Topic 5 – Fuels – Q and A
Topic 5 – Fuels
Credit
1 Fractional distillation produces
hydrocarbons with varying
numbers of carbon atoms in the
different fractions.
How does increasing the numbers
of carbon atoms in the molecules
affect:
a) boiling point
b) flammability
c) viscosity
Boiling point increases
Get less flammable
Get stickier
2 A compound produces carbon
dioxide and water when it is
burned in a plentiful supply of air.
a) What elements must be present
in the compound?
b) Justify your answer to (a)
above.
Carbon and hydrogen
Carbon can give carbon dioxide when
burned.
Hydrogen can give water when burned.
(Note oxygen could come from air)
3 a) What metals are used as
catalysts in catalytic converters?
b) What does the catalytic
converter do to harmful gases?
c) Complete the word equation for
the reaction in a catalytic
converter:
carbon monoxide + nitrogen
oxide

____ + _____
a) Platinum and rhodium
b) Converts them to less harmful gases.
c) Carbon dioxide + nitrogen
4 Car exhausts sometimes release
unburnt petrol and at other times
release carbon monoxide when
petrol is not burned fully.
What measure can be taken to
increase the efficiency of
combustion of petrol and so reduce
these forms of pollution.
Increase the air to fuel ratio. This
ensures that petrol is burnt more
efficiently.
1
Topic 5 – Fuels – Q and A
1
What is a fuel?
A substance that burns to give energy
2
What is meant by combustion?
Burning in oxygen.
3
Give the test for oxygen.
Relights a glowing splint.
4
What are the percentages
(approx) of nitrogen and
oxygen in the air?
Oxygen – 20%
Nitrogen – 80%
5
What is meant by an
exothermic reaction?
A reaction which gives out heat (eg
burning)
6
What is meant by a fossil fuel?
A fuel formed from ancient remains.
7
Explain how coal was formed
(4 x ).
Ancient plants died.
Covered with mud and rock
Changed by heat and pressure over
mllions of years.
8
Why are fossil fuels called
finite resources and why is this
a problem?
There is only a fixed amount. One day
they will run out.
9
What 2 pollution problems are
caused by burning oil/coal?
Acid rain (from sulphur dioxide).
Greenhouse effect (carbon dioxide)
10
What pollution problem is
caused by transporting oil?
Spillages of oil kill sea life.
11
What pollution problem is
caused by coal mining?
The landscape is ruined.
12
Complete the word equations:
a) carbon + oxygen -->
carbon dioxide
b) methane (CH4) + oxygen
carbon dioxide + water
13
What type of chemicals make
up crude oil?
Hydrocarbons
14
What can you say about the
melting points and the boiling
points of the substances that
make up crude oil?
There is a range of different melting
and boiling points.
15
What is meant by a fraction
with regard to crude oil?
A group of substances with boiling
points in a given range (eg petrol
fraction)
2
Topic 5 – Fuels – Q and A
16
Name the process used to
separate crude oil into useful
fractions?
Fractional distillation
17
What does viscosity mean?
Stickiness (thickness)
18
As the boiling points of the
fractions increase, how are the
following affected:
a) ease of evaporation b) flammability
c) viscosity
a) evaporation gets harder
b) flammability gets less
c) viscosity gets more (stickier)
19
What is the definition of a
hydrocarbon?
A compound of hydrogen and carbon
only.
20
Give the test for carbon
dioxide.
Turns lime-water milky.
21
Give the test for water.
Boils 100oC and freezes 0oC
22
What are the only 2 products
when hydrocarbons burn
completely?
Carbon dioxide and water
23
Name a poisonous gas
produced by the burning of
fossil fuels.
sulphur dioxide
Carbon monoxide (incomplete
combustion)
24
What compounds could be
removed from fossil fuels to
reduce the amount of this gas
released into the air?
Remove all sulphur
(desulphurisation)
25
Why are nitrogen oxides
produced inside a car engine?
Because nitrogen and oxygen from the
air get sparked and react.
26
Why is lead no longer used as
an additive to petrol?
Lead is a poison and is released from
exhausts damaging the environment.
27
Give 2 ways air pollution from
car engines can be reduced.
Lead free petrol.
Catalytic converter.
Lean burn engine.
3