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Air Quality
(OCR 21st Century)
W Richards
The Weald School

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Section C1.1 – Our air

3. The Earth’s Atmosphere
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Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2
Carbon dioxide, water vapour
Oxygen
Nitrogen
Noble gases

4. Air
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Air is a mixture of different gases consisting of small molecules with large spaces between them:

5. Evolution of the Earth’s Atmosphere
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Carbon
dioxide
Methane
Ammonia
Oxygen
Nitrogen
Others
Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2
4 Billion years
3 Billion years
2 Billion years
1 Billion years
Present day

6. Evolution of the Earth’s Atmosphere
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Volcanic activity releases CO2, methane, ammonia and water vapour into the atmosphere. The water vapour condenses to form oceans.
Some of the oxygen is converted into ozone. The ozone layer blocks out harmful ultra-violet rays which allows for the development of new life.
4 Billion years
3 Billion years
2 Billion years
1 Billion years
Present day
Green plants evolve which take in CO2 and give out oxygen. Carbon from CO2 becomes locked up in sedimentary rocks as carbonates and fossil fuels. Methane and ammonia react with the oxygen and nitrogen is released.

7. Carbon dioxide in the atmosphere
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The amount of CO2 in the atmosphere is affected by 3 things:
1) Geological activity moves carbonate rocks deep into the Earth and they release ______ _______ into the atmosphere during volcanic activity.
2) When fossil fuels are burned the carbon contained in them reacts with _____ to form CO2.
3) Increased CO2 in the atmosphere causes a reaction between it and _______. These reactions do not remove ALL of the new CO2 so the greenhouse effect is still getting _______!
Words – oxygen, seawater, carbon dioxide, worse

8. Pollution What happens to pollution?
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What happens to pollution?
Carbon dioxide causes global warming but some of it can be removed by plants (photosynthesis) or reactions with seawater.
Sulfur dioxide and nitrogen dioxide cause acid rain which damages trees and buildings.
Particulates (like in smog) can make buildings dirty and worsen breathing difficulties.

9. Pollution Humans pollute the Earth in a number of ways: Pollutant
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Humans pollute the Earth in a number of ways:
Pollutant
Harmful to...
Why?
Carbon dioxide
Environment
Nitrogen oxides
Environment + humans
Sulfur dioxide
Particulates (e.g. Smoke)
Carbon monoxide
Humans
A greenhouse gas that causes global warming
Causes acid rain and makes asthma/breathing problems worse
Causes acid rain
Makes buildings dirty and makes asthma worse
Displaces oxygen in red blood cells that can result in death

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Section C1.2 – Pollution

11. Fuels
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Fuels are substances that can be used to release useful amounts of energy when they burn, e.g.
Wood
Gas
Oil
Coal
These fuels are called “fossil fuels” and are described as being “non-renewable”. The main element in these fuels is Carbon.

12. Burning Hydrocarbons
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Oil, petrol and diesel are all examples of HYDROCARBONS. A hydrocarbon is a compound made up of carbon and hydrogen.
Burning hydrocarbons will produce water, carbon dioxide and energy: C H O O H C O
Methane
Oxygen +
Carbon dioxide
Water +
In this reaction the hydrocarbon is “oxidised” (“oxidised” means that oxygen has been added and it’s the opposite of reduced).

13. More information on oxygen
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Fuels need oxygen to burn. The more oxygen they have, the quicker they will burn. This is the principle behind oxy-acetylene torches:

14. Other products of burning fuels
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Sulphur dioxide
Sulphur dioxide: S O
Sulphur
Oxygen +
Nitrogen monoxide N O
Oxygen + O
Nitrogen N
Nitrogen monoxide:
Nitrogen monoxide can be further oxidised to make nitrogen dioxide (Nitrogen monoxide and dioxide are jointly referred to as NOx): O
Oxygen +
Nitrogen monoxide N
Nitrogen dioxide N O

15. Conservation of mass in reactions
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In any reaction the total mass of products is the same as the total mass of the reactants
Example 1 – Magnesium oxide and hydrochloric acid Mg O H Cl
1 x magnesium, 1 x oxygen, 2 x hydrogen and 2 x chlorine atoms
Also 1 x magnesium, 1 x oxygen, 2 x hydrogen and 2 x chlorine atoms
Example 2 – Burning methane C H O

16. Incomplete Combustion
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As well as producing carbon monoxide, incomplete combustion can also produce soot:
Little oxygen: C H
Methane O
Oxygen +
Water
Carbon
“Soot”

17. Burning Fossil Fuels
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Burning fossil fuels like oil and coal causes pollution.
Oil contains carbon: C H O
Carbon dioxide is a “greenhouse gas” – it helps cause global warming
Coal contains carbon, sulfur and other particles:
sulfur + oxygen sulfur dioxide
Sulfur dioxide causes acid rain. Other particles can cause “global dimming” – sunlight is absorbed by the particles in the atmosphere.

18. Summary of pollutants
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Each of the following chemicals is a product of burning fossil fuels. For each one summarise how it is made and what harm it causes: C O
Carbon dioxide
Nitrogen monoxide N O C
Carbon monoxide O O H
Water S O
Sulfur dioxide C
Carbon
Nitrogen dioxide O N

19. C1.3 Improving Air Quality
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C1.3 Improving Air Quality

20. Removing Pollution There are many ways pollution can be reduced:
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There are many ways pollution can be reduced:
Use less electricity/central heating
Remove toxic chemicals before or after they are burnt
Use alternative energy sources, e.g. wind power

21. Removing Sulfur
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Sulfur dioxide is clearly bad for the environment so it’s a good idea to remove as much sulfur as possible:
Vehicles can remove sulfur from fuels before they are burned.
Power stations can remove sulfur dioxide from waste gases after combustion.

22. Wet Scrubbing
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“Wet scrubbing” is a term used to describe the removal of sulfur dioxide and other particles using seawater or an alkaline spray:
Step 1 – the dirty gas is fed in through the top.
Step 3 – the mixture is fed into a cyclone area where the slurry is collected at the bottom of the device.
Step 2 – the “scrubbing liquid” (seawater or alkaline spray) is fed in through the side.

23. Reducing Pollution from vehicles
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A number of suggestions:
1) Buy a new, smaller, more efficient car
2) Use legal limits (e.g. An MOT) to enforce lower emissions
3) Use low sulfur fuels or convert your car to run on biodiesel
4) Make sure your car has a catalytic converter:
Carbon monoxide + oxygen carbon dioxide
Nitrogen monoxide + carbon monoxide nitrogen + carbon monoxide
5) Use the train or a bus!

24. Alternative Fuels
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Car makers are currently researching two alternatives for petrol and diesel-powered cars. What are the advantages and disadvantages of each?
Electric cars
Advantages:
Disadvantages:
Biofuel cars
Advantages:
Disadvantages:

25. Making choices about pollution
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Choices concerning fighting pollution can be made on many levels:
International
e.g. The Kyoto protocol in 1997
National
e.g. Car tax system, subsidies for greener technology
Local
e.g. Recycling schemes, transport, congestion charges
Personal
e.g. Recycling, individual travel, reducing energy usage in the home etc