Fuels

Question 1

How is crude oil formed?

Answer 1

1. Sea creatures living millions of years ago
2. Fish die and their bodies fall to the bottom of the ocean
3. Pressure from water pushes them further down and together
4. Fossils of fish turn into crude oil

Question 2

What are hydrocarbons?

Answer 2

Hydrocarbons are molecules that only contain hydrogen and carbon atoms

Question 3

What is crude oil?

Answer 3

Crude oil is a thick, black, viscous liquid that floats on water. It is composed of a very large mixture of hydrocarbons.

Question 4

What is the process of fractional distillation?

Answer 4

Crude oil is heated up until it turns into a gas. The gases enter a fractionating column, and the liquid part, bitumen, is drained off.
The column is hot at the bottom and gets cooler as you go up.
The hydrocarbons in crude oil have different boiling points, so they all condense and drain out at different places.
You end up with the crude oil separated into different fractions.

Question 5

What is the order of the hydrocarbons in crude oil in terms of boiling point and what are their uses?

Answer 5

Gases - heating and cooking
Petrol - motor fuel
Kerosene (paraffin) - jet fuel
Diesel oil - fuel in cars and larger vehicles
Fuel oil - fuel for large ships and some power stations
Bitumen - road and roof surfacing

Question 6

The longer the carbon chain in a hydrocarbon the…

Answer 6

• Higher the boiling point
• Less volatile it is
• More viscous it is
• Less flammable it is

Question 7

What is an alkane?

Answer 7

An alkane is a hydrocarbon with only single carbon bonds. It has the general fomula CnH2n+2. The names of different alkanes all end in -ane. They are saturated, which means there are only single bonds.

Question 8

What does saturated mean?

Answer 8

There are only single bonds, which means they cannot open up and make more bonds.

Question 9

What is the order of alkanes and alkenes?

Answer 9

Methane, ethane, propane, butane, pentane, hexane

N/a, ethene, propene, butene, pentene, hexene

Question 10

What is a homologous series?

Answer 10

A group of chemicals with the same general formula and similar chemical structures and reactions/ chemical properties

Question 11

What is an alkene?

Answer 11

An alkene is a hydrocarbon with a carbon-carbon double bond. It has the general formula CnH2n. The names of different alkenes all end in -ene. They are unsaturated, which means the double bond can open up, allowing the two carbon atoms to bond with other atoms.

Question 12

What is the test for alkenes/ alkanes?

Answer 12

Add bromine water to the alkane or alkene. Bromene water is orange, while alkanes/ alkenes are colourless. Alkanes will not change the colour of the water, while alkenes will make it colourless.

Question 13

How is acid rain formed?

Answer 13

1. Fossil fuels (coal and oil) are burned. Sulphur dioxide is released.
2. In cars nitrogen oxides are formed and released.
3. The gases react with sunlight and ozone and form sulphuric acid and nitric acid.
4. The acids dissolve in the moisture in the atmosphere.
5. They fall down with rain.

Question 14

What are problems of acid rain?

Answer 14

They can contaminate soil by making it too acidic, contaminate water by aluminium, which is activated by acid rain, slow down growth and kill plants and trees and damage buildings.

Question 15

How can we reduce acid rain?

Answer 15

Use less energy
Use more nuclear or renewable energy
Burn coal that contains less sulphur
Construct taller chimneys

Question 16

What are catalytic converters?

Answer 16

Large metal boxes in cars made out of ceramic coated in a metal like platinum or palladium that convert harmful products of incomplete combustion into harmless substances by splitting up molecules. They convert nitrogen oxides into nitrogen and oxygen and carbon monoxide into carbon dioxide, and turn unburned hydrocarbons into carbon dioxide and water.

Question 17

What is complete combustion?

Answer 17

Complete combustion is the burning of an object with lots of oxygen present. It is seen in the blue flame of a gas hob and Bunsen burner. The general formula for the complete combustion of a hydrocarbon is:
Hydrocarbon + oxygen –> carbon dioxide + water

Question 18

What is incomplete combustion?

Answer 18

Combustion that takes place when there is not enough oxygen for complete combustion. It produces less energy than complete combustion. The general formula for the incomplete combustion of a hydrocarbon is:
Hydrocarbon + oxygen –> Carbon monoxide + carbon + water

Question 19

What is cracking?

Answer 19

Cracking is the splitting up of long chain saturated hydrocarbons (alkanes) into smaller unsaturated (alkenes) and alkane molecules.

Question 20

How does cracking happen?

Answer 20

It involves heat (400-700 degrees C), moderate pressure and a catalyst, aluminium oxide. It is an example of thermal decomposition.
The molecules are heated until they turn to vapour and are mixed with a catalyst, which makes them break apart.

Question 21

Why is cracking important?

Answer 21

The supply of different hydrocarbons in crude oil is different to their demand, so you can crack some longer hydrocarbons you have too much of into smaller ones you have too little of in order to match the supply and demand.

Question 22

What is a polymer?

Answer 22

A polymer is a substance of high average relative molecular mass made up of small repeating units called monomers.

Question 23

What is addition polymerisation?

Answer 23

Monomers with a double covalent bond are put under pressure with a catalyst and their double bonds open up and join together to form polymer chains.

Question 24

What are the properties and uses of polyethene/ polythene?

Answer 24

Properties: flexible, electrical insulator, cheap
Uses: Plastic bags, bottles, wire insulation

Question 25

What are the properties and uses of polypropene/ polypropylene?

Answer 25

Properties: Flexible, strong, tough, mouldable
Uses: Crates, furniture, ropes

Question 26

What are the properties and uses of polychloroethene/ PVC?

Answer 26

Properties: Tough, cheap
Uses: Window frames, water pipes

Question 27

What are the properties and uses of polytetrafluroethene/ PTFE/ Teflon?

Answer 27

Properties: Unreactive, tough, non-stick
Uses: Non-stick pans, waterproof clothing

Question 28

What are the advantages and disadvantages of using landfill sites to dispose of polymers?

Answer 28

Advantages: Uses polymers that are difficult to recycle or expensive to separate
Disadvantages: Lots of valuable land is used up. Most polymers are non-biodegradable, which means they are not broken down by microorganisms, so they will sit in landfill for thousands of years.

Question 29

What are the advantages and disadvantages of using combustion to dispose of polymers?

Answer 29

Advantages: Burning plastics produces lots of energy to generate electricity
Disadvantages: Toxic gases can be released. Carbon dioxide is also produced.

Question 30

What are the advantages and disadvantages of using recycling to dispose of polymers?

Answer 30

Advantages: It reduces the amount of waste in landfill sites, reduces emissions of greenhouse and toxic gases, uses less water and energy than making new plastics, saves money and creates jobs and reduces the amount of crude oil we use.
Disadvantages: Polymers have to be separated by type, which can be difficult and expensive, if polymers are mixed together the quality of the final product could be reduced, polymers can only be recycled a finite number of times, melting polymers can release dangerous gases.

Question 31

What are hydrogen fuel cells?

Answer 31

Electrochemical devices like batteries which produce electricity by converting hydrogen and oxygen into water

Question 32

What are the advantages of using hydrogen as fuel?

Answer 32

They do not produce any pollution: the only emission they produce is water vapour
The chemicals in fuel cells are constantly replenished so unlike other batteries, fuel cells will never run flat or need charging

Question 33

What are the disadvantages of using hydrogen as fuel?

Answer 33

The production, storage and distribution of hydrogen for use in fuel cells relies heavily on energy from fossil fuels
Pure hydrogen is expensive and highly flammable

Question 34

What is the name of the reaction between an alkene and bromine water?

Answer 34

An addition reaction