Fuels

Question 1

what is crude oil

Answer 1

it is a complex mixture of many different kinds of hydrocarbons

Question 2

how do we separate crude oil into simpler, more useful

mixtures

Answer 2

the process of fractional distillation, where each fraction is a simpler mixture than crude oil

Question 3

give 6 fractions which are given of in fractional distillation of crude oil, and their uses

Answer 3

1) gases, used in domestic heating and cooking
2) petrol, used as fuel for cars
3) kerosene, used as fuel for aircraft
4) diesel oil, used as fuel for some cars and trains
5) fuel oil, used as fuel for large ships and in some power
stations
6) bitumen, used to surface roads and roofs

Question 4

describe how hydrocarbons in different fractions differ from each other in the number of carbon and hydrogen atoms their molecules contain

Answer 4

as you go down each fraction, the number of carbon and hydrogen atoms in the molecules increases

Question 5

describe how hydrocarbons in different fractions differ from each other in their boiling points

Answer 5

as you go down each fraction the boiling points increase

Question 6

describe how hydrocarbons in different fractions differ from each other in their ease of ignition

Answer 6

as you go down each fraction it is more difficult to set alight

Question 7

describe how hydrocarbons in different fractions differ from each other in their viscosity

Answer 7

as you down each fraction it becomes more thick and sticky ( higher viscosity).

Question 8

what does the complete combustion of hydrocarbons involve

Answer 8

it involves the oxidation of hydrocarbons.

Question 9

what are the products of the complete combustion of hydrocarbons

Answer 9

carbon dioxide + water

Question 10

what does the complete combustion of hydrocarbons release

Answer 10

it releases energy

Question 11

what happens in incomplete combustion of hydrocarbons

Answer 11

all the hydrogen atoms become oxidised to fomr water, bu the carbon atoms may form:

• some carbon dioxide
• some carbon monoxide
• some soot (solid particle so carbon)

Question 12

give the word equation of incomplete combustion of hydrocarbons

Answer 12

methane + oxygen > carbon dioxide + carbon monoxide + carbon + water

Question 13

explain the problems caused by carbon monoxide

Answer 13

carbon monoxide is a toxic gas. it reduces the amount of oxygen that the blood can carry around the body. breathing in carbon monoxide can kill you

Question 14

explain the problems caused by soot

Answer 14

soot can: build up in chimneys and eventually cause fires, cause lung diseases, make buildings dirty.

Question 15

where does incomplete combustion take place in appliances

Answer 15

in vehicle engines, and faulty gas boilers can produce carbon monoxide and soot.

Question 16

how is sulfur dioxide formed

Answer 16

most hydrocarbon fuels contain impurities such as sulfur. when the hydrocarbons burn, the sulfur is oxidised to form sulfur dioxide

Question 17

how is acid rain formed

Answer 17

acid rain is formed when sulfur dioxide dissolves in water and makes the water acidic

Question 18

what are the effects of acid rain

Answer 18

sulfur dioxide, from power stations and vehicles, dissolves in water in the air. rain becomes more acidic than normal. trees are damaged. rivers, lakes and soils are more acidic, which harms organisms living in them. acid rain speeds up the weathering of buildings and statues.

Question 19

how is the earth warmed

Answer 19

by gases in the atmosphere which trap heat. these gases include carbon dioxide, methane and water vapour.

Question 20

how does the earth’s temperature vary from human activity

Answer 20

the amount of carbon dioxide affects the temperature change in the atmosphere. the amount of carbon dioxide has increased because humans have been burning fossil fuels and so releasing carbon dioxide into the atmosphere. farming also adds methane to the atmosphere.

Question 21

giver two ways in which chemists are trying to control the amount of carbon dioxide in the atmosphere,

Answer 21

1) seeding the oceans with iron compounds. this might encourage microscopic plants to grow, which would use carbon in photosynthesis. this carbon would eventually be included into shells and end up in sediments
2) capturing carbon dioxide from power station waste gas and converting it into hydrocarbons to be used as fuels

Question 22

what are biofuels

Answer 22

fuels obtained from living organisms and can be used instead of fossil fuels.

Question 23

give 1 example of a biofuel

Answer 23

sugar cane/sugar beet, which can be converted to ethanol. this can be used instead of petrol, and reduces the demand for petrol.

Question 24

Evaluate the advantages of replacing fossil fuels with biofuels

Answer 24

1) biofuels are renewable
2) biofuels add less carbon dioxide to the atmosphere than burning fossil fuels, because the plants absorbed carbon dioxide from the atmosphere when they grew.

Question 25

Evaluate the disadvantages of replacing fossil fuels with biofuels

Answer 25

1) growing crops to make into biofuels means that less land is available for growing food. this leads to higher food prices and may lead to some people being short of food.

Question 26

why are most biofuels not carbon neutral

Answer 26

energy is needed to fertilise, harvest and transport the, crops and to make them into a fuel that can be used in vehicles. this energy usually comes from burning fossil fuels, so some carbon dioxide is added to the atmosphere when the biofuels are produced

Question 27

what are the 4 factors of a good fuel

Answer 27

1) should burn easily
2) should not produce ash or smoke
3) should release a lot of heat energy
4) should be easy to store and transport

Question 28

what does a hydrogen fuel cell do

Answer 28

a fuel cell combines hydrogen and oxygen to form water without burning. This reaction releases energy in the form of electricity.

Question 29

evaluate the advantages of using petrol as a fuel

Answer 29

1) burns easily
2) does not produce ash or smoke
3) releases more energy per kg when it burns, than fuels such as such as coal or wood
4) is a liquid, so it is easy to store and transport

Question 30

evaluate the disadvantages of using petrol as a fuel

Answer 30

1) produces carbon dioxide and carbon monoxide as well as water when it burns

Question 31

evaluate the advantages of using hydrogen as a fuel

Answer 31

1) burns easily
2) does not produce ash or smoke
3) only produces water when it burns
4) releases nearly three times as much energy per kg as petrol

Question 32

evaluate the disadvantages of using hydrogen as a fuel

Answer 32

1) is a gas, so it has to be stored at high pressure

2) filling stations would need to be adapted for hydrogen to be used in cars

Question 33

give 4 examples of non-renewable fossil fuels

Answer 33

1) petrol, kerosene and diesel oil. they are all obtained from crude oil.
2) methane is a non-renewable fossil fuel found in natural gas

Question 34

what are alkanes

Answer 34

alkanes are saturated hydrocarbons, which re found in crude oil (natural gas).

Question 35

give 3 example of alkanes

Answer 35

methane, ethane, propane

Question 36

what are alkenes

Answer 36

alkenes are unsaturated hydrocarbons, they have a double bond.

Question 37

give 2 examples of alkenes

Answer 37

ethene, propene

Question 38

describe the bromine water test.

Answer 38

the bromine test is used to find out if a liquid contains double bonds. bromine water is an orange liquid but becomes colourless when mixed with unsaturated molecules

Question 39

what are hydorcarbons

Answer 39

they are compounds that contain hydrogen and carbon