AQA Core Science Unit C1 Revision Guideweb.clhs.mobi/wp-content/uploads/Y11_Revision/SCIENCE/Science...

GCSE Science Electronic Revision Guides

AQA Core Science – Unit C1

Copyright notice: © Beaver Educational Resources and its licensors 2013. All rights reserved.

This material is copyright and must not be shared in any way with other schools e.g. through the use of local authority or school partnership extranets. It must not be posted onto any internet website. This product is for the sole use of the staff and students of:

Cardinal Langley RC High School M24 2GL

Written by Peter Hill, BSc. Clipart from Avanquest Software Publishing and Focus Educational Software Ltd.

CONTENTS PAGE

© Beaver Educational Resources 2013. GCSE Science Electronic Revision Guides Registered to Cardinal Langley RC High School M24 2GL.

Beaver Educational Resources

GCSE Science Electronic Revision Guides

AQA Core Science – Unit C1

Contents (click on a title)

Copyright notice – conditions of use

Topic 1: Atoms and Elements

Topic 1: The Periodic Table

Topic 1: Electronic Structure

Topic 1: Chemical Reactions

Topic 1: Conservation of Mass and Balancing Equations

Topic 2: Using Limestone

Topic 2: Thermal Decomposition of Carbonates

Topic 3: Extracting Metals

Topic 3: Extracting Copper and Recycling Metals

Topic 3: Properties and Uses of Metals

Topic 3 Alloys

Topics 1-3 Questions

Topics 1-3 Answers

Topic 4: Fractional Distillation of Crude Oil

Topic 4: Alkanes and Combustion

Topic 4: Pollution from Burning Fuels

Topic 4: Global Warming and Biofuels

Topic 5: Cracking Hydrocarbons

Topic 5: Polymers

Topic 5: Ethanol

Topics 4 & 5 Questions

Topics 4 & 5 Answers

Topic 6: Vegetable Oils

Topic 6: Saturated and Unsaturated Oils

Topic 6: Emulsions

Topic 7: Plate Tectonics

Topic 7: The Early Atmosphere

Topic 7: The Atmosphere Today

Topics 6 & 7 Questions

Topics 6 & 7 Answers


one electron

The nucleus consists of one proton. The nucleus consists

of six protons and six neutrons.

The inner shell contains two electrons.

The outer shell contains four electrons.

CARBON ATOM

HYDROGEN ATOM

C1 Topic 1: Atoms and Elements

All substances are made of atoms. A substance that is made of only one sort of atom is called

an element. Atoms are the smallest particles of an element that can take part in chemical

reactions. There are about 100 different elements.

Atoms of each element are represented by a chemical symbol e.g. O represents an atom of

oxygen and Na represents an atom of sodium.

Atoms have a small central nucleus which is made up of protons and neutrons and around which

there are shells of electrons. The relative electrical charges are shown in the table below:

Name of particle Charge

Proton +1

Neutron 0

Electron -1

The structures of a hydrogen and carbon atom are shown below:

In an atom, the number of electrons is equal to the number of protons in the nucleus so it has

no overall electrical charge. The electrons move around the nucleus in shells.

The atomic number is the number of protons that an atom contains. All atoms of a particular

element have the same number of protons. Atoms of different elements have different

numbers of protons. The smallest atom is hydrogen with an atomic number of one. Lead is one

of the largest atoms with an atomic number of eighty two.

= positively charged proton

= neutron (no charge)

= negatively charged electron

CONTENTS PAGE


C1 Topic 1: The Periodic Table

All of the elements have been arranged into the periodic table. This contains seven rows of

elements called periods. There are eight columns called groups which contain elements with

similar properties.

Each element is represented by a one or two letter symbol e.g. H represents an atom of

hydrogen and Mg represents an atom of magnesium.

The table also shows the atomic number and mass number for every element. The number of

protons in an atom of an element is its atomic number. The sum of the protons and neutrons in

an atom is its mass number e.g. for the element lithium:

Elements in the same group in the periodic table have the same number of electrons in their

highest energy level (outer shell) and this gives them similar chemical properties.

The elements in Group 0 of the periodic table are called the noble gases. They are unreactive

because their atoms have full outer shells of electrons giving them a stable arrangement.

The atomic mass is 7 because lithium has 3 protons plus 4 neutrons.

The atomic number is 3 because lithium has 3 protons. This also means that lithium has 3 electrons.

7

Li Lithium

3

To find the number of neutrons

in an atom subtract the atomic

number from the atomic mass.

atomic mass

This line divides the metals and the non-metals.

non-metals

most reactive metals

96

MoMolybdenum

42

transition metals

55

MnManganese

25

24

MgMagnesium

12

2

3

4

5

6

7

1

0

I II

1

HHydrogen

1 III IV V VI VII

4

HeHelium

2

7

Li Lithium

3

3

9

BeBeryllium

4

11

BBoron

5

12

CCarbon

6

14

NNitrogen

7

16

OOxygen

8

19

FFluorine

9

20

NeNeon

10

23

NaSodium

11

27

AlAluminium

13

28

SiSilicon

14

31

PPhosphorus

15

32

SSulfur

16

35.5

ClChlorine

17

40

ArArgon

18

39

KPotassium

19

40

CaCalcium

20

45

ScScandium

21

48

TiTitanium

22

56

FeIron

26

59

CoCobalt

27

59

NiNickel

28

63.5

CuCopper

29

65

ZnZinc

30

70

GaGallium

31

73

GeGermanium

32

75

AsArsenic

33

79

SeSelenium

34

80

BrBromine

35

84

KrKrypton

36

85

RbRubidium

37

88

SrStrontium

38

89

YYttrium

39

91

ZrZirconium

40

93

NbNiobium

41

98

TcTechnetium

43

101

RuRuthenium

44

103

RhRhodium

45

106

PdPalladium

46

108

AgSilver

47

112

CdCadmium

48

115

InIndium

49

119

SnTin

50

122

SbAntimony

51

128

TeTellurium

52

127

IIodine

53

131

XeXenon

54

133

CsCaesium

55

137

BaBarium

56

139

LaLanthanum

57

178

HfHafnium

72

181

TaTantalum

73

184

WTungsten

74

186

ReRhenium

75

190

OsOsmium

76

192

IrIridium

77

195

PtPlatinum

78

197

AuGold

79

201

HgMercury

80

204

TlThallium

81

207

PbLead

82

209

BiBismuth

83

209

PoPolonium

84

210

AtAstatine

85

222

RnRadon

86

223

FrFrancium

87

226

RaRadium

88

227

AcActinium

89

magnetic metals

51

VVanadium

23

52

CrChromium

24

Period

Group Group

atomic number

CONTENTS PAGE


C1 Topic 1: Electronic Structure

Electrons occupy particular energy levels called shells around the atom. The shells closest to

the nucleus are at the lowest energy levels. The electrons in an atom occupy the lowest

available energy levels i.e. they fill up the innermost shells first. The first shell can only hold 2

electrons and the second and third shells can hold up to 8 electrons. For example the electronic

structure of the element potassium is shown in the diagram below:

Working out electronic structures

You should be able to represent the electronic structure of the first 20 elements of the

periodic table. The atomic number of an element tells us the number of protons which is equal

to the number of electrons in the shells. The diagram below shows how the shells fill up for the

first 20 elements:

Hydrogen 1

Helium 2 Lithium

2,1 Beryllium

2,2 Boron

2,3 Carbon

2,4 Nitrogen

2,5 Oxygen

2,6 Fluorine

2,7

Neon 2,8 Sodium

2,8,1 Magnesium

2,8,2

Aluminium 2,8,3

Silicon 2,8,4

Phosphorus 2,8,5

Sulfur 2,8,6

Chlorine 2,8,7

Argon 2,8,8 Potassium

2,8,8,1 Calcium 2,8,8,2

Potassium 2,8,8,1

Potassium has an atomic number of 19 therefore it

has 19 electrons in its shells. The shells are filled

from the innermost first. The first 3 shells are

full and the remaining electron occupies a fourth

shell. The number of electrons in the outermost

shell gives the group of the element. Potassiumtherefore belongs in group 1 of the periodic table.

CONTENTS PAGE


A hydrogen atom and a chlorine atom both need one more electron to fill up their outer shells.

Oppositely charged ions are formed which then bond together strongly.

A sodium atom gives its outer electron to a chlorine atom.

C1 Topic 1: Chemical Reactions

When elements react, their atoms join with other atoms to form compounds. This involves

giving, taking or sharing electrons in order to gain full outer shells. This gives the most stable

arrangement of electrons.

Ionic compounds

Compounds formed from metals and non-metals consist of ions. Metal atoms lose electrons to

form positively charged ions. Non-metal atoms gain electrons to form negatively charged ions.

Oppositely charged ions are then strongly attracted to each other and are held together by

ionic bonds. The diagram below shows the formation of a simple ionic compound sodium chloride:

Chemical equations

During chemical reactions atoms are rearranged to make new products with different

properties from the reactants. Chemical reactions can be represented by word equations or by

symbol equations. For example two molecules of hydrogen react with one molecule of oxygen to

form two molecules of water:

hydrogen + oxygen water

2H2(g) O2(g) 2H2O(l)

Cl

Na Cl

Na

Covalent compounds

Compounds formed from non-metals only consist of molecules. In molecules the atoms share

electrons and are held together by covalent bonds. The diagram below shows the formation of

a simple covalent compound hydrogen chloride:

Cl H

Na

Cl H

Na

The two atoms share a pair of electrons (a covalent bond) forming a molecule of hydrogen chloride.

CONTENTS PAGE


A reaction occurs.

C1 Topic 1: Conservation of Mass and Balancing Equations

Atoms are the smallest particles of an element that can take part in chemical reactions. During

chemical reactions atoms are rearranged to make new products with different properties from

the reactants. During chemical reactions atoms are neither created nor destroyed, there is

still the same number of atoms at the end of the reaction as there was at the beginning.

The conservation of mass

The total mass of the products at the end of a reaction is the same as the total mass of the

reactants at the start of the reaction. This rule is called the conservation of mass. If a

reaction takes place in a sealed container there is no change in the total mass of the

container and its contents. This can be demonstrated practically using a precipitation reaction

where two solutions react to form an insoluble precipitate. The mass remains the same:

Balancing equations (H)

In any chemical reaction the number of each type of atom on the left hand side of the equation

(reactants) is equal to the number of each type of atom on the right hand side (products).

Formula equations must be balanced to show this. An equation is balanced by putting numbers

in front of the formulae until the numbers of each type of atom are the same on both sides e.g.

in the reaction between aluminium and oxygen to form aluminium oxide:

Al(s) + O2(g) Al2O3(s)

There are two aluminium atoms on the right hand side but only one on the left hand side and

there are three oxygen atoms on the right but only two on the left. The balanced equation is

shown below:

4Al(s) + 3O2(g) 2Al2O3(s)

State symbols

(s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous (dissolved in water)

Mix calcium chloride and sodium sulfate solutions together.

TOTAL MASS OF FLASK + CONTENTS = 500g

A cloudy white precipitate of calcium sulfate forms.

TOTAL MASS OF FLASK + CONTENTS = 500g

CONTENTS PAGE


C1 Topic 2: Using Limestone

Limestone, chalk and marble are very useful forms of calcium carbonate

(CaCO3) that exist naturally in the Earth’s crust. There is a very high

demand for limestone but there are economic, environmental and social

effects of quarrying it. A balance has to be found between the benefits

and drawbacks of quarrying limestone.

Limestone as a building material

Limestone can be quite easily cut into blocks to make a very useful

building material. It is widely available and is quite cheap compared

to other rocks that are used as building materials. Many old

churches and cathedrals are made of limestone. Statues can also

be carved out of limestone. Limestone is quite hard-wearing but it

can be damaged by acid rain.

Cement and concrete

Cement is made by heating limestone with powdered clay in a kiln.

It can be mixed with sand and water to make mortar which is used

for holding bricks together.

Cement can also be mixed with sand, aggregate (gravel) and water

to make concrete. It can be poured into moulds and reinforced

with steel rods to make building blocks. Concrete is quite a cheap

building material that can be used in the construction of buildings

and bridges.

Drawbacks of quarrying limestone

Quarries are unsightly and can spoil attractive parts of the countryside.

Quarries produce a lot of noise and dirt and can affect the quality of life for local people.

Transport by lorries causes extra noise and dirt in the area.

Quarries destroy the original landscape and the habitats of plants and animals.

Benefits of quarrying limestone

Limestone is a valuable material with many uses.

Chemicals made from limestone can be used to neutralise acidity in lakes and soil which is

caused by acid rain. This helps the environment.

Quarries provide jobs for people in areas where work is often difficult to find. This helps

the local community.

CONTENTS PAGE


,

HEAT

The limewater turns from clear to milky.

C1 Topic 2: Thermal Decomposition of Carbonates

Limestone consists mainly of a chemical called calcium carbonate (CaCO3). When it is heated it

breaks down into calcium oxide (CaO) and carbon dioxide (CO2).

CaCO3(s) CaO(s) + CO2(g)

This process is called thermal decomposition (breaking down with heat).

The carbonates of sodium, magnesium, zinc and copper behave in the same way when heated.

The carbon dioxide gas produced can be tested by bubbling it through limewater. This reacts

with carbon dioxide to produce calcium carbonate which turns it from clear to milky.

METAL CARBONATE METAL OXIDE + CARBON DIOXIDE

Some metal carbonates decompose more easily than others. Less stable metal carbonates

break down more quickly and at lower temperatures. Copper carbonate decomposes at 200°C,

zinc carbonate at 300°C, calcium carbonate at 825°C and sodium carbonate at 1000°C.

The effect of water on calcium oxide

The reaction between calcium oxide and water produces calcium hydroxide. The reaction

produces a lot of heat (exothermic).

CaO(s) + H2O(l) Ca(OH)2(aq)

Calcium hydroxide is an alkali which can be used to neutralise farmers’ soils which have become

too acidic. Powdered calcium oxide can also be used for this purpose but it does not work as

quickly. Calcium oxide is also used to remove acidic gases from the chimneys of coal-fired

power stations, which reduces harmful emissions and helps to reduce acid rain. Calcium

hydroxide is also dissolved in water to produce limewater.

Metal carbonates react with acids to produce carbon dioxide, a salt and water

E.g. zinc carbonate + hydrochloric acid zinc chloride + water + carbon dioxide

ZnCO3(s) + 2HCl(aq) ZnCl2(aq) + H2O(l) + CO2(g)

copper carbonate

clamp

delivery tube

test-tube

bubbles of CO2 gas

CONTENTS PAGE


Potassium

Sodium

Calcium

Magnesium

Aluminium

Zinc

Iron

Tin

Lead

Copper

Extracted by reduction with

carbon in a furnace

Extracted by electrolysis of

molten compounds

LEAST REACTIVE

MOST REACTIVE

C1 Topic 3: Extracting Metals

Most metals exist as chemical compounds (mainly metal oxides) found in rocks called ores.

These metals need to be extracted from their ores. The ore must contain enough metal to

make it economic (not too expensive) to extract. The ores are mined and may be concentrated

before the metal is extracted and purified. A few unreactive metals such as gold and platinum

are found as pure elements because they have never reacted with other elements like oxygen.

Ores require chemical reactions to extract the metal. Metals are extracted either by heating

them with carbon or by electrolysis. Iron is extracted by heating its ore which is mainly iron

oxide with carbon in the form of coke inside a blast furnace. The iron is reduced because

oxygen is removed from it and the carbon is oxidised in the process. The reaction is:

iron oxide + carbon iron + carbon dioxide

2Fe2O3(s) + 3C(s) 4Fe(s) + 3CO2(g)

Aluminium is extracted from its ore (bauxite) which contains aluminium oxide by electrolysis.

The aluminium oxide is melted at a very high temperature and then electrolysis is carried out in

large tanks. During electrolysis positive aluminium ions move towards the negative electrode.

The Reactivity Series

The more reactive a metal is the harder it is to extract from its ore. The method used to

extract a metal depends on its position in the reactivity series:

Electrolysis is a more expensive method of extracting metals than heating with carbon because

large amounts of electricity are used in the process. Therefore more reactive metals cost

more to extract from their ores.

Carbon (non-metal)

CONTENTS PAGE


C1 Topic 3: Extracting Copper and Recycling Metals

Methods of extracting copper

Copper can be extracted from copper-rich ores by heating the ores in a furnace (smelting).

The copper can then be purified to make it a better electrical conductor by using electrolysis.

The supply of copper-rich ores is limited. New ways of extracting copper from low-grade ores

are being researched to limit the environmental impact of traditional mining.

Phytomining uses plants that grow in soils with high levels of copper compounds. The plants

absorb the compounds and then they are harvested and burned. The copper can then be

extracted from the ash that is produced.

Bioleaching uses bacteria to separate copper from copper sulphide. A solution called leachate

is produced that contains the copper which can then be extracted.

Copper can be obtained from solutions of copper salts by electrolysis or by displacement using

scrap iron. Iron is more reactive than copper. A more reactive metal will displace (push out) a

less reactive metal from a solution of its salt. The more reactive metal bonds more strongly to

the non-metal part of the salt which causes the less reactive metal to form as a pure element.

The displacement reaction for iron and copper sulfate solution is:

copper sulfate + iron iron sulfate + copper

Advantages of recycling metals

Mining for metal ores and then extracting the metals from them requires

a lot of energy. Old metal objects can be melted down and converted into

completely new products e.g. drinks cans into parts of a car. The amount

of energy required to recycle metals in this way may only be a small

fraction of the amount needed to extract the metal from its ore.

Environmental and economic benefits of recycling metals include:

It helps to conserve limited reserves of metal ores and fossil fuels

It reduces the need to mine for ores so less damage is done to the landscape

It reduces pollution from mining and burning fossil fuels during extraction processes

It reduces the amount of waste metals so less land is needed for landfill sites

The energy saving makes many recycled metals cheaper.

There are some disadvantages of recycling metals as well. For some metals it can sometimes be

more expensive to recycle them. There are also time and energy costs involved in collecting,

transporting and sorting metals.

CONTENTS PAGE


C1 Topic 3: Properties and Uses of Metals

All metals have the following basic properties in common:

Strong (hard to break)

Shiny when polished

Malleable (can be hammered into shape)

Ductile (can be drawn out into wire)

Conduct heat well

Conduct electricity well

Transition metals

The elements in the central block of the periodic table (shown in red)

are known as transition metals. Like other metals they are good

conductors of heat and electricity and can be hammered into shape.

They are useful as structural materials and for making things that

must allow heat or electricity to pass through them easily.

Different metals have different uses

Different metals have slightly different properties which determine

their uses.

Aluminium has a low density and does not corrode. It is used to make

aeroplanes, trains and some car bodies. Titanium is another low density

metal that does not corrode and is much stronger than aluminium. It is

very expensive and has specialist uses e.g. artificial hip joints, fighter

jet planes and pipes in nuclear power stations.

Copper is a very good conductor of electricity and heat and does not

react with water. It can be bent but is hard enough to be used to

make water pipes and tanks. It also is used to make electric wires and

cables.

Gold is very unreactive so it does not corrode. It is a soft, shiny metal

that is used to make jewellery. Gold is also an excellent conductor of

electricity and is used inside many electronic devices.

Pure iron is too soft to be of much use but it can be converted into an

alloy called steel which is much stronger. Steel has many uses which

include car bodies, bridges, pans, tools and cutlery. Stainless steel

does not corrode and is an alloy of iron and small amounts of chromium

and nickel.

metal transition metal non-metal

CONTENTS PAGE


C1 Topic 3 Alloys

Properties and uses of steels

Most of the iron produced by blast furnaces is converted into alloys called

steels. Various forms of steel are made by adding small amounts of

carbon, chromium or nickel to pure iron. If tiny amounts of carbon are

added to pure iron it results in a soft form of steel which is suitable for

car bodies. If more carbon is added to the iron it results in a harder more

brittle form of steel which is suitable for the blades of cutting tools.

Chromium and nickel can be added to iron to make stainless steel which

does not corrode and is an excellent material for pans, cutlery, taps and

sinks.

Other types of alloys

Most metals in everyday use are alloys. Pure gold is too soft to make

jewellery but it can be hardened by adding metals such as zinc, copper and

silver. Tin can be added to copper to form a much harder alloy called

bronze. Aluminium is strong and light but it is too soft for its many uses

e.g. train and aircraft bodies so it is made harder by alloying it with small

amounts of other similar metals.

Properties of alloys

Other elements can be added to pure metals to form alloys. This often increases the strength

of the product. A model can be used to explain why this happens:

Alloying metals changes their properties and results in new materials which are more suited to

their different uses. Iron from the blast furnace contains about 96% iron and is called cast

iron. The 4% of impurities make it brittle and so it has limited uses. All of the impurities are

removed from most of the iron produced by blast furnaces. Pure iron is easily shaped but it is

too soft for most uses.

Alloying metals changes their properties and results in new materials which are more suited to

their different applications.

Pure metals have regular arrangements of atoms in layers that slide over each other easily if forces are applied to them.

Different elements have different sized atoms. Adding other elements to the metal disrupts the layers making it more difficult for them to slide over each other.

FORCE

CONTENTS PAGE


C1 Topics 1-3 Questions

1. Describe the structure of an atom.

2. What does the atomic number of an element tell you?

3. What does the mass number of an element tell you?

4. What gives elements in the same group of the periodic table similar properties?

5. Sodium has an atomic number of 11. What is its electronic structure?

6. Which group of elements in the periodic table have full outer shells of electrons?

7. Why do elements react to form compounds?

8. What type of compounds form when metals react with non-metals?

9. What happens to electrons when ionic bonds form?

10. What happens to electrons when covalent bonds form?

11. State the law of conservation of mass.

12. Name three forms of calcium carbonate that occur naturally in the Earth’s crust.

13. What makes limestone a very useful building material?

14. How is cement made?

15. How is concrete made?

16. Write a word equation to show what happens to calcium carbonate when it is heated.

17. Describe the chemical test for carbon dioxide gas.

18. Why is heating with carbon not a suitable method for extracting aluminium from its ore?

19. Give two properties of aluminium that make it suitable for making aeroplanes and trains.

20. Give two uses of copper.

21. What is an alloy?

CONTENTS PAGE


C1 Topics 1-3 Answers

1. Atoms have a small central nucleus, which is made up of protons and neutrons and around which

there are shells of electrons.

2. The atomic number of an element tells you the number of protons in the nucleus.

3. The mass number of an element tells you the sum of the protons and neutrons in the nucleus.

4. Elements in the same group of the periodic table have similar properties because they have the

same number of electrons in their highest energy level (outer shell).

5. Sodium has an atomic number of 11 therefore its electronic structure is 2, 8, 1.

6. Group 0 of the periodic table have full outer shells of electrons.

7. When elements react, their atoms join with other atoms to form compounds. This involves giving,

taking or sharing electrons in order to gain full outer shells. This gives the most stable arrangement

of electrons.

8. Ionic compounds form when metals react with non-metals.

9. When ionic bonds form metal atoms lose electrons to form positively charged ions. Non-metal

atoms gain electrons to form negatively charged ions.

10. When covalent bonds form the atoms in the molecule share electrons.

11. The law of conservation of mass states that the total mass of the products at the end of a

reaction is the same as the total mass of the reactants at the start of the reaction.

12. Three forms of calcium carbonate that occur naturally in the Earth’s crust are limestone, chalk

and marble.

13. Limestone is a very useful building material because it can be quite easily cut into blocks, it is

widely available and is quite cheap compared to other rocks that are used.

14. Cement is made by heating limestone with powdered clay in a kiln.

15. Concrete is made by mixing cement with sand, aggregate (gravel) and water.

16. calcium carbonate calcium oxide + carbon dioxide

17. The chemical test for carbon dioxide gas is to bubble it through limewater. This reacts with

carbon dioxide to produce calcium carbonate which turns it from clear to milky.

18. Heating with carbon is not a suitable method for extracting aluminium from its ore because

aluminium is higher than carbon in the reactivity series (it is more reactive than carbon).

19. Two properties of aluminium that make it suitable for making aeroplanes and trains are it has a

low density and it does not corrode.

20. Two uses of copper are to make water pipes and electric wires.

21. An alloy is a metal with other elements added to it to change its properties.

CONTENTS PAGE


LONG CARBON CHAINS

Boiled crude oil vapours enter the tower

350°C

25°C

C1 Topic 4: Fractional Distillation of Crude Oil

Crude oil is a fossil fuel that was formed over millions of years from the dead bodies of tiny

sea creatures which were trapped in sediments at the bottom of seas. They did not decay due

to a lack of oxygen in the sediments. Gradually over time heat and pressure caused them to

turn into oil. Oil is a complex mixture of hydrocarbons. Hydrocarbons are compounds that

contain carbon and hydrogen only.

A mixture consists of two or more elements or compounds not chemically joined together. It is

possible to separate the substances in a mixture by physical methods. Crude oil is separated

into simpler, more useful mixtures by the process of fractional distillation. The oil is boiled

into vapours which are then condensed and separated. This happens inside tall towers or

columns in an oil refinery. A number of simpler mixtures called fractions are produced. Each

fraction contains hydrocarbon molecules of a similar size (similar number of carbon atoms in

them).

The fractions from the top of the tower have short carbon chains so they have low boiling

points, ignite easily and have low viscosity (they are runny).

The fractions from the bottom of the tower have long carbon chains so they have higher

boiling points, are harder to ignite and have high viscosity (they are thick and sticky).

SHORT CARBON CHAINS Gases used in domestic heating and cooking.

Petrol used as fuel for cars.

Kerosine used as fuel for aircraft.

Deisel used as fuel for lorries, some cars and trains.

Fuel oil used as fuel for large ships, some homes and power stations.

Lubricating oil

Bitumen used to surface roads and roofs.

CONTENTS PAGE


Propane: C3H8 Ethane: C2H6 Methane: CH4

C1 Topic 4: Alkanes and Combustion

Most of the hydrocarbons in crude oil are alkanes. They are saturated hydrocarbons because

they have no spare bonds. All of their carbon atoms have four single covalent bonds to four

different atoms. Carbon atoms can form four bonds and hydrogen atoms can only form one

bond. The first three alkanes are methane, ethane, and propane. Their structures are:

The general formula for alkanes is CnH2n+2

Combustion of fuels

A fuel is any substance which can be burnt to release heat energy. Many of the hydrocarbons

from crude oil are used as fuels. Combustion is an example of an oxidation reaction. During

combustion the carbon and hydrogen in the fuels are oxidised. When there is enough oxygen

hydrocarbons burn to produce carbon dioxide and water. This is called complete combustion.

Hydrocarbon + Oxygen Carbon dioxide + Water

E.g. for the complete combustion of methane (natural gas):

CH4(g) + 2O2(g) CO2(g) + 2H2O(l)

Incomplete combustion of hydrocarbons

When there is not enough oxygen hydrocarbons burn to produce carbon and carbon monoxide

as well as carbon dioxide and water. This is called incomplete combustion. It happens because

there is not enough oxygen available to completely oxidise the carbon.

Hydrocarbon + Oxygen Carbon + Carbon monoxide + Carbon dioxide + Water

Less energy is given out in this process. Different percentages of carbon, carbon monoxide and

carbon dioxide are produced depending on the amount of oxygen available. The carbon appears

as tiny black particles (soot) which produces a yellow smoky flame.

Carbon monoxide is a very dangerous toxic gas which is colourless and odourless. It attaches to

the red blood cells which prevents them carrying oxygen around the body. The carbon

monoxide holds on to the red blood cells very strongly and people who have been exposed to

high levels of the gas can suffocate.

CH

HH H C

H

HHC

H

HH C

H

HCH

HH C

H

HH

CONTENTS PAGE


Waste gases can travel many miles in the atmosphere before falling as acid rain.

C1 Topic 4: Pollution from Burning Fuels

Air pollution

Most fuels contain the elements carbon and hydrogen. Coal and oil also contain the element

sulfur which produces sulfur dioxide gas when they are burned.

S(s) + O2(g) SO2(g)

The gases from power stations, homes and car exhausts can cause air to be polluted with sulfur

dioxide and other pollutants including carbon dioxide, water vapour, carbon monoxide and

particulates (solid particles) of soot and unburnt fuels. At high temperatures oxides of

nitrogen may also be released.

Sulfur dioxide dissolves in water vapour in clouds to form dilute sulfuric acid which then falls

as acid rain. Oxides of nitrogen can also form dilute nitric acid. The gases can travel many

miles in the atmosphere from where they were emitted before falling as acid rain.

Problems caused by acid rain

Acid rain has a number of harmful effects on the environment, it:

- acidifies rivers and lakes which kills fish and other organisms

- washes minerals from the soil and releases toxic metals

- damages tree leaves which can eventually lead to the death

of trees and whole forests

- corrodes metal and stonework especially limestone because it

reacts with the calcium carbonate in the stone.

Reducing sulfur dioxide emissions

Governments in many countries have agreed to reduce emissions of sulfur dioxide. This can be

done in the following ways:

removing sulfur from fuels before they are burned

trapping sulfur dioxide gas by fitting scrubbers to the chimneys of power stations

fitting catalytic converters to car exhaust systems

reducing our use of fossil fuels.

CONTENTS PAGE


heat radiation is trapped by gases

atmosphere solar radiation

C1 Topic 4: Global Warming and Biofuels

Greenhouse gases

Various gases in the atmosphere including carbon dioxide, methane and water vapour, trap

heat from the Sun that would otherwise be radiated out into space. This keeps the Earth warm

and it is known as the greenhouse effect.

Changing temperature of the Earth

During the last 200 years humans have increased the concentration of carbon dioxide in the

atmosphere by burning fossil fuels and cutting down forests. Cutting down forests means that

there are fewer trees to remove carbon dioxide by photosynthesis and if they are burnt to

clear land for farming this adds more carbon dioxide to the atmosphere. There is a correlation

(connection) between recent increased carbon dioxide concentrations and global warming and

many scientists believe that humans are causing climate change.

Biofuels

Biofuels are made from plants and animals. Unlike fossil fuels they are renewable (won’t run

out) so they are a good alternative for the future. Biofuels include biodiesel, ethanol, wood,

animal droppings and methane (biogas) from decomposing dung or plant waste.

Advantages of replacing fossil fuels with biofuels

Biofuels are renewable.

Ethanol burns to give just carbon dioxide and water (non-polluting).

Biofuels are carbon neutral so overall it does not add carbon dioxide to the atmosphere.

This is because plants take in carbon dioxide when they are growing which is returned to

the atmosphere when they are burnt.

Disadvantages of replacing fossil fuels with biofuels

Growing the crops to make biofuels requires land and may affect the availability of land

for growing food. It may also lead to forests being cleared to grow biofuel crops.

Energy is needed to make fertiliser for the crops, transport the crops and then process

them into biofuels.

CONTENTS PAGE


water trough

gas jar

short chain alkanes and alkenes collect as gases

delivery tube

HEAT

porcelain chips

mineral wool soaked in paraffin

2

The shorter chain fractions of crude oil e.g. petrol are the most useful. The longer chain

hydrocarbons in some of the fractions such as lubricating oil can be split into shorter chains by

a process called cracking. This involves breaking down large saturated alkane molecules into

smaller more useful alkanes and alkenes which there is more demand for. Cracking is a thermal

decomposition reaction (breaking down with heat). For example the reaction below shows the

products obtained from cracking paraffin which is an alkane containing twelve carbon atoms.

C1 Topic 5: Cracking Hydrocarbons

Octane can be used for petrol and ethene is used to make polymers (plastics).

In industry hot vaporised alkanes are cracked by passing them over heated powdered

aluminium oxide which acts as a catalyst. The vapours can also be cracked by mixing them with

steam and heating them to a very high temperature. The diagram below shows how paraffin can

be cracked in the laboratory.

CH

HCH

HH C

H

HCH

HCH

HCH

HCH

HCH

HCH

HCH

HCH

HCH

HH C

H

HCH

HCH

HHC

H

HCH

HH C

H

HCH

HCH

HC

HH

CHH

+

paraffin (12 C atoms) octane (8 C atoms) ethene (2 C atoms)

The paraffin and porcelain chips are both heated until paraffin vapours pass over the glowing

hot chips. The vapours are cracked as they pass over the porcelain. The shorter chain alkanes

and alkenes are gases. They travel down the delivery tube and collect in the gas jar. The

presence of alkenes can be shown by using them to decolourise orange bromine water.

Alkenes are unsaturated hydrocarbons because they have spare bonds. This is because they

have a carbon-carbon double bond. This is two covalent bonds between two neighbouring carbon

atoms. The first two alkenes are ethene and propene. Their structures are shown below:

Propene: C3H6 Ethene: C2H4

CHH

CHH

CH

CHH

CH

HH The general formula for alkenes is CnH2n

CONTENTS PAGE


Many ethene molecules can combine together.

POLYMERISATION

C1 Topic 5: Polymers

Alkenes are used to make polymers in a process called polymerisation. A polymer contains many

small repeating units called monomers joined together. The name of the polymer indicates

which monomer was used to make it e.g. poly(ethene) or polythene is made by joining many

ethene monomers together. One bond from the double bond of each ethene molecule breaks

and is used to join the ethene molecules together forming a long chain.

The number of ethene molecules that join to make one molecule of poly(ethene) is very large

and it is represented by the letter n. The equation can be written in this shortened form:

Poly(ethene) is flexible and light and has many uses including plastic bags, bottles and insulation

for electrical wires. Other polymers can be made by combining together other monomer

molecules. They all have different properties which make them suited to a range of different

uses e.g. poly(propene) is flexible and tough and is used to make containers such as buckets and

bowls, poly(chloroethene) or PVC is tough and durable and is used for pipes, guttering, window

frames, electric cables and clothing.

New uses are constantly being developed for polymers. Polymer waterproof coatings are used

for fabrics. Dental polymers are used for tooth fillings. Polymer hydrogel wound dressings hold

moisture in the surface of a wound. Smart materials include memory shape polymers e.g.

memory foam mattresses become softer as they warm up and mould to the shape of the person

making them more comfortable. When they cool down they return to their original shape.

CH

HCH

HCH

HCH

HCH

HCH

HCH

HCH

HCH

HCH

HCH

HCH

H

CHH

CHH

CHH

CHH

CHH

CHH

CHH

CHH

CHH

CHH

CHH

CHH

Poly(ethene) is the polymer formed.

n CHH

CHH

n

CH

HCH

H

Problems with plastics

Most plastics are not biodegradable. This means that they do not rot

so when they are thrown away they cause a long-term litter problem.

They will also stay in landfill sites for many years. Scientists are

developing biodegradable plastics to help overcome these waste

disposal problems. Packaging materials and plastic bags are now being

made from polymers and cornstarch so that they break down more

easily. Reusing and recycling plastics also helps to reduce the amount

of waste that humans are producing.

CONTENTS PAGE


C1 Topic 5: Ethanol

Ethanol is a very useful substance that can be used as a solvent and a fuel. Cars can be adapted

to run on a mixture of petrol and ethanol which helps to conserve supplies of crude oil. Ethanol

burns to give just carbon dioxide and water so it is fairly non-polluting.

Production of ethanol from ethene

Hydration is the addition of water to a compound. Ethanol can be produced by the hydration of

ethene. This is done by mixing the ethene with steam in the presence of a catalyst. The

equation for this process is:

ethene (C2H4) + steam (H2O) ethanol (C2H6O)

It may not be possible to continue manufacturing ethanol using this method in the future

because the ethene is obtained from crude oil which is a non-renewable resource.

Production of ethanol by fermentation

Ethanol can also be produced by fermentation of yeast and sugar.

Ethanol produced in this way can be classed as a biofuel because it

is obtained by processing sugar cane, sugar beet or wheat. The sugar

obtained from these plants is used for the fermentation.

The word equation for this process is:

sugar ethanol + carbon dioxide

The ethanol produced in this way is not very concentrated (about 14%) and it must be distilled

to increase its strength.

The advantages of producing ethanol in this way are:

It is renewable.

Using the ethanol as a fuel is carbon neutral so overall it does not add carbon dioxide to

the atmosphere. This is because plants take in carbon dioxide when they are growing

which is returned to the atmosphere when the ethanol is burnt.

The disadvantages of producing ethanol in this way are:

Growing the crops to produce the sugar requires land that could be used for food crops.

Energy is needed to make fertiliser for the crops and to transport and process them.

CATALYST

CONTENTS PAGE


C1 Topics 4 & 5 Questions

1. What are hydrocarbons?

2. How is crude oil separated into simpler, more useful mixtures?

3. Describe what happens to the boiling point and viscosity of crude oil fractions moving from

the top to the bottom of the fractionating tower?

4. How many bonds can carbon atoms form?

5. Why are alkanes described as saturated hydrocarbons?

6. Name the two products that are formed from the complete combustion of a hydrocarbon.

7. Name two other products that are formed if there is not enough oxygen available for the

complete combustion of a hydrocarbon.

8. Explain how carbon monoxide is a very toxic gas.

9. Write a symbol equation to show the formation of sulfur dioxide gas when sulfur burns.

10. What problem does sulfur dioxide cause when it is released into the atmosphere?

11. Give two harmful effects of acid rain.

12. Name two greenhouse gases.

13. Give two ways in which humans have increased the concentration of carbon dioxide in the

atmosphere.

14. What are biofuels?

15. Give two advantages of producing ethanol as a biofuel?

16. Explain what the process of cracking involves.

17. Why are alkenes described as unsaturated hydrocarbons?

18. Name the compound formed by the polymerisation of ethene molecules.

CONTENTS PAGE


C1 Topics 4 & 5 Answers

1. Hydrocarbons are compounds that contain carbon and hydrogen only.

2. Crude oil is separated into simpler, more useful mixtures by the process of fractional distillation.

The oil is boiled into vapours which are then condensed and separated.

3. Moving from the top to the bottom of the fractionating tower the crude oil fractions have longer

carbon chains so they have higher boiling points and higher viscosity (they are thick and sticky).

4. Carbon atoms can form four bonds.

5. Alkanes are described as saturated hydrocarbons because they have no spare bonds.

6. Carbon dioxide and water are the two products that are formed from the complete combustion

of a hydrocarbon.

7. Carbon and carbon monoxide are two other products that are formed if there is not enough

oxygen available for the complete combustion of a hydrocarbon.

8. If carbon monoxide is breathed in it attaches to the red blood cells which prevents them

carrying oxygen around the body. The carbon monoxide holds on to the red blood cells very strongly

and people who have been exposed to high levels of the gas can suffocate.

9. S(s) + O2(g) SO2(g)

10. When sulfur dioxide is released into the atmosphere it dissolves in water vapour in clouds to

form dilute sulfuric acid which then falls as acid rain.

11. Any two harmful effects of acid rain from:

- acidifies rivers and lakes which kills fish and other organisms

- washes minerals from the soil and releases toxic metals

- damages tree leaves which can eventually lead to the death of trees and whole forests

- corrodes metal and stonework especially limestone

12. Any two greenhouse gases from:

- carbon dioxide, methane, water vapour

13. Humans have increased the concentration of carbon dioxide in the atmosphere by burning fossil

fuels and cutting down forests.

14. Biofuels are fuels made from plants and animals.

15. Two advantages of producing ethanol as a biofuel are it is renewable and carbon neutral.

16. Cracking involves breaking down large saturated alkane molecules into smaller more useful

alkanes and alkenes which there is more demand for.

17. Alkenes are described as unsaturated hydrocarbons because they have spare bonds.

18. Poly(ethene) or polythene is the compound formed by the polymerisation of ethene molecules.

CONTENTS PAGE


C1 Topic 6: Vegetable Oils

Extracting vegetable oils

Some fruits, seeds and nuts are rich in oils that can be extracted.

The first stage is to crush the plant material. The oil is then

removed by pressing the crushed plant material between large metal

plates. The oil can be distilled to remove water and impurities.

Vegetable oils as foods

Vegetable oils are important foods. They provide a lot of energy to

the body and we need to be careful not to eat too much of them to

avoid becoming overweight. They also provide us with nutrients.

Vegetable oils are some of the richest sources of vitamin E and they

also provide essential fatty acids which are necessary for good

health.

Biodiesel

Vegetable oils are important fuels for vehicles and they provide a

lot of energy. They are carbon neutral so overall using them does

not add carbon dioxide to the atmosphere. This is because the

plants take in carbon dioxide when they are growing which is

returned to the atmosphere when the oils are burnt. Biodiesel is

similar to ordinary diesel and can be made from rapeseed oil or

waste cooking oil.

Cooking foods

Vegetable oils have higher boiling points than water and so can be

used to cook foods at higher temperatures than by boiling. This

produces quicker cooking and gives foods different flavours.

Cooking foods in oil increases the energy content of the food due to

the oil coating the food. Therefore we must be careful not to eat too

much fried food to avoid becoming overweight.

CONTENTS PAGE


C1 Topic 6: Saturated and Unsaturated Oils

Vegetable oils that are unsaturated contain double carbon-carbon bonds. These can be

detected by reacting with bromine water. Bromine water remains brown if it is shaken with

saturated oils but it decolourises with unsaturated oils. This is because the bromine reacts

with the oil due to the ‘spare’ double bonds.

Hydrogenated oils (H)

Unsaturated vegetable oils have low melting points and are liquids at room

temperature. They can be hardened by reacting them with hydrogen in the

presence of a nickel catalyst at about 60°C. The hydrogen adds to the

carbon-carbon double bonds. This process is called hydrogenation.

The hydrogenated oils have higher melting points so they are solids at room

temperature, making them useful as spreads and in cakes and pastries.

Margarines are made from partially hydrogenated vegetable oils because

this makes them softer than if all of the double bonds were hydrogenated.

Health benefits of eating unsaturated fats

Animal fats in meat and dairy products contain mainly saturated fats while vegetable oils

contain mainly unsaturated fats. It is thought that saturated fats are less healthy to eat than

unsaturated fats as they increase the cholesterol levels in the blood. People with high

cholesterol levels are more at risk of developing heart disease. Therefore eating mainly

unsaturated fats can lower the risk of heart disease.

bromine water

shake with unsaturated oil

bromine water decolourises

CHH

CHH

CH

HHC

H

HHH2 +

nickel catalyst

60°C

CONTENTS PAGE


oil

water droplets cannot join together and separate out

hydrophobic tail

emulsifier molecule

C1 Topic 6: Emulsions

Oils do not dissolve in water. They can be mixed and shaken with water to produce emulsions.

An emulsion consists of droplets of one liquid suspended in another liquid. Droplets of oil can be

suspended in water or droplets of water can be suspended in oil.

How emulsifiers work (H)

Emulsifiers have special molecules. One end of the molecule is hydrophilic (water-loving) and

the other end is hydrophobic (water-hating). The hydrophilic part is attracted to water and the

hydrophobic part is attracted to oil. The molecules arrange themselves so that they surround

water or oil droplets. The droplets are repelled from each other and so will not separate out.

hydrophilic head

Emulsions are thicker than oil or water and have many uses that depend on their special

properties. They provide better texture, coating ability and appearance, for example in

mayonnaise, salad dressings, ice creams, cosmetics and paints.

Mayonnaise is an emulsion of tiny droplets of vinegar in oil. Normally the droplets of vinegar

would slowly join back together and form a separate layer to the oil but an emulsifier is added

to the mayonnaise to stop this happening. Emulsifiers are chemicals that make emulsions more

stable.

oil

emulsion of oil in water e.g. cream emulsion of water in oil e.g. butter

water

water droplet oil droplet

CONTENTS PAGE


The Earth is made up of several layers:

- The crust is a thin outer layer of solid rock surrounded

by the atmosphere.

- The mantle is a mixture of solid and molten rock which

can flow very slowly. Radioactive decay produces heat

which causes convection currents in the mantle.

- The outer core is a very hot, dense liquid layer

composed mainly of iron and nickel.

- The inner core is a very hot, dense solid layer composed

mainly of iron.

liquid outer core

solid inner core

mantle

C1 Topic 7: Plate Tectonics

Tectonic plates

The Earth’s crust is broken up into a number of sections called tectonic plates which float on

the mantle. The tectonic plates move very slowly (a few centimetres per year) due to

convection currents in the mantle. This movement is known as continental drift.

At plate boundaries (where they meet) the plates may slide past each other. Friction between

plates may prevent them from moving past each other at first. Forces gradually build up until

they are big enough to overcome the friction between the plates and then they move with a

sudden jerk which causes an earthquake to occur. Earthquakes and volcanoes often occur at

plate boundaries.

Scientists find it difficult to predict when earthquakes and volcanic eruptions will occur

because the fault lines are often deep within the Earth’s crust and they cannot measure the

forces between the tectonic plates. The scientists do not know when these forces will be great

enough to cause sudden movements.

Wegener’s theory of continental drift

Scientists once thought that the mountains and valleys on the Earth’s surface were the result

of the shrinking of the crust as the Earth cooled down following its formation. Alfred Wegener

first proposed the theory of continental drift in 1915. He noticed that the shapes of the

coastlines of Africa and South America seemed to fit like pieces of a jigsaw so perhaps they

had been joined together as one land mass in the distant past. He also used evidence from

fossils found in both of these regions which were from the same species of extinct reptile.

Matching layers of rocks in different continents and fossils of tropical plants in arctic regions

provided additional evidence for his theory. At first Wegener’s theory was not accepted by

other scientists but this changed over time as more evidence was found to support it.

crust

CONTENTS PAGE


CO2 dissolves into oceans

Water vapour condensed to form oceans.

cooling over time

Volcanoes gave out CO2 and water vapour.

C1 Topic 7: The Early Atmosphere

For the past 200 million years, the proportions of different gases in the atmosphere have been

much the same as they are today, but when the Earth was first formed its surface was molten

and there was no atmosphere. As the Earth cooled down a thin crust formed and during the

first billion years of the Earth’s existence there was a large amount of volcanic activity. The

early atmosphere was then formed from gases produced by erupting volcanoes. There are

several theories about how the atmosphere was formed. One theory suggests that during this

period it consisted mainly of carbon dioxide and there was little or no oxygen. There may also

have been water vapour and small proportions of methane and ammonia.

As the Earth continued to cool the water vapour condensed to form oceans. Scientists think

that about half of the carbon dioxide in the atmosphere gradually dissolved into the oceans

over time. This dissolved carbon dioxide was then incorporated into the shells of marine

organisms which eventually died and formed sediments. Over millions of years the carbon

dioxide became ‘locked up’ as these sediments formed carbonate rocks.

Green plants and oxygen

Life on Earth began billions of years ago and there are many theories as to how the first simple

organisms formed. Scientists think that about one billion years ago primitive green plants and

algae started to evolve. Photosynthesis converted carbon dioxide into oxygen and so over time

the concentration of oxygen in the atmosphere gradually increased while the concentration of

carbon dioxide decreased.

How life on Earth was formed (H)

There are many theories as to how life on Earth was formed. The ‘primordial soup’ theory

involves the interaction between methane, ammonia, hydrogen and lightning in the early

atmosphere. It is thought that lightening could have caused a chemical reaction between these

gases which resulted in the formation of amino acids, the building blocks for proteins. The

amino acids could then have combined to form organic matter in the primitive oceans (the

primordial soup). In 1952 Miller and Urey carried out an experiment to test this theory. They

sealed a mixture of these gases together with water inside a flask. The mixture was heated to

produce water vapour and electric sparks were passed through it to simulate lightning. After a

week amino acids were found to have formed which provided evidence to support this theory.

CO2 ‘locked up’ in rocks formed from calcium carbonate shells.

CONTENTS PAGE


oxygen and argon

liquified air

nitrogen

Today’s atmosphere has the following composition of gases:

- Nitrogen (N2) 78%

- Oxygen (O2) 21%

- Argon (Ar) 0.9%

- Carbon dioxide (CO2) 0.04%

There are traces (tiny amounts) of other gases as well. The amount of water vapour in the

atmosphere varies greatly.

Increasing levels of carbon dioxide in today’s atmosphere

Carbon dioxide is released into the atmosphere when coal, oil or gas is burnt. Humans are

increasing the amount of carbon dioxide in the atmosphere and many scientists believe that

this is causing global warming through the greenhouse effect. Humans have also cleared vast

areas of natural forest for timber and to create more farm land. This means that there are

fewer trees to remove carbon dioxide from the atmosphere by photosynthesis. This may also

be causing global warming.

The oceans act as a natural reservoir for carbon dioxide by absorbing it from the atmosphere, but the extra carbon dioxide is making them too acidic. This is harming the natural ecosystems

of the oceans.

Investigating the proportion of oxygen in the atmosphere

The proportion of oxygen in the atmosphere can be measured using the apparatus below:

100 cm3 air

HEAT

copper wire

C1 Topic 7: The Atmosphere Today

Fractional distillation of air (H)

Air is a mixture of gases with different boiling points and can be

fractionally distilled to provide a source of raw materials used in a

variety of industrial processes. The air is first filtered and then

cooled to about -200°C. Frozen carbon dioxide is removed and then

the liquified air is heated slowly inside a fractionating column to

separate the gases by fractional distillation. Oxygen and argon

come out together and are then separated in a second column.

100 cm3 of air is passed backwards and forwards over the heated copper wire. The volume of

air reduces as the copper reacts with the oxygen in the air to form black copper oxide. An

excess of copper is used to ensure that all of the oxygen reacts. Eventually the volume of air

inside the syringes stays steady at 79 cm3 showing that 21% of the air was oxygen.

CONTENTS PAGE


C1 Topics 6 & 7 Questions

1. Vegetable oils are said to be carbon neutral fuels. What does this mean?

2. Vegetable oils have higher boiling points than water. How is this an advantage in cooking?

3. Describe the chemical test that can be used to detect double carbon-carbon bonds in

unsaturated vegetable oils.

4. Describe how unsaturated vegetable oils can be hardened. (Higher paper)

5. What is the possible health benefit of eating unsaturated fats instead of saturated fats?

6. What does an emulsion consist of?

7. What are emulsifiers?

8. Name the four layers that make up the Earth.

9. Name two major events that often occur at tectonic plate boundaries (where plates meet).

10. How do scientists think the Earth’s early atmosphere was formed?

11. Which gas in the Earth’s early atmosphere gradually became ‘locked up’ in carbonate rocks?

12. In the ‘primordial soup’ theory which important compounds are thought to have been

formed from various gases in the early atmosphere? (Higher paper)

13. Name the two gases which make up 99% of the atmosphere today.

14. Which gas is released into the atmosphere when fossil fuels are burnt?

15. What problem is the extra carbon dioxide causing in the oceans?

16. How can the gases in air be separated and collected to provide a source of raw

materials for industry. (Higher paper)

CONTENTS PAGE


C1 Topics 6 & 7 Answers

1. Vegetable oils are said to be carbon neutral fuels so overall using them does not add carbon

dioxide to the atmosphere. This is because the plants take in carbon dioxide when they are growing

which is returned to the atmosphere when the oils are burnt.

2. Vegetable oils have higher boiling points than water so they can be used to cook foods at higher

temperatures than by boiling. This produces quicker cooking and gives foods different flavours.

3. Vegetable oils that are unsaturated contain double carbon-carbon bonds. These can be detected

by reacting with bromine water. Bromine water remains brown if it is shaken with saturated oils but

it decolourises with unsaturated oils.

4. Unsaturated vegetable oils can be hardened by reacting them with hydrogen in the

presence of a nickel catalyst at about 60°C. The hydrogen adds to the carbon-carbon double

bonds. This process is called hydrogenation. (Higher paper)

5. It is thought that saturated fats are less healthy to eat than unsaturated fats as they increase

the cholesterol levels in the blood. People with high cholesterol levels are more at risk of developing

heart disease. Therefore eating mainly unsaturated fats can lower the risk of heart disease.

6. An emulsion consists of droplets of one liquid suspended in another liquid. Droplets of oil can be

suspended in water or droplets of water can be suspended in oil.

7. Emulsifiers are chemicals that make emulsions more stable.

8. The four layers that make up the Earth are the crust, mantle, liquid outer core and solid inner

core.

9. Earthquakes and volcanoes often occur at tectonic plate boundaries.

10. Scientists think that the Earth’s early atmosphere was formed from gases produced by erupting

volcanoes.

11. Carbon dioxide gas in the Earth’s early atmosphere gradually became ‘locked up’ in carbonate

rocks.

12. In the ‘primordial soup’ theory amino acids are thought to have been formed from various

gases in the early atmosphere? (Higher paper)

13. Nitrogen (78%) and oxygen (21%) are the two gases which make up 99% of the atmosphere

today.

14. Carbon dioxide is released into the atmosphere when fossil fuels are burnt?

15. The oceans act as a natural reservoir for carbon dioxide by absorbing it from the atmosphere

but the extra carbon dioxide is making them too acidic. This is harming the natural ecosystems of

the oceans.

16. The gases in air can be separated and collected by fractional distillation to provide a

source of raw materials for industry. (Higher paper)

CONTENTS PAGE


AQA Core Science Unit C1 Revision Guideweb.clhs.mobi/wp-content/uploads/Y11_Revision/SCIENCE/Science...

Documents

Transcript of AQA Core Science Unit C1 Revision Guideweb.clhs.mobi/wp-content/uploads/Y11_Revision/SCIENCE/Science...