GCSE Higher Chemistry revision notes.

  • Created by: katie
  • Created on: 08-06-12 11:20

Metals and the environment

  • Mining metal ores destroys the landscape, habitats, displaces local people, changing their way of life.
  • Using carbon to reduce metal ores produces carbon dioxide. This adds to carbon dioxide levels in the atmosphere.
  • Smelting ores containing sulfur produces sulfur dioxide which causes acid rain. If collected, the sulfur dioxide can be used to make useful sulfuric acid.
  • Recycling aluminium saves energy.
  • Brownfield sites are sites that haven't been used before. They are often polluted by toxic compounds of cadmium, nickel and cobalt.
  • Instead of removing the soil from these sites, developers now grow plants on them. These plants absorb the toxic metal ions making the land safe to use.
  • When burnt the plant ash contains compounds of the toxic metals that can be used as ores. This is phytomining.
  • Phytoming takes time, it's cheap and metal compounds are easily retrieved at the end.
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A burning problem

  • Global warming. Increasing carbon dioxide in the atmosphere traps more energy from the sun making the Earth warm up.
  • Global dimming. Dust particles in the air prevent sunlight reaching the ground. This reduces the energy available for photosynthesis, and may cool the earth as-well.
  • Both affect the weather patterns of the Earth.
  • Acid rain is caused by nitrogen, sulfur and carbon dioxide dissolving in rain water. The acid formed attacks limestone buildings much more quickly than normal rain. It can also cause serious damage to trees and to aquatic life in affected lakes.
  • Durning combustion, each carbon atom in a fuel needs two oxygen atoms to form carbon dioxide CO2.
  • If there's not enough air, some carbon atoms get only one oxygen atom (carbon monoxide), or none at all (carbon or soot).
  • Carbon monoxide is poisonous, it is easily absorbed by your red blood cells instead of oxygen, therefore depriving your body of oxygen.
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Reducing air pollution

  • Vehicles that burn fossil fuels produce poisonous carbon monoxide, and they also produce nitrogen oxides which cause acid rain.
  • To reduce the amount of these compounds released by vehicles all new cars have catalytic converters fitted.
  • Carbon monoxide is oxidised to carbon dioxide, and nitrogen oxides are reduced to nitrogen.
  • Alternative fuels are also being used such as bio-diesel made from vegetable oils, which contain almost no sulfur. Ethanol made by burning sugar. 
  • Reforests are cut down to grow sugar. this causes food prices to go up for everyone.
  • Hydrogen can only be obtained by using electricity to electrolyse water.
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