AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Crude
oils
andfuels
fuels
Crude
oil and
Hodder Education Revision Lessons
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Overview — crude oil
• Crude oil is derived from an ancient biomass found in rocks.
• Many useful materials can be produced from crude oil.
• Crude oil can be fractionally distilled. Some of the fractions
can be used as fuels.
What useful materials can be made from crude oil?
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Overview — biofuels
• Biofuels are produced from plant material.
• There are advantages and disadvantages to their use as fuels.
• Fuels can come from renewable or non-renewable resources.
What are the advantages and disadvantages of biofuels?
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Crude oil
Crude oil is a mixture of a large number of compounds.
A mixture consists of two or more elements or compounds not
chemically combined together. The chemical properties of each
substance in the mixture are unchanged.
It is possible to separate the substances in a mixture by physical
methods, including distillation.
Why does crude oil have so many different compounds in it?
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Hydrocarbons 1
Most of the compounds in crude oil consist of molecules made
up of hydrogen and carbon atoms only (hydrocarbons).
Most of these are saturated hydrocarbons called alkanes, which
have the general formula CnH2n+2.
What would a model of ethane
(two carbons) look like?
A molecular model of methane and its
structural formula
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Hydrocarbons 2
The many hydrocarbons in crude oil may be separated into
fractions by evaporating the oil and allowing it to condense at a
number of different temperatures.
Each fraction contains molecules with a similar number of
carbon atoms.
This process is called fractional distillation.
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Fractional distillation
Explain how the fractionating column works.
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Properties 1
Some properties of hydrocarbons depend on the size of their
molecules. Look at the table below and on the next slide. What
patterns do you notice?
Carbon atoms
Boiling
Fraction
in the molecule
Description
point (C)
Flammability
Uses
Petroleum
gas
1–4
Colourless gas
Less than 40
Explodes if
mixed with air
and lit
Used as a fuel in
the refinery
Evaporates
Petrol
easily, vapour
mixed with air
is explosive
Used for making
other chemicals
Burns when
heated
Aircraft fuel
Naphtha
5–10
Yellowish liquid,
25–175
flows easily
Kerosene
10–14
Yellowish liquid,
flows like water
150–260
Bottled and sold
as LPG
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Properties 2
Fraction
Carbon atoms
in molecule
Description
Boiling
point (C)
Flammability
Uses
Light gas
oil
14–20
Yellow liquid,
thicker than
water
235–360
Only burns when
soaked onto a wick
or other material
Diesel fuel
Heavy gas
oil
20–50
Yellow brown
liquid
330–380
Only burns when
soaked onto a wick
— very smoky
Used in the
catalytic cracker
Lubricants
(car engine
oils)
50–60
Thick brown
syrup-like liquid
340–575
Only burns when
hot and soaked
onto a wick
Grease for
lubrication
Fuel oil
60–80
Thick brown
sticky liquid
Above 490
Only burns when
hot and soaked
onto a wick
Fuel oil for power
stations and
ships
Bitumen
More than 80
Black semi-solid
Above 580
Only burns if very
hot
Road and roof
surfaces
Catalytic cracker
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Hydrocarbon fuels 1
Most fuels, including coal, contain carbon and/or hydrogen and
may also contain some sulfur.
The gases released into the atmosphere when a fuel burns may
include carbon dioxide, water (vapour), carbon monoxide, sulfur
dioxide and oxides of nitrogen.
Solid particles (particulates) may also be released.
What problems do carbon dioxide, sulfur dioxide and particulates
cause? (Answers on the next slide.)
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Hydrocarbon fuels 2
The combustion of hydrocarbon fuels releases heat.
During combustion, the carbon and hydrogen in the fuels are
oxidised.
• Sulfur dioxide causes acid rain.
• Carbon dioxide causes global warming.
• Solid particles cause global dimming.
How can these effects be reduced? (Answers on the next slide.)
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Hydrocarbon fuels 3
Sulfur can be removed from fuels before they are burned, for
example in vehicles.
Sulfur dioxide can be removed from the waste gases after
combustion, for example in power stations using scrubbers.
Catalytic converters in the exhausts of vehicles reduce the
release of nitrogen oxides.
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AQA GCSE Science & Additional Science
Chemistry 1 Topic 4
Biofuels
What are the issues
with biofuels?
Shariff Che’Lah/Fotolia
Biofuels, including biodiesel
and ethanol, are produced
from plant material, e.g
palm oil. There are
economic, ethical and
environmental issues
surrounding their use.
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