional Guidance 1 a any two from:

reference to using fertilisers (1) reference to using pesticides (1) cotton is bleached (using harmful chemicals) (1)

[2]

b they are easier to use/more convenient / they do not need to be washed / they are kinder to a baby's skin (1)

[1] allow more comfortable for baby / less likely to leak do not allow economy answers

c from getting the raw material used to make the product to the disposal of the product (1)

[1] do not allow answers that start from making product from raw material

d description: electricity/detergent used for washing (1) explanation: generating electricity causes pollution / detergent released into rivers etc (1)

[2] allow use of energy instead electricity allow any reasonable explanation of how this causes environmental impact

e not everyone would collect used nappies for recycling / may be difficult to collect all used nappies (1) there are not enough recycling plants available / so many nappies are used that this would be difficult (1) there may not be enough demand for the materials produced by recycling (1)

[3] three areas for marks: collection huge volume demand for products

f i forces (of attraction) between polymer chains/molecules are low (1) so little energy is needed to separate the chains/molecules (1)

[2] for the first mark candidates must write about forces between chains/molecules not bonds for second mark allow reference to breaking bonds between chains/molecules as long as energy mentioned ignore references to short chains

ii decrease chain length / decrease crystallisation / add plasticizer / decrease density (1) to decrease forces/attraction between chains/molecules (1)

[2] allow make branched polymer allow decreases number/strength of bonds between chains/molecules ignore references to less energy needed

Total [13]

3



2 a sodium + ethanol (slow) fizzing / dissolves / gets smaller / moves slowly across the surface (1) sodium + water (fast) fizzing / dissolves (quickly) / gets smaller (quickly) / shoots around on surface / melts / produces flame (1) sodium + hexane no reaction (1) answer shows that reaction with water is more vigorous than that with ethanol (1)

[4] one mark each for a valid observation for each of the three demonstrations if a mixture of valid and non-valid observations are made this loses the mark for that box plus one additional mark for a correct comparison of the same observation with ethanol and with water allow bubbling=fizzing=hydrogen/gas given off

b similarity: ethanol and water have O-H group/same functional group/oxygen and so react in a similar way (1) difference: hexane has only carbon and hydrogen atoms/does not have an O-H group/does not have oxygen and so does not react (1)

[2] allow water and ethanol have polar bonds allow hexane is a hydrocarbon/has unreactive C-C and C-H bonds and so does not react to score the answers must refer to the reactions not just to the structures

c i (high concentration of) ethanol kills yeast (1) [1] allow the ethanol denatures/destroys the yeast allow ethanol denatures enzymes but do not allow kills enzymes

ii distillation (1) plus any two from: mixture is heated/evaporated/boiled (1) vapour cooled to condense it (1) ethanol has lower/different boiling point (so is collected on its own/separately) (1)

[3] allow fractional distillation allow explanation marks independent of name but do not give marks for a method that does not separate eg reflux ignore ethanol has low boiling point

Total [10]

4



3 a energy level of reactants is higher than that of products (1) so energy/heat given out during the reaction (1)

[2] allow energy level at end is lower than at beginning / energy level goes down / energy change is negative

b energy needed to start a reaction (1) energy needed to break bonds (1)

[2] allow first mark for energy needed for a reaction to take place/begin / energy needed for successful collisions ignore reference to catalysts

c i (2 x 805 =) 1610 (1) (4 x 464 =) 1856 (1) energy released = 3466 (1)

[3] allow 3 marks for 3466 without working (even if not on answer line) ignore if go on to calculate 730 here

ii 730 (1) [1] ignore sign (plus or minus) allow ecf from ci give mark for 730 without working

Total [8] 4 a i 4.8 (1)

divided by 7.0 = 0.69 (1) [2] give 2 marks for correct answer without working

do not allow 4.9 or 0.7 allow 0.68 or 0.685 or 0.686 (max 3 sf)

ii Rf value is always the same for each compound (1) distance travelled by spot/solvent front may be different on different chromatograms (1)

[2] allow can be used to identify compound ignore reference to accuracy/precision

b stationary phase is paper and mobile phase is solvent / mobile phase moves up through stationary phase (1) for each compound there is a dynamic equilibrium between the two phases (1) how far each compound moves depends on its distribution between the two phases / if the compound is more soluble in the mobile phase it will move further up the paper (1)

[3] for third mark allow compounds travel different distances because they have different solubility in phases / dynamic equilibrium is more to one side / spend different amounts of time in the two phases

Total [7]

5


6


5 a measure out 25.0 cm3 of the stock solution (1) make up to 250 cm3 with (distilled/deionised) water (1)

[2] allow one mark for adding 1 part stock solution to 9 parts water ignore references to dilution to a tenth of stock concentration

b i 28.2 x 6.3/1000 = 0.178 (1) [1] be careful not to give this mark just for getting 0.178 the mark is for the correct method used to get 0.178 do not allow a mark for eg 28.2 x 6.3/100 = 0.178

ii 0.178 x 40/63 (1) = 0.113 (1) 0.113 x 1000/25 = 4.52 (1)

[3] allow any correct method for working eg 40 x 6.3/63 x 28.2/1000 allow 0.113 without working for 2 marks allow ecf from mass to concentration ie x40

iii uncertainty is low / value is reliable (1) because titration results show little variation/are very close/are within 0.2/have small range (1)

[2] ignore references to accuracy ignore references to outliers

Total [8] 6 a air makes the process (more) sustainable (1)

because the supply of air is not limited / air is renewable (1) natural gas makes the process less/not sustainable (1) because it is finite/will one day run out/not renewable (1)

[4]

b catalyst provides an alternative route (1) with a lower activation energy / less energy needed to begin the reaction / less energy needed to break bonds (1) QWC is for correct use of the term activation energy (1)

[2]

[1]

do not allow marks for other explanations of how a catalyst works ignore references to collisions

c reactants/nitrogen and hydrogen that have not reacted are recycled (1) ammonia is removed so the system does not reach equilibrium/reverse reaction is not possible/pushes equilibrium to the right (1)

[2] no mark simply for saying 85% recycled, must have idea that this gas has not reacted / goes back to react

Total [9]

*OCE/V00670*


TWENTY FIRST CENTURY SCIENCE A323/01CHEMISTRY AUnit 3: Ideas in Context plus C7(Foundation Tier)

F


• Write your name clearly in capital letters, your Centre Number and Candidate Number in the boxes above.• Use black ink. Pencil may be used for graphs and diagrams only.• Read each question carefully and make sure that you know what you have to do before starting your answer.• Answer all the questions.• Do not write in the bar codes.• Write your answer to each question in the space provided, however additional paper may be used if

necessary.



your answer.


* A 3 2 3 0 1 *


© OCR 2009 [D/103/3792]SP (CW/SW) V00670/4

Candidates answer on the question paperA calculator may be used for this paper



Thursday 4 June 2009Morning


2

© OCR 2009


1 This question is based on the article ‘The bioethanol dilemma’.

(a) (i) The article suggests that most bioethanol produced in the UK would be made from wheat.

Name two other fuel crops mentioned in the article that are used to make bioethanol.

1 ................................................

2 ................................................ [1]

(ii) The table in the article shows how bioethanol consumption increased in a number of European countries from 2005 to 2006.

In which country did bioethanol consumption have the biggest increase?

................................................... [1]

(b) Describe two of the environmental benefits of burning bioethanol, compared to petrol, that are mentioned in the article.

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

(c) (i) The European Union expects biofuels to meet 5.75% of transport fuel needs by 2010.

Soon most petrol sold in the UK will contain some bioethanol.

It is not likely that petrol will contain more than 5% bioethanol in the near future.

Suggest why.

...........................................................................................................................................

...................................................................................................................................... [1]

(ii) In the more distant future, cars may be fuelled by 100% bioethanol.

A typical driver in the UK drives 600 000 miles in their lifetime.

How many hectares of wheat would need to be grown to produce bioethanol to fuel a car for the total mileage driven by this typical driver?

.............................hectares of wheat [1]

3


(d) (i) The article suggests that as demand for bioethanol increases, food prices will rise.

Suggest why.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [1]

(ii) The article also suggests that as demand for bioethanol increases, there will be a decline in soil fertility.

This will result in farmers using more fertilizers.

Suggest why using more fertilizers might harm the environment.

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(e) (i) List two factors mentioned in the article that are involved in the Life Cycle Assessment for bioethanol that do not apply to petrol.

1 ........................................................................................................................................

...........................................................................................................................................

2 ........................................................................................................................................

...................................................................................................................................... [2]

(ii) Explain how bioethanol may be a more sustainable fuel than petrol.

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

[Total: 13]

4

© OCR 2009

2 Methanoic acid is a carboxylic acid that is released in bee stings.

(a) The diagram shows the structural formula of methanoic acid.

H

H C

O

O

On the diagram, draw a circle around the functional group that is responsible for the characteristic properties of carboxylic acids. [1]

(b) Methanoic acid is used to remove the limescale that can build up in kettles. Limescale is made of calcium carbonate, which is insoluble in water.

Carboxylic acids react with carbonates in a similar way to other acids, such as hydrochloric acid.

calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water

(i) Complete this word equation for the reaction between methanoic acid and calcium carbonate.

+ calciummethanoate

+ + [2]

(ii) Suggest a property of calcium methanoate that explains how this reaction removes limescale.

...........................................................................................................................................

...................................................................................................................................... [1]

(iii) Some kettles have metal bodies, and all have metal heating elements.

Hydrochloric acid is not used to remove limescale from kettles.

Explain why methanoic acid is used to remove limescale but hydrochloric acid is not.

Use ideas about strong and weak acids in your answer.


...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

.................................................................................................................................. [3+1]

5


(c) Ethanoic acid, CH3COOH, is another carboxylic acid, present in vinegar.

Draw a diagram to show the structural formula for ethanoic acid.

[2]

[Total: 10]

6

© OCR 2009

3 Vegetable oils are commonly used in cooking. Examples are rape seed oil and sunflower seed oil.

(a) These oils are found in the seeds produced by plants.

What is the job of the oil in these seeds?

.............................................................................................................................................. [1]

(b) (i) When an ester is hydrolysed it forms an alcohol and a carboxylic acid. This reaction is the reverse of that used to make the ester.

Oils and fats are esters. Write the name of the alcohol and of the type of carboxylic acid to complete this word equation for the hydrolysis of an oil.

oil + water .......................................... + .......................................... [2]

(ii) What two things does the sign tell you about this reaction?

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(c) In addition to vegetable oil, a food product may contain other esters.

Suggest two reasons why other esters may be added to food products.

...................................................................................................................................................

.............................................................................................................................................. [2]

[Total: 7]

7


BLANK PAGE


Question 4 starts on page 8.

8

© OCR 2009

4 A technician carries out an analysis of a mixture of hydrocarbons using gas chromatography.

She first calibrates the equipment using standard hydrocarbons. The retention times for these hydrocarbons are shown in the table.

hydrocarbon retention timein min

methane 1.7

ethane 2.2

propane 3.5

propene 4.0

butane 7.4

The technician then analyses the mixture of hydrocarbons. The recorder print-out from this analysis is shown below.

0

100

0 1.0 2.0 3.0

retention time in min

recorderresponse

4.0 5.0 6.0 7.0 8.0

(a) Explain what is meant by the term retention time.

...................................................................................................................................................

.............................................................................................................................................. [2]

9


(b) (i) Which three hydrocarbons are present in the mixture?

1 ................................................

2 ................................................

3 ................................................ [2]

(ii) Name the hydrocarbon that has the highest concentration in the mixture.

...................................................................................................................................... [1]

(iii) One of the gases in the mixture is not an alkane.

What is the name of this gas?

...................................................................................................................................... [1]

(c) Two of the hydrocarbons in the mixture are alkanes.

Alkanes burn but they do not react with solutions of other chemicals, for example bromine water.

(i) Explain why alkanes do not react with bromine water.

Use ideas about the bonds in alkanes in your answer.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(ii) The burning of alkanes gives out energy.

Use ideas about bond making and breaking to explain why.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

[Total: 10]

10

© OCR 2009

5 Some indigestion tablets contain the active ingredient, magnesium hydroxide. This reacts with excess stomach acid to relieve the symptoms of acid indigestion.

Mg(OH)2 + 2HCl MgCl2 + 2H2O

The tablets also contain starch.

A chemist uses quantitative analysis to find the mass of active ingredient in each tablet.

(a) The statements describe the main stages of this analysis, but they are in the wrong order.

A Crush the tablet and stir it into approximately 25 cm3 distilled water.

B Use the average titration result to calculate the mass of magnesium hydroxide in each tablet.

C Titrate the mixture against hydrochloric acid of known concentration.

D Measure accurately the mass of one indigestion tablet.

E Estimate the degree of uncertainty in the result.

F Repeat the procedure using several more tablets.

Write letters in the boxes to show the correct order of the stages. The correct letter has already been written in the first box.

D

[3]

(b) What apparatus should the chemist use to measure each of the following?

(i) The 25 cm3 distilled water.

...................................................................................................................................... [1]

(ii) The volume of hydrochloric acid used in each titration.

...................................................................................................................................... [1]

11


(c) The chemist finds that the average volume of hydrochloric acid used to react with the magnesium chloride in a tablet is 23.5 cm3.

(i) The relative formula mass of hydrochloric acid is 36.5.

Work out the relative formula mass (RFM) of magnesium hydroxide, Mg(OH)2.


(relative atomic masses: H = 1, Mg = 24, O = 16)

relative formula mass (RFM) of magnesium hydroxide = ......................................................... [2]

(ii) Use this formula to work out the mass of magnesium hydroxide in each indigestion tablet.

mass of magnesium hydroxide = volume HCl × 40 × RFM Mg(OH)2

2000 × 36.5

mass of magnesium hydroxide in each tablet = ...................................................... g [1]

[Total: 8]

12

© OCR 2009

6 Epoxyethane, (CH2)2O, is an intermediate in the production of car anti-freeze, and is used to sterilize medical supplies.

H H

HH

O

epoxyethane

C C

Epoxyethane is poisonous, carcinogenic and highly flammable.

The raw material used to make epoxyethane is ethene. This is obtained by the cracking of hydrocarbons from petroleum.

(a) (i) Epoxyethane is a bulk chemical.

Explain what is meant by the term ‘bulk’.

...........................................................................................................................................

...................................................................................................................................... [1]

(ii) The manufacture of epoxyethane may not be sustainable to the end of this century.

Use information about the raw material used in its manufacture to suggest why.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(b) Two methods have been used to make epoxyethane.

• original method – from ethene, chlorine and calcium hydroxide

• modern method – ethene and oxygen are passed over a silver catalyst at 250-350 °C

(i) The original method produces solid calcium chloride as a by-product, but the modern method does not.

There is little use for this calcium chloride.

Explain why this makes the original method less sustainable than the modern method.

...........................................................................................................................................

...................................................................................................................................... [1]

13

© OCR 2009

(ii) The catalyst in the modern method consists of very fine particles.

Explain why.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(c) The government has strict regulations that control the way that epoxyethane is made, stored and transported.

What is the purpose of these regulations?

...................................................................................................................................................

.............................................................................................................................................. [1]

[Total: 7]


14

© OCR 2009

BLANK PAGE


15





For queries or further information please contact the Copyright Team, First Floor, 9 Hills Road, Cambridge CB2 1PB.



16

© OCR 2009

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GCSEChemistry A

Twenty First Century Science

General Certificate of Secondary Education J634

Mark Scheme for the Units June 2009

J634/MS/R/09

OCR (Oxford Cambridge and RSA) is a leading UK awarding body, providing a wide range of qualifications to meet the needs of pupils of all ages and abilities. OCR qualifications include AS/A Levels, GCSEs, OCR Nationals, Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT, business, languages, teaching/training, administration and secretarial skills. It is also responsible for developing new syllabuses to meet national requirements and the needs of students and teachers. OCR is a not-for-profit organisation; any surplus made is invested back into the establishment to help towards the development of qualifications and support which keep pace with the changing needs of today’s society. 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 marks were awarded by Examiners. It does not indicate the details of the discussions which took place at an Examiners’ meeting before marking commenced. 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 should be read in conjunction with the published question papers and the Report on the Examination. OCR will not enter into any discussion or correspondence in connection with this mark scheme. © OCR 2009 Any enquiries about publications should be addressed to: OCR Publications PO Box 5050 Annesley NOTTINGHAM NG15 0DL Telephone: 0870 770 6622 Facsimile: 01223 552610 E-mail: [email protected]

CONTENTS

GCSE Twenty First Century Science – Chemistry A (J634)

MARK SCHEMES FOR THE UNITS

Unit/Content Page Guidance for Examiners 1

A321/01 Modules C1, C2, C3 Foundation Tier 3

A321/02 Modules C1, C2, C3 Higher Tier 12



A323/01 Unit 3 Ideas in Context plus C7 Foundation Tier 42

A323/02 Unit 3 Ideas in Context plus C7 Higher Tier 46

Grade Thresholds 53

J634 Mark Scheme June 2009

1




3. Accept any clear, unambiguous response which is correct, eg mis-spellings if phonetically correct (but check additional guidance).


/ = alternative and acceptable answers for the same marking point (1) = separates marking points not/reject = answers which are not worthy of credit ignore = statements which are irrelevant - applies to neutral answers allow/accept = answers that can be accepted (words) = words which are not essential to gain credit words = underlined words must be present in answer to score a mark ecf = error carried forward AW/owtte = alternative wording ORA = or reverse argument Eg mark scheme shows ‘work done in lifting/(change in) gravitational potential energy’ (1) work done = 0 marks work done lifting = 1 mark change in potential energy = 0 marks gravitational potential energy = 1 mark




7. The list principle: If a list of responses greater than the number requested is given, work through the list from the beginning. Award one mark for each correct response, ignore any neutral response, and deduct one mark for any incorrect response, eg one which has an error of science. If the number of incorrect responses is equal to or greater than the number of correct responses, no marks are awarded. A neutral response is correct but irrelevant to the question.



If there is a set of boxes, some of which should be ticked and others left empty, then judge the entire set of boxes. If there is at least one tick, ignore crosses. If there are no ticks, accept clear, unambiguous indications, eg shading or crosses. Credit should be given for each box correctly ticked. If more boxes are ticked than there are correct answers, then deduct one mark for each additional tick. Candidates cannot score less than zero marks.

Eg If a question requires candidates to identify a city in England, then in the boxes


the second and fourth boxes should have ticks (or other clear indication of choice) and the first and third should be blank (or have indication

of choice crossed out).


2


3

A321/01 Modules C1, C2, C3 Foundation Tier

Question Expected Answers Marks Rationale 1 a

nitrogen monoxide

CO

carbon

monoxide

NO

water vapour SO2

sulfur

dioxide H2O

4

Mark left and right hand sides independently Matching name to formula – two marks for all correct, one mark for two or three correct. (max 2) Matching formula to molecule – two marks for all correct, one mark for two or three correct (max 2) If 2 lines leave or arrive at one box then the mark is lost

b i sulfur dioxide/nitrogen monoxide/SO2/NO

1 either formula must be correct if used

ii carbon monoxide/CO

1 formula must be correct if used

iii water (vapour)/H2O


Total 7



... reliable results (1)

1

3rd box

b i

... well outside the range ... (1)

1

2nd box

ii

... wind changed direction ... (1)

... burned less coal ... (1)

2

4th and 5th boxes

4


Question Expected Answers Marks Rationale 2 c 311;

297 to 322;

2 one mark for each correct answer accept 314/314.5/315 for the mean If 314/314.5/315 is given for the mean then allow 307 to 322 for the range Numbers for a range can be given in either order

d decreases decreases OR increases increases

1

both correct words required – (must be same word used twice)

Total 7

5



... using the spoon (1)

1 3rd box

b

Supply of metal ores is finite. (1)

More trees can be planted ... (1)

Plastics made from crude oil ... (1)

3

2nd, 4th and 6th boxes

6


Question Expected Answers Marks Rationale 3 c

... metal spoon not stained... (1)

... plastic spoon too soft ... (1)

... wooden spoon stained ... (1)

3

2nd, 3rd and 5th boxes

Total 7

7



cotton polyester silk wool

1

correct word circled and no other words circled

b small; long; polymerisation;

3

one mark for each correct choice

c i

carbon (1)

hydrogen (1)

2

1st and 4th boxes

ii food fuels lubricants

1

Total 7

8


Question Expected Answers Marks Rationale 5 a i

Plants take nitrogen ... (1)

When crops are harvested ... (1)

2

2nd and 5th boxes

ii calcium carbon chlorine hydrogen neon oxygen sodium

2

all three correct words circled and no others circled for 2 marks two correct words circled for one mark marks are lost if more than three words are circled

b i Some crops naturally contain

toxic ... (1)

During storage, crops contaminated ... (1)

2 1st and 5th boxes

9


Question Expected Answers Marks Rationale 5 b ii

... safe levels of chemicals ... (1)

1 3rd box

Total 7

10



amino acids amino acids urine urea

4 one mark for each correct choice, correctly placed.

b

body no longer responds to its

own insulin

penicillin injections

type 1 insulin is

destroyed by the pancreas

diet and exercise

type 2 pancreas does

not produce enough insulin

insulin tablets

pancreas

produces too much insulin

insulin injections

2 one mark for each correct ‘row’ linking type of diabetes to both the correct description and the correct treatment More than one line leaving or arriving at a box loses the mark

c anorexia asthma obesity sunburn

1 one mark for the correct word and no other circled

Total 7

11


12

A321/02 Modules C1, C2, C3 Higher Tier


sulfur dioxide SO2

nitrogen monoxide NO

carbon monoxide CO

3

one mark for each correct row do not allow SO2/So2/sO2

do not allow sulfur oxide/sulfur monoxide/sulfur trioxide allow sulfur(IV) oxide do not allow nitrogen oxide/nitrogen dioxide/nitrous oxide allow nitric oxide/nitrogen(II) oxide do not allow No/nO do not allow carbon oxide/carbon dioxide allow carbon(II) oxide do not allow Co/cO

b [1] [3] [2] [2]

3

one mark for each correct number after [1]

Total 6




1

3rd box

b i


1

2nd box

ii



2

4th and 5th boxes

13



... ranges don’t overlap. (1)

... mean before is outside range after ... (1)

2

3rd and 5th boxes

d i A (1)

1 no mark if two or more letters are quoted

ii D (1) 1 no mark if two or more letters are quoted

Total 8

14




1 3rd box

b




3


15



... use and disposal ... (1)

... making the product from the material. (1)

2

2nd and 4th boxes

d

... available locally ...

It is easy to make wooden spoons ...

1

both 1st and 3rd boxes for one mark three or more boxes ticked = 0 marks

Total 7

16


Question Expected Answers Marks Rationale 4 a i B C D

1 one mark for any two of these three correct letters in any order

allow the mark if all three correct letters are given do not allow the mark if incorrect letter A is given

ii A D

1 one mark for both correct letters in either order do not allow the mark if more than two letters are given

iii A D


b

... less plasticizer ... (1)

Increase chain length ... (1)

2

1st and 5th boxes

c

... forces between the molecules.

… forces between the polymer chains stronger.

… but weak forces between …

2

all three of 1st, 4th and 5th boxes for two marks two boxes correct with or without a third incorrect one = one mark four boxes ticked = max one mark ie only gets the mark if all three correct boxes are included five or six boxes ticked = 0 marks

Total 7

17





2 2nd and 5th boxes

ii carbon (1) and hydrogen (1)

2 one mark for each correct word, in either order for three words max 1 mark, for four words no marks for hydrogen allow H or H2 but not h or h2 for carbon allow C but not C2 etc


toxic ... (1)


2 1st and 5th boxes

18



... easier to make ...

... more expensive ...

1 both 1st and 3rd boxes for one mark three or more boxes ticked = 0 marks

Total 7

19


Question Expected Answers Marks Rationale 6 a amino acids

liver urea kidney(s) urine

3 all five words correct for 3 marks four words correct for 2 marks three words correct for 1 mark do not allow monomers for amino acids

b

... pancreas does not produce enough ...

Sugar ... is quickly absorbed ...

... to regulate the amount of sugar ...

2 all three of 2nd, 3rd and 6th boxes for two marks two boxes correct with or without a third one incorrect for one mark four boxes ticked = max one mark ie only gets the mark if all three correct boxes are included five or six boxes ticked = 0 marks

20



the chance ... contracting type 2 ... (1)

the consequences of ... diabetes (1)

2 2nd and 5th boxes

Total 7

21


22


… reacts with cold water. … to form compounds. … quicker than potassium. … is very unstable.

2

all 4 correct = 2 2 or 3 correct = 1

1 correct = 0

Accept other indications of choice (eg lines or crosses)

b i protons (1) neutrons (1)

2

either order

ii 3 electrons arranged 2 inside the inner shell, 1 in the outer shell

1

Total 5

X

X

X


false

true



2 (1) mark for each correct line. If more than 2 lines are drawn, deduct (1) for each additional incorrect line.

ii

Do experiments in a fume cupboard. Do not breathe in the gas.

2 Accept other indications of choice (eg lines or crosses)

purple

dark grey

iodine gas

solid iodine

23


Question Expected Answers Marks Rationale 2 b

Iodine solution kills bacteria.


5

24



the colour of the flame


b

a fixed pattern of lines


c

potassium (1) chlorine (1)

2 either order accept any phonetic spellings reject 'chloride'

Total 4

25


Question Expected Answers Marks Rationale

4 a 1 If more than 1 box is ticked, 0 marks

b C and H only in the formula (1) Fully correct formula: C2H4 (2)

2 C and H must be capitals eg Ch4 scores (0) C2h4 scores (1)

allow H4C2/CH2CH2/H2C2H2/H2CCH2

Any number in front of formula, can only score first mark eg

2CH2 scores (1)

2 and 4 must be clearly subscripted or smaller than C and H eg C2H4 or C2H4 scores (1)

Total 3

26



5 a i

more more less

2 all 3 correct = 2 1 or 2 correct = 1 Allow other indications of choice eg underlining

ii

50-65% (1)

1

b 2 all 3 correct = 2 1 or 2 correct = 1 If more than 3 lines are drawn, deduct (1) for each additional incorrect line.

Total 5

good

easily bent

very

property

gold

jewellery

car air

use

27



6 a

Bubbles form around an electrode. The bulb lights up.

2 If more than 2 boxes are ticked, deduct one mark for each additional tick

b ionic (1) ions (1) positive (1)

3

c lead (1)

1 Allow led Allow correct symbol Pb Do not allow PB

Total 6

28



7 a i sulfuric (acid)/sulphuric (acid) (1)

1 accept phonetic spelling

ii magnesium carbonate (1) magnesium oxide (1)

2 If more than two compounds are ringed, deduct (1) for each additional incorrect compound. Allow other indications of choice eg underlining

b

use acid that is more dilute

1 If more than 1 box is ticked, 0 marks

Total 4

29



8 a

indicator paper


b 3

Total 4

chemical acidic … pH

neutral

8-10

1-2

30



9 a 3

b neutralisation (1)

1 If more than one answer is ringed, deduct (1) for each additional incorrect response. Allow other indications of choice eg underlining

c i 40 (1)

1

ii

She spilled some chemicals.


Total 6

hydrochloric acid (1) burette (1)

flask (1)

31


32



2 all 4 correct = 2 2 or 3 correct = 1 1 correct = 0 Accept other indications of choice (eg lines or crosses)

b Correct symbols: Li and O2(1) Correct balancing: 4Li + O2 (1)

2 Must have capital L and lower case i in Li and capital O with subscripted 2 in O2. Do not allow LI Top of the number 2 in O2 should not be above half the height of the O, Do not allow O2. Second mark can only be scored if formulae are correct. Allow second mark if small errors in formula eg 4Li + O2 scores (1) Allow 4Li + 1 O2

Any other number in front of O2 does not score this mark.

Total 4


falsetrue




ii


purple

dark grey

iodine gas

solid iodine

solid iodine

I2(g)

I2(s)

iodine gas

33



Iodine is in Group 7.

All Group 7 elements kill bacteria.

1 Both must be correct for (1) mark If more than two ticks, 0 marks

Total 5

34



… light of different colours. … very hot and so emit light.

2 If more than two ticks are given, deduct (1) mark for each additional incorrect tick. Allow other indications of choice.

b protons and neutrons named in either order (1)

correct numbers of protons and neutrons: 4 protons, 5 neutrons (1)

4 electrons in arrangement 2,2 (1)

3

Second mark cannot be scored if protons and neutrons not named. 4 neutrons and 5 protons scores first mark only (1) Allow phonetic spelling of protons and neutrons. eg two electrons anywhere in each ‘ring’. Allow other symbols for electrons eg e, - or o

Total 5

X

X

X

X

35


Question Expected Answers Marks Rationale 4 a 1 If more than 1 box is ticked, 0 marks


2 C and H must be capitals eg Ch4 scores (0) C2h4 scores (1) allow H4C2 / CH2CH2 / H2C2H2 / H2CCH2 Any number in front of formula, can only score first mark eg 2CH2 scores (1) 2 and 4 must be clearly subscripted or smaller than C and H eg C2H4 or C2H4 scores (1)

Total 3

36



Potassium iodide is an ionic compound. Ions in the liquid are free to move.


b lead (1)


c e—/e 1 Do not allow word ‘electron’

Total 4

37


Question Expected Answers Marks Rationale 6 a C (1) 1 Allow lower case

More than one letter scores 0

b A (1) 1 As above

c D (1) 1 As above

d

Electrons are shared between atoms. The nucleus of each bonded atom …


e MgF2 (1) 1 Must have capital M and lower case g in Mg and full size F with subscripted 2. Do not allow MGF2/Mg2F/MgF2 /Mg2F /F2Mg Top of the number 2 after F should not be above half the height of the F, Do not allow MgF2. Do not allow if any number is in front of formula eg 2MgF2 scores 0

Total 6

38


Question Expected Answers Marks Rationale 7 a i sulfuric (acid)/sulphuric (acid) (1) 1 accept phonetic spelling



b i

All the acid is used up.


ii

to get more magnesium sulfate …


39


Question Expected Answers Marks Rationale 7 b iii

… largest crystals. …as he heats it. … faster the crystals form. … solid salt evaporate.

2 All 4 correct = 2 2 or 3 correct = 1 1 correct = 0

c



Total 8

true false

40


Question Expected Answers Marks Rationale 8 a i A (1) 1 If more than one choice ringed, 0 marks

ii B and C (1) 1 both needed for the mark If more than two letters ringed, 0 marks

b K+ ringed and both K22+ and K2+ unringed (1)

SO4

2— ringed and both S2- and O2- unringed (1)

2

c

… produces a precipitate. … is a neutralisation reaction. … produces OH— ions. An equation for the reaction is … Hydrogen gas is given off.

3 All 5 correct = 3 4 correct = 2 2 or 3 correct = 1 1 correct = 0

Total 7

true false

41


42

A323/01 Unit 3 Ideas in Context plus C7 Foundation Tier

Question Expected Answers Marks Rationale 1 a i any two from:

corn; maize; sugar (beet);

1 both required for the mark

ii Austria (1) 1

b any two from: produces less carbon dioxide; requires less energy to produce; transport produces less pollution; it is sustainable; it is renewable; it is biodegradable; it is less toxic than fossil fuels; it produces less carbon monoxide/particulate carbon;

2

c i annual wheat surplus of 3.5 million tons would produce enough bioethanol for only about 5%/car engines will have to be modified to use more than 5% bioethanol/insufficient land space to produce the crop/use more wheat than surplus/reduces land space for food (1)

1

ii 20 hectares of wheat (1) 1

d i as more crops are grown for fuel less will be grown for food, causing a shortage (1)

1

ii fossil fuel will be used to produce the fertilizer (1) over use of fertilizer will cause water pollution (1)

2


Question Expected Answers Marks Rationale 1 e i any two from:

(energy used in/environmental impact of:) growing fuel crop/harvesting fuel crop/fuel crop is renewable; fermentation/processing into ethanol; decrease in soil fertility; effect on water supply; use of fertilizers;

2 ignore renewable unqualified

e ii petrol/crude oil is finite/not renewable (1) bioethanol is made from crops, which we can grow more of (1)

2 allow description of carbon cycle for bioethanol allow bioethanol is renewable

Total 13 Question Expected Answers Marks Rationale 2 a circle around COOH group (1) 1

b i methanoic acid + calcium carbonate (1) → calcium methanoate + carbon dioxide + water (1)

2

ii calcium methanoate is soluble (1) 1

iii methanoic acid is a weak acid (1) hydrochloric is a strong acid (1) hydrochloric acid will damage the kettle/methanoic acid will remove limescale without damaging the kettle (1) QWC - at least ten words with no more than one spelling error (1)

4

c structure of CH3 correct (1) structure of COOH correct (1)

2

Total 10

H O H C C H O H

43


Question Expected Answers Marks Rationale 3 a as an energy store (1) 1

b i glycerol (1) + fatty acids (1) 2 either order allow long chain carboxylic acids = fatty acids

ii reaction is reversible/reaction can go either way/reaction can go forwards and backwards (1) reaction reaches an equilibrium/all reactants and products are present in the reaction mixture (at equilibrium) (1)

2 allow it is a (dynamic) equilibrium allow forward and reverse rates are the same

c as flavouring/to improve taste (1) to give the required smell/to improve smell (1)

2

Total 7 Question Expected Answers Marks Rationale 4 a time from injection of sample (1)

until chemical leaves column/to appearance of peak/is detected (1)

2 time it takes to go through stationary phase is 2 marks

b i ethane propene butane 2 any order all correct = 2 marks 2 correct 1= 1 mark reject propane

ii propene (1) 1 reject propane

iii propene (1) 1 reject propane

c i any two from: they have unreactive C-C bonds; they have unreactive C-H bonds; they only have single bonds/they do not have double bonds/they are saturated;

2 allow they have unreactive bonds for 1 mark only ignore all their bonds are strong/C-C bonds are stronger than C=C bonds

ii bond making releases energy and bond breaking takes in energy (1) more energy is released than taken in (1)

2 allow as alternative words exothermic = releases energy, endothermic = takes in energy marks can be scored from an annotated energy level diagram

Total 10

44



D A C F B E

3 all 5 in correct order = 3 marks any 4 in correct order = 2 marks any 3 in correct order = 1 mark

b i measuring cylinder (1)

1 allow pipette

ii burette (1) 1

c i use of 24, 16 and 1 in calculation but processed incorrectly (1) 58 (1)

2 allow first mark for calculations otherwise correct but missing out a step eg 2 x 1 or 2 x 16 do not allow first mark for totally incorrect calculation eg 24 x 16 x 1 allow 2 marks for correct answer without working

ii 0.75 (1) 1 allow 0.747/0.746 allow ecf from 5(c)(i)

Total 8 Question Expected Answers Marks Rationale 6 a i a chemical made in large quantities (1)

1

ii it is made from ethene which is made from crude oil (1) crude oil/ethene is finite/crude oil/ethene will run out (1)

2

b i the calcium chloride must be dumped/the calcium chloride must be disposed of (1)

1 must imply that calcium chloride has to be disposed of – not just a waste product.

ii larger surface area (1) gives more contact with reactants (1)

2

c to protect people/to protect the environment/health and safety (1)

1 allow make safe allow harming others by misuse

Total 7

Paper Total 55

45


46

A323/02 Unit 3 Ideas in Context plus C7 Higher Tier

Question Expected Answers Marks Rationale 1 a pollution is caused/carbon dioxide is released by the

production process (1) it gives 70% of the mileage of petrol (1)

2 allow as bioethanol is made = production process ignore releases 34% less energy unless qualified allow eg it gives less miles (per gallon) than petrol

b this would use wheat/land that is now used for food/cause decline in soil fertility/decrease water supply/quality/increase fertiliser use (1) food prices would increase/there would be a food shortage/we would have to import more food (1) car engines would need to be modified (1)

2 Any two ignore uses a lot of land/would use too much land ignore references to decreasing habitats for animals ignore would have to import bioethanol

c these countries struggle to feed everyone/ need all their crops for food (1) making bioethanol will cause a food shortage/cause famine (1)

2 ignore references to land quality/rainfall/technology/cars/ignore copied statement ‘The amount of grain …. an African village’.

d RFM octane 114 and RFM carbon dioxide 44 (1) mass of carbon dioxide = (8x44)/114 = 3.1 g (1) percentage = 100 x (3.1-1.9)/1.9 = 63 or percentage = [(3.1/1.9) x 100] – 100 = 63 (1)

3 allow 352 for 44 (ie 8 x 44) allow 2 marks for correct mass of carbon dioxide alone allow 3.08 g/3.09 g/3.087 g/3.088 g allow any answer between 62.0 and 63.2 but do not allow an answer that is derived from incorrect working allow ecf from mass answer for % from 55 to 65 only do not give mark for 60% unless working gives 3.04 for mass


Question Expected Answers Marks Rationale 1 e i (energy used in/environmental impact of:)

growing fuel crop/harvesting fuel crop/fuel crop is renewable; fermentation/processing into ethanol; decrease in soil fertility; effect on water supply; use of fertilisers;

2 Any two ignore renewable unqualified

ii petrol/crude oil is finite/not renewable (1) bioethanol is made from crops, which we can grow more of (1)


Total 13

47


Question Expected Answers Marks Rationale 2 a COOH 1 allow CO2H

O allow C OH

b i

CaCO3 + 2HCOOH Ca(HCOO)2 + CO2 + H2O

2

one mark for all formulae correct, one mark for balance balance mark can only be scored if formulae correct allow molecular formulae subscript numbers must be clearly subscript or no marks

ii calcium methanoate is soluble (1)

1

iii a strong acid is completely ionised (1) a weak acid is only partly ionised (1) the weak acid has dynamic equilibrium/in a weak acid the equilibrium is far to the left/in a dynamic equilibrium the reaction does not go to completion (1) QWC - at least ten words with no more than one spelling error per ten words (1)

4 only give the third marking point if there is no suggestion that the strong acid also has a (dynamic) equilibrium ignore reaction goes in both directions QWC mark can be given if there has been a genuine attempt at an answer even if the chemistry has scored no marks

c H H H O H C C C C H H H O H

1 allow CH3 for methyl group/CH3CH2CH2COOH allow COOH for carboxyl group/OH instead of O-H allow correct structure with a circle around each atom reject molecule drawings using shaded circles to show atoms

Total 9

48


Question Expected Answers Marks Rationale 3 a i glycerol (1) + fatty acids (1)

2 either order

allow long chain carboxylic acids = fatty acids



b purification: product is shaken with reagent in a tap/separating funnel (1) impurities dissolve in reagent (which can be run off) (1) drying: solid drying agent is added to product (1) the drying agent absorbs water from the product (1)

4 allow named reagent eg distilled water ignore references to neutralisation allow named solid drying agent eg calcium chloride/sodium sulfate, do not allow calcium carbonate!

Total 8

49


Question Expected Answers Marks Rationale 4 a i propene

1 do not allow propane!

ii area under the peak is largest/area under peak shows concentration

1 allow highest/widest/longest ignore references to retention time

b the mobile phase carries the sample (1) components are differently attracted to the stationary and mobile phases (1) the components that are more strongly attracted to the stationary phase move more slowly/ora (1) the amount of each component in the stationary phase and in the mobile phase is determined by a dynamic equilibrium (1)

4 accept answers that are based on ideas of different concentrations/different time spent in each phase as alternative to attraction again accept answers that are based on ideas of different concentrations/different time spent in each phase as alternative to attraction

c i they have unreactive C-C bonds (1) they have unreactive C-H bonds (1) they only have single bonds/they do not have double bonds/they are saturated (1)

2 Any two allow they have unreactive bonds = 1 mark only ignore all their bonds are strong/C-C bonds are stronger than C=C bonds


2 allow as alternative words exothermic = releases energy , endothermic = takes in energy marks can be scored from an annotated energy level diagram

Total 10

50


Question Expected Answers Marks Rationale 5 a i use of 24, 16 and 1 in calculation but processed

incorrectly (1) 58 (1)

2 allow first mark for calculations otherwise correct but missing out a step eg 2x1 or 2x16 do not allow first mark for totally incorrect calculation eg 24x16x1 allow 2 marks for correct answer without working

ii (40 x 23.5/1000 =) 0.94 g

1

iii 58 x 0.94/73 (1) = 0.75 g (1)

2 allow 2 marks for correct answer without working allow 0.747 g/0.746 g but not 0.7 g or 0.8 g allow ecf from (i) and (ii) only if working shown

b there is only a small degree of uncertainty (1) all of the titration values are close to average/23.5/all titration values are within 0.1 of average/23.5/titration values have a small range/range of 0.2 (1)

2 ignore references to reliability (for first marking point) allow titration results are reliable

Total 7

51


Question Expected Answers Marks Rationale 6 a i both methods are not sustainable (1)

because feedstock/hydrocarbon/ethene obtained from crude oil which has a finite supply (1)

2

ii old method is less sustainable/ora (1) old method has a by-product/old method has worse atom economy unless uses can be found for the by-product(1)

2 allow named by-product: calcium chloride

b catalyst provides an alternative route for the reaction (1) with a lower activation energy (1)

2 allow reactants stick to catalyst surface (1) increases concentration of reactants (1) allow interaction with catalyst breaks/weakens bonds of reactants (1) allowing products to be formed faster (1) ignore references to collision rate or increased surface area

c 2C2H4 + O2 2(CH2)2O

2

one mark for correct formulae, one mark for balance allow C2H4O for epoxyethane allow displayed formulae if correct balance mark can only be scored if formulae correct subscript numbers must be clearly subscript or no marks

Total 8

Paper Total 55

52

53

Grade Thresholds

General Certificate of Secondary Education Chemistry A (Specification Code J634) June 2009 Examination Series Unit Threshold Marks

Unit Maximum

Mark A* A B C D E F G U

Raw 42 N/A N/A N/A 29 24 20 16 12 0 A321/01

UMS 34 N/A N/A N/A 30 25 20 15 10 0 Raw 42 33 28 23 18 14 12 N/A N/A 0

A321/02 UMS 50 45 40 35 30 25 23 N/A N/A 0 Raw 42 N/A N/A N/A 27 23 19 15 11 0

A322/01 UMS 34 N/A N/A N/A 30 25 20 15 10 0 Raw 42 30 24 19 15 10 7 N/A N/A 0



A323/02 UMS 100 90 80 70 60 50 45 N/A N/A 0 Raw 40 33 30 26 23 19 15 12 9 0

A329 UMS 100 90 80 70 60 50 40 30 20 0 Raw 40 33 31 28 25 21 18 15 12 0

A330 UMS 100 90 80 70 60 50 40 30 20 0

A329/A330 (Coursework) - The grade thresholds have been determined on the basis of the work that was presented for award in June 2009. The threshold marks will not necessarily be the same in subsequent awards. Specification Aggregation Results Overall threshold marks in UMS (ie after conversion of raw marks to uniform marks) Maximum


J634 300 270 240 210 180 150 120 90 60 0 The cumulative percentage of candidates awarded each grade was as follows:

A* A B C D E F G U Total No. of Cands

J634 20.3 47.6 76.0 93.6 98.9 99.8 100.0 100.0 100.0 15121 15456 candidates were entered for aggregation this series For a description of how UMS marks are calculated see: http://www.ocr.org.uk/learners/ums_results.html Statistics are correct at the time of publication.

http://www.ocr.org.uk/learners/ums_results.html

*OCE/V00672*


TWENTY FIRST CENTURY SCIENCE A323/02CHEMISTRY AUnit 3: Ideas in Context plus C7(Higher Tier)

H


• Write your name clearly in capital letters, your Centre Number and Candidate Number in the boxes above.• Use black ink. Pencil may be used for graphs and diagrams only.• Read each question carefully and make sure that you know what you have to do before starting your answer.• Answer all the questions.• Do not write in the bar codes.• Write your answer to each question in the space provided, however additional paper may be used if

necessary.



your answer.


* A 3 2 3 0 2 *


© OCR 2009 [D/103/3792]SP (CW/SW) V00672/5

Candidates answer on the question paperA calculator may be used for this paper



Thursday 4 June 2009Morning


2

© OCR 2009


1 This question is based on the article ‘The bioethanol dilemma’.

(a) Burning bioethanol gives a 70% carbon dioxide reduction compared to petrol.

However, some scientists think that the overall effect of using bioethanol instead of petrol would reduce total carbon dioxide emissions by only about 13%.

Use information from the article to explain why a figure of 13% for overall reduction in carbon dioxide emissions may be more realistic than 70%.

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

(b) It is technically feasible to produce enough bioethanol from crops grown in the UK to satisfy all of our transport needs.

Suggest two disadvantages of this.

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

(c) In the UK it is reasonable to suggest that enough bioethanol can be made from crops to use as a 5% blend with petrol.

It is less reasonable to suggest that developing countries in Africa should do the same.

Explain why.

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

3


(d) The combustion of bioethanol can be represented by this equation.

C2H5OH + 3O2 2CO2 + 3H2O

Octane, C8H18, is one of the hydrocarbons in petrol. The combustion of octane can be represented by this equation.

C8H18 + 12½O2 8CO2 + 9H2O

Burning 1.0 g of bioethanol produces 1.9 g of carbon dioxide.

Burning octane produces about 60% more carbon dioxide than the same mass of bioethanol.

Show that this is true by calculating the mass of carbon dioxide produced when 1.0 g of octane burns, and the percentage increase in carbon dioxide produced compared to bioethanol.

(relative atomic masses: C = 12, H = 1, O = 16)

mass of carbon dioxide = ............................................................ g

percentage increase = .......................................................... [3]

(e) (i) List two factors mentioned in the article that are involved in the Life Cycle Assessment for bioethanol that do not apply to petrol.

1 ........................................................................................................................................

...........................................................................................................................................

2 ........................................................................................................................................

...................................................................................................................................... [2]

(ii) Explain how bioethanol may be a more sustainable fuel than petrol.

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

[Total: 13]

4

© OCR 2009

2 Methanoic acid, HCOOH, is a carboxylic acid that is released in bee stings.

(a) What is the formula of the functional group that is responsible for the characteristic properties of carboxylic acids?

.............................................................................................................................................. [1]

(b) Methanoic acid is used to remove the limescale that can build up in kettles. Limescale is made of calcium carbonate, which is insoluble in water.

Carboxylic acids react with carbonates in a similar way to other acids, such as hydrochloric acid.

calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water

CaCO3 + 2HCl CaCl2 + CO2 + H2O

(i) Complete and balance this symbol equation for the reaction between calcium carbonate and methanoic acid.

....................... + ....................... Ca(HCOO)2 + ....................... + ....................... [2]

(ii) Suggest a property of Ca(HCOO)2 (calcium methanoate) that explains how this reaction removes limescale.

...........................................................................................................................................

...................................................................................................................................... [1]

(iii) Hydrochloric acid is not used to remove limescale from kettles because it is a strong acid.

Methanoic acid is used to remove limescale from kettles because it is a weak acid.

Explain the difference between a strong acid and a weak acid in terms of dynamic equilibrium.


...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

...........................................................................................................................................

.................................................................................................................................. [3+1]

5


(c) Butanoic acid, C4H8O2, is responsible for the unpleasant taste in rancid butter.

Draw a diagram to show the structural formula for butanoic acid.

[1]

[Total: 9]

6

© OCR 2009

3 Vegetable oils are commonly used in cooking. Examples are rape seed oil and sunflower seed oil.

(a) (i) When an ester is hydrolysed it forms an alcohol and a carboxylic acid. This reaction is the reverse of that used to make the ester.

Oils and fats are esters. Write the name of the alcohol and of the type of carboxylic acid to complete this word equation for the hydrolysis of an oil.

oil + water .......................................... + .......................................... [2]

(ii) What two things does the sign tell you about this reaction?

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(b) An ester can be made by reacting an alcohol with a carboxylic acid. The technique used involves four stages: reflux, distillation, purification and drying.

In the reflux stage the alcohol and ester are heated with a little concentrated sulfuric acid in a flask with a condenser attached. The condenser prevents evaporation of the mixture.

In the distillation stage the mixture is heated, and the product collected at its boiling point. This separates the product from most of the impurities.

Describe and explain the other two stages.

purification ..............................................................................................................................

...................................................................................................................................................

drying .......................................................................................................................................

.............................................................................................................................................. [4][Total: 8]

7


BLANK PAGE


8

© OCR 2009

4 A technician carries out an analysis of a mixture of hydrocarbons using gas chromatography.

She first calibrates the equipment using standard hydrocarbons. The retention times for these hydrocarbons are shown in the table.

hydrocarbon retention timein min

methane 1.7

ethane 2.2

propane 3.5

propene 4.0

butane 7.4

The technician then analyses the mixture of hydrocarbons. The recorder print-out from this analysis is shown below.

0

100

0 1.0 2.0 3.0

retention time in min

recorderresponse

4.0 5.0 6.0 7.0 8.0

(a) The mixture contained ethane, propene and butane

(i) Name the hydrocarbon that has the highest concentration in the mixture.

...................................................................................................................................... [1]

(ii) Explain how the recorder print-out shows that this gas has the highest concentration.

...........................................................................................................................................

...................................................................................................................................... [1]

9


(b) Explain how this gas chromatography separated the components of the mixture.

Use ideas about the following in your answer:

• stationary phase • mobile phase • dynamic equilibrium.

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [4]

(c) Two of the hydrocarbons in the mixture are alkanes.

Alkanes burn but they do not react with solutions of other chemicals, for example bromine water.

(i) Explain why alkanes do not react with bromine water.

Use ideas about the bonds in alkanes in your answer.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(ii) The burning of alkanes gives out energy.

Use ideas about bond making and breaking to explain why.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

[Total: 10]

10

© OCR 2009

5 Some indigestion tablets contain the active ingredient, magnesium hydroxide. This neutralises excess stomach acid to relieve the symptoms of acid indigestion. The tablets also contain starch.

A chemist uses quantitative analysis to find the mass of active ingredient in each tablet. He makes a suspension of each of five tablets and titrates these with a solution containing hydrochloric acid. The concentration of this acid is 40.0 g / dm3.

His results are shown in the table.

tablet number 1 2 3 4 5 average

volume ofhydrochloric acid in cm3 23.6 23.5 23.4 23.5 23.5 23.5

(a) Use the average of his results to work out the average mass of magnesium hydroxide in each tablet in the following way.

(i) The relative formula mass of hydrochloric acid is 36.5.

Work out the relative formula mass (RFM) of magnesium hydroxide, Mg(OH)2.


(relative atomic masses: H = 1, Mg = 24, O = 16)

relative formula mass (RFM) of magnesium hydroxide = .......................................................... [2]

(ii) Work out the mass of hydrochloric acid in 23.5 cm3 of the hydrochloric acid solution used in the titrations.

mass of hydrochloric acid = ..................................................... g [1]

11


(iii) Use the neutralization equation below to work out the mass of magnesium hydroxide that reacts with this mass of hydrochloric acid.

Mg(OH)2 + 2HCl MgCl2 + 2H2O

This is the average mass of magnesium hydroxide in each tablet.

mass of magnesium hydroxide in each tablet = ..................................................... g [2]

(b) Use the table of titration results to assess the degree of uncertainty in your calculated value of the mass of magnesium hydroxide in each tablet.

Explain your answer.

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

[Total: 7]

12

© OCR 2009

6 Epoxyethane, (CH2)2O, is an intermediate in the production of car anti-freeze, and is used to sterilize medical supplies.

H H

HH

O

epoxyethane

C C

Epoxyethane is poisonous, carcinogenic and highly flammable.

The raw material used to make epoxyethane is ethene. This is obtained by the cracking of hydrocarbons from petroleum.

Two different methods have been used to make epoxyethane.

In the original method epoxyethane was manufactured in a two stage process.

1 Ethene was passed into an aqueous solution of chlorine.

C2H4 + Cl2 + H2O CH2ClCH2OH + HCl

2 The reaction mixture was treated with calcium hydroxide.

CH2ClCH2OH + HCl + Ca(OH)2 (CH2)2O + CaCl2 + 2H2O

The modern method involves only one step. Ethene and oxygen are passed over a silver catalyst at 250-350 °C.

ethene + oxygen epoxyethane

(a) Compare the sustainability of the two methods in terms of the following:

(i) obtaining the hydrocarbon feedstock used for manufacture,

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

(ii) disposing of the by-products of manufacture.

...........................................................................................................................................

...........................................................................................................................................

...................................................................................................................................... [2]

13

© OCR 2009

(b) The catalyst speeds up the reaction.

Explain how a catalyst carries out this function.

...................................................................................................................................................

...................................................................................................................................................

.............................................................................................................................................. [2]

(c) Write a balanced symbol equation for the reaction that produces epoxyethane in the modern method.

.............................................................................................................................................. [2]

[Total: 8]


14

© OCR 2009

BLANK PAGE


15

© OCR 2009




For queries or further information please contact the Copyright Team, First Floor, 9 Hills Road, Cambridge CB2 1PB.



16

© OCR 2009

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GCSEChemistry A



Mark Scheme for the Units June 2009

J634/MS/R/09

OCR (Oxford Cambridge and RSA) is a leading UK awarding body, providing a wide range of qualifications to meet the needs of pupils of all ages and abilities. OCR qualifications include AS/A Levels, GCSEs, OCR Nationals, Key Skills, Entry Level qualifications, NVQs and vocational qualifications in areas such as IT, business, languages, teaching/training, administration and secretarial skills. It is also responsible for developing new syllabuses to meet national requirements and the needs of students and teachers. OCR is a not-for-profit organisation; any surplus made is invested back into the establishment to help towards the development of qualifications and support which keep pace with the changing needs of today’s society. 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 marks were awarded by Examiners. It does not indicate the details of the discussions which took place at an Examiners’ meeting before marking commenced. 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 should be read in conjunction with the published question papers and the Report on the Examination. OCR will not enter into any discussion or correspondence in connection with this mark scheme. © OCR 2009 Any enquiries about publications should be addressed to: OCR Publications PO Box 5050 Annesley NOTTINGHAM NG15 0DL Telephone: 0870 770 6622 Facsimile: 01223 552610 E-mail: [email protected]

CONTENTS








A323/01 Unit 3 Ideas in Context plus C7 Foundation Tier 42

A323/02 Unit 3 Ideas in Context plus C7 Higher Tier 46

Grade Thresholds 53


1




3. Accept any clear, unambiguous response which is correct, eg mis-spellings if phonetically correct (but check additional guidance).


/ = alternative and acceptable answers for the same marking point (1) = separates marking points not/reject = answers which are not worthy of credit ignore = statements which are irrelevant - applies to neutral answers allow/accept = answers that can be accepted (words) = words which are not essential to gain credit words = underlined words must be present in answer to score a mark ecf = error carried forward AW/owtte = alternative wording ORA = or reverse argument Eg mark scheme shows ‘work done in lifting/(change in) gravitational potential energy’ (1) work done = 0 marks work done lifting = 1 mark change in potential energy = 0 marks gravitational potential energy = 1 mark




7. The list principle: If a list of responses greater than the number requested is given, work through the list from the beginning. Award one mark for each correct response, ignore any neutral response, and deduct one mark for any incorrect response, eg one which has an error of science. If the number of incorrect responses is equal to or greater than the number of correct responses, no marks are awarded. A neutral response is correct but irrelevant to the question.



If there is a set of boxes, some of which should be ticked and others left empty, then judge the entire set of boxes. If there is at least one tick, ignore crosses. If there are no ticks, accept clear, unambiguous indications, eg shading or crosses. Credit should be given for each box correctly ticked. If more boxes are ticked than there are correct answers, then deduct one mark for each additional tick. Candidates cannot score less than zero marks.

Eg If a question requires candidates to identify a city in England, then in the boxes


the second and fourth boxes should have ticks (or other clear indication of choice) and the first and third should be blank (or have indication

of choice crossed out).


2


3



nitrogen monoxide

CO

carbon

monoxide

NO

water vapour SO2

sulfur

dioxide H2O

4

Mark left and right hand sides independently Matching name to formula – two marks for all correct, one mark for two or three correct. (max 2) Matching formula to molecule – two marks for all correct, one mark for two or three correct (max 2) If 2 lines leave or arrive at one box then the mark is lost

b i sulfur dioxide/nitrogen monoxide/SO2/NO

1 either formula must be correct if used

ii carbon monoxide/CO


iii water (vapour)/H2O


Total 7




1

3rd box

b i


1

2nd box

ii



2

4th and 5th boxes

4


Question Expected Answers Marks Rationale 2 c 311;

297 to 322;

2 one mark for each correct answer accept 314/314.5/315 for the mean If 314/314.5/315 is given for the mean then allow 307 to 322 for the range Numbers for a range can be given in either order

d decreases decreases OR increases increases

1

both correct words required – (must be same word used twice)

Total 7

5




1 3rd box

b




3


6



... metal spoon not stained... (1)

... plastic spoon too soft ... (1)

... wooden spoon stained ... (1)

3

2nd, 3rd and 5th boxes

Total 7

7



cotton polyester silk wool

1

correct word circled and no other words circled

b small; long; polymerisation;

3

one mark for each correct choice

c i

carbon (1)

hydrogen (1)

2

1st and 4th boxes

ii food fuels lubricants

1

Total 7

8





2

2nd and 5th boxes

ii calcium carbon chlorine hydrogen neon oxygen sodium

2

all three correct words circled and no others circled for 2 marks two correct words circled for one mark marks are lost if more than three words are circled


toxic ... (1)


2 1st and 5th boxes

9



... safe levels of chemicals ... (1)

1 3rd box

Total 7

10



amino acids amino acids urine urea

4 one mark for each correct choice, correctly placed.

b

body no longer responds to its

own insulin

penicillin injections

type 1 insulin is

destroyed by the pancreas

diet and exercise

type 2 pancreas does

not produce enough insulin

insulin tablets

pancreas

produces too much insulin

insulin injections

2 one mark for each correct ‘row’ linking type of diabetes to both the correct description and the correct treatment More than one line leaving or arriving at a box loses the mark

c anorexia asthma obesity sunburn

1 one mark for the correct word and no other circled

Total 7

11


12



sulfur dioxide SO2

nitrogen monoxide NO

carbon monoxide CO

3

one mark for each correct row do not allow SO2/So2/sO2

do not allow sulfur oxide/sulfur monoxide/sulfur trioxide allow sulfur(IV) oxide do not allow nitrogen oxide/nitrogen dioxide/nitrous oxide allow nitric oxide/nitrogen(II) oxide do not allow No/nO do not allow carbon oxide/carbon dioxide allow carbon(II) oxide do not allow Co/cO

b [1] [3] [2] [2]

3

one mark for each correct number after [1]

Total 6




1

3rd box

b i


1

2nd box

ii



2

4th and 5th boxes

13



... ranges don’t overlap. (1)

... mean before is outside range after ... (1)

2

3rd and 5th boxes

d i A (1)

1 no mark if two or more letters are quoted

ii D (1) 1 no mark if two or more letters are quoted

Total 8

14




1 3rd box

b




3


15



... use and disposal ... (1)

... making the product from the material. (1)

2

2nd and 4th boxes

d

... available locally ...

It is easy to make wooden spoons ...

1

both 1st and 3rd boxes for one mark three or more boxes ticked = 0 marks

Total 7

16


Question Expected Answers Marks Rationale 4 a i B C D

1 one mark for any two of these three correct letters in any order

allow the mark if all three correct letters are given do not allow the mark if incorrect letter A is given

ii A D


iii A D


b

... less plasticizer ... (1)

Increase chain length ... (1)

2

1st and 5th boxes

c

... forces between the molecules.

… forces between the polymer chains stronger.

… but weak forces between …

2

all three of 1st, 4th and 5th boxes for two marks two boxes correct with or without a third incorrect one = one mark four boxes ticked = max one mark ie only gets the mark if all three correct boxes are included five or six boxes ticked = 0 marks

Total 7

17





2 2nd and 5th boxes

ii carbon (1) and hydrogen (1)

2 one mark for each correct word, in either order for three words max 1 mark, for four words no marks for hydrogen allow H or H2 but not h or h2 for carbon allow C but not C2 etc


toxic ... (1)


2 1st and 5th boxes

18



... easier to make ...

... more expensive ...

1 both 1st and 3rd boxes for one mark three or more boxes ticked = 0 marks

Total 7

19


Question Expected Answers Marks Rationale 6 a amino acids

liver urea kidney(s) urine

3 all five words correct for 3 marks four words correct for 2 marks three words correct for 1 mark do not allow monomers for amino acids

b

... pancreas does not produce enough ...

Sugar ... is quickly absorbed ...

... to regulate the amount of sugar ...

2 all three of 2nd, 3rd and 6th boxes for two marks two boxes correct with or without a third one incorrect for one mark four boxes ticked = max one mark ie only gets the mark if all three correct boxes are included five or six boxes ticked = 0 marks

20



the chance ... contracting type 2 ... (1)

the consequences of ... diabetes (1)

2 2nd and 5th boxes

Total 7

21


22



2

all 4 correct = 2 2 or 3 correct = 1

1 correct = 0

Accept other indications of choice (eg lines or crosses)

b i protons (1) neutrons (1)

2

either order

ii 3 electrons arranged 2 inside the inner shell, 1 in the outer shell

1

Total 5

X

X

X


false

true




ii

Do experiments in a fume cupboard. Do not breathe in the gas.


purple

dark grey

iodine gas

solid iodine

23



Iodine solution kills bacteria.


5

24



the colour of the flame


b

a fixed pattern of lines


c

potassium (1) chlorine (1)

2 either order accept any phonetic spellings reject 'chloride'

Total 4

25



4 a 1 If more than 1 box is ticked, 0 marks


2 C and H must be capitals eg Ch4 scores (0) C2h4 scores (1)

allow H4C2/CH2CH2/H2C2H2/H2CCH2

Any number in front of formula, can only score first mark eg

2CH2 scores (1)

2 and 4 must be clearly subscripted or smaller than C and H eg C2H4 or C2H4 scores (1)

Total 3

26



5 a i

more more less

2 all 3 correct = 2 1 or 2 correct = 1 Allow other indications of choice eg underlining

ii

50-65% (1)

1

b 2 all 3 correct = 2 1 or 2 correct = 1 If more than 3 lines are drawn, deduct (1) for each additional incorrect line.

Total 5

good

easily bent

very

property

gold

jewellery

car air

use

27



6 a

Bubbles form around an electrode. The bulb lights up.

2 If more than 2 boxes are ticked, deduct one mark for each additional tick

b ionic (1) ions (1) positive (1)

3

c lead (1)


Total 6

28



7 a i sulfuric (acid)/sulphuric (acid) (1)

1 accept phonetic spelling



b



Total 4

29



8 a

indicator paper


b 3

Total 4

chemical acidic … pH

neutral

8-10

1-2

30



9 a 3

b neutralisation (1)

1 If more than one answer is ringed, deduct (1) for each additional incorrect response. Allow other indications of choice eg underlining

c i 40 (1)

1

ii

She spilled some chemicals.


Total 6

hydrochloric acid (1) burette (1)

flask (1)

31


32



2 all 4 correct = 2 2 or 3 correct = 1 1 correct = 0 Accept other indications of choice (eg lines or crosses)

b Correct symbols: Li and O2(1) Correct balancing: 4Li + O2 (1)

2 Must have capital L and lower case i in Li and capital O with subscripted 2 in O2. Do not allow LI Top of the number 2 in O2 should not be above half the height of the O, Do not allow O2. Second mark can only be scored if formulae are correct. Allow second mark if small errors in formula eg 4Li + O2 scores (1) Allow 4Li + 1 O2

Any other number in front of O2 does not score this mark.

Total 4


falsetrue




ii


purple

dark grey

iodine gas

solid iodine

solid iodine

I2(g)

I2(s)

iodine gas

33



Iodine is in Group 7.

All Group 7 elements kill bacteria.

1 Both must be correct for (1) mark If more than two ticks, 0 marks

Total 5

34



… light of different colours. … very hot and so emit light.


b protons and neutrons named in either order (1)

correct numbers of protons and neutrons: 4 protons, 5 neutrons (1)

4 electrons in arrangement 2,2 (1)

3

Second mark cannot be scored if protons and neutrons not named. 4 neutrons and 5 protons scores first mark only (1) Allow phonetic spelling of protons and neutrons. eg two electrons anywhere in each ‘ring’. Allow other symbols for electrons eg e, - or o

Total 5

X

X

X

X

35


Question Expected Answers Marks Rationale 4 a 1 If more than 1 box is ticked, 0 marks


2 C and H must be capitals eg Ch4 scores (0) C2h4 scores (1) allow H4C2 / CH2CH2 / H2C2H2 / H2CCH2 Any number in front of formula, can only score first mark eg 2CH2 scores (1) 2 and 4 must be clearly subscripted or smaller than C and H eg C2H4 or C2H4 scores (1)

Total 3

36



Potassium iodide is an ionic compound. Ions in the liquid are free to move.


b lead (1)


c e—/e 1 Do not allow word ‘electron’

Total 4

37


Question Expected Answers Marks Rationale 6 a C (1) 1 Allow lower case

More than one letter scores 0

b A (1) 1 As above

c D (1) 1 As above

d

Electrons are shared between atoms. The nucleus of each bonded atom …


e MgF2 (1) 1 Must have capital M and lower case g in Mg and full size F with subscripted 2. Do not allow MGF2/Mg2F/MgF2 /Mg2F /F2Mg Top of the number 2 after F should not be above half the height of the F, Do not allow MgF2. Do not allow if any number is in front of formula eg 2MgF2 scores 0

Total 6

38


Question Expected Answers Marks Rationale 7 a i sulfuric (acid)/sulphuric (acid) (1) 1 accept phonetic spelling



b i

All the acid is used up.


ii

to get more magnesium sulfate …


39


Question Expected Answers Marks Rationale 7 b iii

… largest crystals. …as he heats it. … faster the crystals form. … solid salt evaporate.

2 All 4 correct = 2 2 or 3 correct = 1 1 correct = 0

c



Total 8

true false

40


Question Expected Answers Marks Rationale 8 a i A (1) 1 If more than one choice ringed, 0 marks

ii B and C (1) 1 both needed for the mark If more than two letters ringed, 0 marks

b K+ ringed and both K22+ and K2+ unringed (1)

SO4

2— ringed and both S2- and O2- unringed (1)

2

c

… produces a precipitate. … is a neutralisation reaction. … produces OH— ions. An equation for the reaction is … Hydrogen gas is given off.

3 All 5 correct = 3 4 correct = 2 2 or 3 correct = 1 1 correct = 0

Total 7

true false

41


42

A323/01 Unit 3 Ideas in Context plus C7 Foundation Tier

Question Expected Answers Marks Rationale 1 a i any two from:

corn; maize; sugar (beet);

1 both required for the mark

ii Austria (1) 1

b any two from: produces less carbon dioxide; requires less energy to produce; transport produces less pollution; it is sustainable; it is renewable; it is biodegradable; it is less toxic than fossil fuels; it produces less carbon monoxide/particulate carbon;

2

c i annual wheat surplus of 3.5 million tons would produce enough bioethanol for only about 5%/car engines will have to be modified to use more than 5% bioethanol/insufficient land space to produce the crop/use more wheat than surplus/reduces land space for food (1)

1

ii 20 hectares of wheat (1) 1

d i as more crops are grown for fuel less will be grown for food, causing a shortage (1)

1

ii fossil fuel will be used to produce the fertilizer (1) over use of fertilizer will cause water pollution (1)

2


Question Expected Answers Marks Rationale 1 e i any two from:

(energy used in/environmental impact of:) growing fuel crop/harvesting fuel crop/fuel crop is renewable; fermentation/processing into ethanol; decrease in soil fertility; effect on water supply; use of fertilizers;

2 ignore renewable unqualified

e ii petrol/crude oil is finite/not renewable (1) bioethanol is made from crops, which we can grow more of (1)


Total 13 Question Expected Answers Marks Rationale 2 a circle around COOH group (1) 1

b i methanoic acid + calcium carbonate (1) → calcium methanoate + carbon dioxide + water (1)

2

ii calcium methanoate is soluble (1) 1

iii methanoic acid is a weak acid (1) hydrochloric is a strong acid (1) hydrochloric acid will damage the kettle/methanoic acid will remove limescale without damaging the kettle (1) QWC - at least ten words with no more than one spelling error (1)

4

c structure of CH3 correct (1) structure of COOH correct (1)

2

Total 10

H O H C C H O H

43


Question Expected Answers Marks Rationale 3 a as an energy store (1) 1

b i glycerol (1) + fatty acids (1) 2 either order allow long chain carboxylic acids = fatty acids



c as flavouring/to improve taste (1) to give the required smell/to improve smell (1)

2

Total 7 Question Expected Answers Marks Rationale 4 a time from injection of sample (1)

until chemical leaves column/to appearance of peak/is detected (1)

2 time it takes to go through stationary phase is 2 marks

b i ethane propene butane 2 any order all correct = 2 marks 2 correct 1= 1 mark reject propane

ii propene (1) 1 reject propane

iii propene (1) 1 reject propane

c i any two from: they have unreactive C-C bonds; they have unreactive C-H bonds; they only have single bonds/they do not have double bonds/they are saturated;

2 allow they have unreactive bonds for 1 mark only ignore all their bonds are strong/C-C bonds are stronger than C=C bonds


2 allow as alternative words exothermic = releases energy, endothermic = takes in energy marks can be scored from an annotated energy level diagram

Total 10

44