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Question 1

What does the atmosphere + what does it contain?

Answer 1

-the atmosphere (air) that surrounds the Earth is made up of:
78 % nitrogen
21% oxygen
1% argon
plus small amounts of water vapour, carbon dioxide and other gases
-other gases or particulates may be released into the atmosphere by human
activity or by natural processes (e.g. volcanoes), and that these can affect air quality
-the Earth’s early atmosphere was probably formed by volcanic activity and
consisted mainly of carbon dioxide and water vapour

Question 2

What happened to water vapour when the Earth cooled?

Answer 2

water vapour condensed to form the oceans when the Earth cooled

Question 3

What has changed the composition of the atmosphere?

Answer 3

The evolution of photosynthesising organisms added oxygen to, and removed carbon dioxide from, the atmosphere.

Carbon dioxide was removed from the atmosphere by dissolving in the oceans and then forming sedimentary rocks, and by the formation of fossil fuels.

Human activity has changed the composition of the atmosphere by adding:
-small amounts of carbon monoxide, nitrogen oxides and sulfur dioxide to the
atmosphere
-extra carbon dioxide and small particles of solids (e.g. carbon) to the atmosphere

Question 4

What can some of the substances added to the atmosphere by humans do?

Answer 4

• Some of these substances, called pollutants, are directly harmful to humans, carbon monoxide reduces the amount of oxygen that blood can carry
• some are harmful to the environment and so cause harm to humans indirectly, sulfur dioxide causes acid rain

Question 5

What is coal made out of?

Answer 5

Coal is mainly carbon

Question 6

What are fuels made out of?

Answer 6

petrol, diesel fuel and fuel oil are mainly compounds of hydrogen and carbon (hydrocarbons)

Question 7

What is produced when fuels are burnt?

Answer 7

when fuels burn, atoms of carbon and/or hydrogen from the fuel combine with atoms of oxygen from the air to produce carbon dioxide and/or water (hydrogen oxide)

Question 8

what is oxidation + reduction + combustion?

Answer 8

a substance chemically combining with oxygen is an example of oxidation, that loss of oxygen is an example of reduction, and that combustion reactions therefore
involve oxidation

Question 9

What causes fuel to burnt quicker?

Answer 9

Fuels burn more rapidly in pure oxygen than in air

Question 10

What happens during the course of a chemical reaction to conserve mass?

Answer 10

during the course of a chemical reaction the numbers of atoms of each element must be the same in the products as in the reactants, thus conserving mass

Question 11

How is sulfur dioxide is produced?

Answer 11

sulfur dioxide is produced if the fuel that is burned contains any sulfur

Question 12

What happens when fuels are burnt in power stations?

Answer 12

Burning fossil fuels in power stations and for transport pollutes the atmosphere with:
-carbon dioxide and sulfur dioxide
-carbon monoxide and particulate carbon (from incomplete burning)
-nitrogen oxides (from the reaction between atmospheric nitrogen and oxygen at the high
temperatures inside engines)

Question 13

How is nitrogen monoxide formed?

Answer 13

nitrogen monoxide NO is formed during the combustion of fuels in air, and is subsequently oxidised to nitrogen dioxide NO2 (NO and NO2 are jointly referred to as ‘NOx’)

Question 14

What happens to atmospheric pollutants?

Answer 14

atmospheric pollutants cannot just disappear, they have to go somewhere:
-particulate carbon is deposited on surfaces, making them dirty
-sulfur dioxide and nitrogen dioxide react with water and oxygen to produce acid rain
which is harmful to the environment
-carbon dioxide is used by plants in photosynthesis
-carbon dioxide dissolves in rain water and in sea water.

Question 15

How can atmospheric pollution caused by power stations that burn fossil fuels be reduced by?

Answer 15

Atmospheric pollution caused by power stations that burn fossil fuels can be reduced by:

• using less electricity
• removing sulfur from natural gas and fuel oil
• removing sulfur dioxide and particulates from the flue gases emitted by coal-burning power stations

Question 16

How can sulfur dioxide be removed from flue gases?

Answer 16

sulfur dioxide (an acid gas) is removed from flue gases by wet scrubbing:

• using an alkaline slurry e.g. a spray of calcium oxide and water
• using sea water

Question 17

What is the only way to produce less carbon dioxide?

Answer 17

the only way of producing less carbon dioxide is to burn less fossil fuels

Question 18

How can atmospheric pollution caused by exhaust emissions from motor vehicles can
be reduced?

Answer 18

atmospheric pollution caused by exhaust emissions from motor vehicles can be reduced by:

• burning less fuel, for example by having more efficient engines
• using low sulfur fuels
• using catalytic converters (in which nitrogen monoxide is reduced to nitrogen by loss of oxygen, and carbon monoxide is oxidised to carbon dioxide by gain of oxygen)
• adjusting the balance between public and private transport
• having legal limits to exhaust emissions (which are enforced by the use of MOT tests)