Fuels and Earth Science

Question 1

What is a hydrocarbon?

Answer 1

A compound that contains hydrogen and carbon only

Question 2

What is a crude oil?

Answer 2

• Complex mix of hydrocarbons
• Contains molecules where carbon are in chains or rings
• Important source of useful substances, e.g. fuels and feedstock
• Finite resource

Question 3

How is crude oil separated into useful mixtures?

Answer 3

• Fractional distillation
• Crude oil is heated in the fractionating column and the oil becomes a gas.
• The gas rises through the column which gets cooler further up and condenses at a variety of different temperatures based on the hydrocarbon’s boiling point.

Question 4

Name each fraction and their uses

Answer 4

● Gases: domestic heating and cooking
● Petrol: fuel for cars
● Kerosene: fuel for aircraft
● Diesel oil: fuel for some cars and trains
● Fuel oil: fuel for large ships and in some power stations
● Bitumen: surface roads and roofs

Question 5

How does each fraction differ in properties and why?

Answer 5

• Number of atoms in molecule: increase downwards
• Boiling point: increases downwards
• Ease of ignition: increases upwards
• Viscosity: increases downwards

Physical properties dependent on intermolecular forces that hold chains together, more atoms stronger the force
- Boiling point: more forces of attraction to break in large molecules, high boiling point
- Ease of ignition: Long hydrocarbons have a high boiling point and are hard to ignite
- Viscosity: Stronger forces of attraction between hydrocarbons, harder it is for the liquid to flow

Question 6

What is a homologous series?

Answer 6

A series of compounds which:
- have the same general formula
- similar chemical properties
- have gradual change in physical properties

Question 7

What happens in complete combustion and what kind of reaction is it?

Answer 7

• When carbon dioxide and water is produced
• Exothermic reaction

Question 8

Why does incomplete combustion happen and what gets produced?

Answer 8

Incomplete combustion occurs when there is not enough oxygen around
- produces carbon monoxide and carbon in the form of soot

Question 9

Why is carbon monoxide toxic?

Answer 9

• Combines with haemoglobin so the red blood cells can’t do the proper job of carrying oxygen around the body
• Can lead to fainting, coma and possibly death.

Question 10

What are the issues with incomplete combustion?

Answer 10

• Produces soot which makes buildings look dirty, reducines air quality and can cause or worsen breathing problems
• Carbon monoxide is a toxic gas which can kill

Question 11

How is sulfur dioxide produced?

Answer 11

Most fuels contain some sulfur, and when reacting with oxygen, it produces sulphur dioxide.

Question 12

What issues arise when sulphur dioxide combines with rainwater?

Answer 12

• Causes lakes to become acidic
• Kills trees
• Damages limestone buildings
• Damages stone statues
• Makes metal corrode

Question 13

How are oxides of nitrogen produced?

Answer 13

• When fuels are burnt, nitrogen in the air reacts with oxygen at high temperatures to produce nitrogen oxides.

Question 14

What are the issues with nitrogen oxides?

Answer 14

• Contribute to acid rain
• Cause photochemical smog

Question 15

Advantages and disadvantages of using hydrogen as fuel.

Answer 15

Pros:
- Clean fuel, only produces water in a fuel cell
- Hydrogen obtained from water, so won’t run out. Can even be produced by the water made by the fuel cell
Cons:
- Need expensive engine
- Hydrogen gas needs to be manufactured, uses energy from fossil fuels
- Hard to store

Question 16

What is methane?

Answer 16

non-renewable fossil fuel found in natural gas

Question 17

what is cracking and what conditions are required for it?

Answer 17

• Breaking of large, saturated alkanes into smaller more useful unsaturated alkenes and alkanes.
• Requires heat, moderate pressure and a catalyst.

Question 18

Why is cracking required?

Answer 18

• To help supply and demand, can produce smaller hydrocarbons which are higher in demand.

Question 19

How was earth’s early atmosphere formed?

Answer 19

intense volcanic activity that released gas that formed the early atmosphere

Question 20

What did earth’s early atmosphere contain?

Answer 20

• Little or no oxygen
• A lot of CO2
• Water vapour
• Small amounts of other gases

Question 21

How were oceans formed?

Answer 21

• Water vapour condensed to form the ocean.

Question 22

How did the amount of carbon dioxide in the atmosphere decrease?

Answer 22

• CO2 dissolved into the water

Question 23

How did the volume of oxygen in the atmosphere increase?

Answer 23

• Plants evolved and as they photosynthesised, they removed CO2 and produced O2.
• This led to the amount of O2 in the air building up.

Question 24

What is the chemical test for oxygen?

Answer 24

Put a glowing splint in oxygen and it will relight.

Question 25

How do greenhouse gases work?

Answer 25

• The sun releases short wavelength EM radiation, which passes through the atmosphere.
• The radiation reaches the Earth’s surface and is absorbed and then re-emitted as a IR radiation
• This gets absorbed by greenhouse gases such as CO2, methane and water vapour
• The gases then re-radiate it in all directions, including back to the earth.
• IR radiation is thermal radiation, so this warms up the earth.

Question 26

Why can historical data on temperature less accurate?

Answer 26

• Taken over a small range of places
• Inaccurate equipment

Question 27

What is the composition of todays atmosphere

Answer 27

78% nitrogen
21% oxygen
1% argon
less than 1% other gases

Question 28

Effects of livestock farming on the atmosphere?

Answer 28

• Methane produced by digestive processes of some livestock, so the more livestock farmed, more methane produced.
• Methane is a greenhouse gas.

Question 29

How can the effects of climate change be mitigated

Answer 29

• reduce fossil fuels usage
• encourage public and industry to become more energy efficient