Fuels and the Environment

Question 1

What process is used to separate crude oil into fractions?

Answer 1

Fractional

distillation

Question 2

What property of the different fractions is used to separate them?

Answer 2

Boiling point

Question 3

Briefly outline the main steps used to separate crude oil into fractions

Answer 3

The crude is oil is heated until most of it is vaporised/turned to gas
• It enters the bottom of the fractionating column
• The column is hotter at the bottom and colder at the top
• As the vapours rise, different fractions condense when they reach
their boiling point

Question 4

Name each fraction of crude oil and give a use of each

Answer 4

Gases (cooking
and heating), Petrol (car fuel), kerosene (plane fuel), diesel oil (truck and
train fuel), fuel oil (ship and power station fuel), bitumen (road surfacing)

Question 5

Explain how these properties of the fractions varies as you go from the
bottom of the column to the top

Answer 5

• Carbon chain length decrease
• Boiling point decrease
• Ease of ignition increase
• Viscosity decrease

Question 6

Describe why some compounds can be called hydrocarbons

Answer 6

They contain

hydrogen and carbon only

Question 7

The alkanes are a homologous series of hydrocarbons. Explain why they
are described as being part of the same homologous series.

Answer 7

• Same general formula
• Differ by CH2
• Trend in physical properties
• Similar chemical properties

Question 8

What are the only two products of complete combustion of a

hydrocarbon?

Answer 8

Carbon dioxide and water

Question 9

Write a word equation for the complete combustion of pentane.

Answer 9

Pentane + oxygen —> carbon dioxide + water

Question 10

Write a balanced symbol equation for the complete

combustion of pentane (C5H12)

Answer 10

C5H12 + 8O2 —> 5CO2 + 6H2O

Question 11

When does incomplete combustion occur?

Answer 11

When there is not enough

oxygen for complete combustion

Question 12

What two products (other than carbon dioxide and water) can be formed during incomplete combustion?

Answer 12

Carbon monoxide (CO) and carbon (C)

Question 13

Describe the problems that these products can cause

Answer 13

CO – toxic gas (binds to haemoglobin which stops oxygen binding)
• Carbon – blackens building, causes breathing problems

Question 14

Describe how sulphur impurities in fossil fuels can lead to acid rain.

Answer 14

Sulfur reacts with oxygen to make sulfur dioxide
• Sulfur dioxide dissolves in rain water to form sulfurous acid
• Sulphurous acid is oxidised by oxygen in the air to form sulfuric acid

Question 15

Describe how nitrogen oxides are formed and the problems they can
cause.

Answer 15

Nitrogen and oxygen from the air react in the high temperatures inside
an engine.

Question 16

What is the only product from the combustion of hydrogen?

Answer 16

Water(H2O)

Question 17

Give another advantage of using hydrogen as a fuel

Answer 17

Can be made from renewable resource (water)

Question 18

Give two disadvantages of using hydrogen as a fuel

Answer 18

Difficult to store

A lot of hydrogen is produced using energy from burning of fossil fuels

Question 19

What are the two types of product obtained from cracking?

Answer 19

Alkanes and

alkenes

Question 20

What conditions are needed to crack an alkane?

Answer 20

High temperatures and

pressures, with a catalyst.

Question 21

Explaining why cracking is a useful process.

Answer 21

Matches supply with demand, by cracking low-demand, high supply
longer alkanes into low-supply, high demand shorter alkanes.
Also makes alkenes which are useful for making polymers (plastics)

Question 22

Describe how oxygen and carbon dioxide levels have changed since the
creation of the Earth up to the present day. Explain what caused these
changes.

Answer 22

Carbon dioxide levels started off very high and oxygen very low.
Most of the CO2
dissolved in the oceans. Green plants and bacteria
photosynthesised which reduced CO2
and increased O2.

Question 23

Now describe what happened to water vapour levels.

Answer 23

Water vapour
levels started off high but as the Earth cooled, it condensed into water to
form the oceans.

Question 24

What are the three main greenhouse gases?

Answer 24

Carbon dioxide, methane,

water vapour.

Question 25

Describe how the greenhouse effect occurs, including how greenhouse gases are involved.

Answer 25

The sun emits infrared radiation that is absorbed by the Earth. The Earth cool down and re-emits the radiation (longer wavelength). This is absorbed by greenhouse gases in the atmosphere, which re-emit some of this radiation back towards Earth.

Question 26

Describe and explain the effect that increased greenhouse gas levels are believed to have on the Earth.

Answer 26

More greenhouse gases means more heat | being trapped in the atmosphere, which means higher global temperatures.

Question 27

Give ways in which humans are increasing the levels of carbon dioxide in the atmosphere

Answer 27

Burning fossil fuels. Deforestation.

Question 28

Give ways in which humans are increasing the levels of methane in the atmosphere.

Answer 28

Landfill, paddy fields, livestock farming, melting of | permafrost releasing trapped methane.

Question 29

Explain why temperature and carbon dioxide levels from the past are less precise and therefore less reliable than modern day data.

Answer 29

Temperature readings from hundreds of years ago were from fewer sites and with less precise thermometers. CO2 and temperature readings from hundreds of thousands of years ago are estimates (e.g. tree rings, ice cores, coral rings)

Question 30

Explain whether the graph on page 143 shows a correlation between temperature and CO2 levels.

Answer 30

Yes because the data appears to be linked.

Question 31

Explain whether or not the graph is proof of a causal link between temperature and CO2 levels.

Answer 31

It is not, graphs can never be. Scientific evidence is required to prove a causal link.

Question 32

Describe some effects of climate change.

Answer 32

Increase in extreme weather events (storms, floods, drought). Ice caps melting -> rising sea levels -> flooding. Species going extinct. More wildfires.

Question 33

Give ways that humans can slow down the effects of climate change.

Answer 33

Switch to renewable energy. Insulate homes better. Eat less meat and dairy to reduce livestock farming. Reduce our use of palm oil to reduce deforestation. Plant more trees.