C1: Air quality

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What is in the Atmosphere?

  • 78% Nitrogen 
  • 21% Oxygen
  • 1% Argon 

Human activity and volcanic eruptions have added gases and particulates to the air.

  • Particulates- tiny pieces of solid.
  • Many of these gases and particulates are pollutants - they affect air quality. 
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How was the atmosphere formed?

  • Early atmosphere - mainly Carbon dioxide and Water Vapour ( from volcanoes).
  • Earth cooled- Water vapour condensed into oceans.
  • Carbon dioxide dissolved in oceans- made sedimetary rocks. Some ended up in fossil fuels.
  • The amount of oxygen increased- photosynthesis in plants; took carbon dioxide from the atmosphere, added oxygen.
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How do reactions make air pollutants?

  • Coal is mainly Carbon. Petrol, Diesel and fuel oils are mainly Hydrocarbons.
  • Hydrocarbons- Compounds of Hydrogen and Carbon only.
  • Fossil fuels burn & react with Oxygen in the air. Products are; Carbon Dioxide and Water.
  • In a chemical reaction, the total mass of the products is equal to the total mass of the reactants.
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What are Oxidation and Reduction reactions?

  • Oxidation- adds oxygen to a chemical.
  • Burning of fossil fuels is an example of Oxidation.
  • Fuels burn more quickly in pure oxygen than in air.
  • Reduction- removes oxygen from a chemical.
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Where do Air Pollutants come from?

  • Burning fossil fuels makes Carbon Dioxide. - If there isnt enough oxygen present, incomplete burning, Carbon Monoxide and particulate Carbon is made.
  • Some fossil fuels contain Sulfur. -when burnt, Sulfur reacts with Oxygen to form Sulfur Dioxide.
  • At high temperatures in an engine, Nitrogen and oxygen from the air react to form Nitrogen Oxides.- Nitrogen Monoxide forms first, reacts with more Oxygen, makes Nirogen Dioxide.
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What problems do air pollutants cause?

Pollutants do not just disappear. Some remain in the atmosphere and harm humans directly:

  • Carbon monoxide- Reduces the amount of Oxygen the blood can carry.

Some humans harm the environment, harm humans indirectly:

  • Sulfur dioxide and oxides of Nitrogen - React with Water and Oxygen to form acid rain.
  • Carbon dioxide- Contributes to climate change.
  • Carbon Particulates- Make surfaces dirty.
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How can we improve Air Quality?

  • Carbon dioxide- Burn less fossil fuels.

Power stations

  • Use less electricity.
  • Remove sulfur impurities form fuels before burning them.
  • Remove Sulfur dioxide and particulates from flue gases.

Sulfur dioxide(acidic) - Removed by reacting it with an alkali (Wet Scrubbing).

  • Sea water- Flue gases are sprayed with sea water.
  • Calcium oxide solution- reacts with Slfur dioxide to make Calcium Sulfate.
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How can we improve Air Quality ?(continued)


  • Develop efficient engines- burn less fuel.
  • Use low Sulfur fuels.
  • Use Catalytic coverters to:

- Add Oxygen to Carbon Monoxide.

-Remove Oxygen from Nitrogen Monoxide.

  • Use public transport.
  • Have legal Limits on exhaust emissions.
  • Fuel vehicles with biofuels or use electric cars.

-Biofuels- made from plants like sugar cane. They are Carbon neutral. The plants grow on land that could be used for food crops.

-Electric vehicles- Powered by batteries. Do not produce waste gases. The electricity may have been generated by burning fossil fuels and the cars need to be charged often.

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