Gases in the air

  • 78% nitrogen
  • 21% oxygen
  • 1% other gases
  • oxygen gas reacts with most metals to make solid metal oxides
  • we can find the percentage of oxygen in the air by passing air over heated copper
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The Earths Atmosphere

  • the Earths atmosphere was probably formed about 4 billion years ago by gases given out by volcanoes
  • Volcanoes release huge amounts of carbon dioxide and water vapour, they also release lava and dust
  • the Earths early atmosphere was mainly carbon dioxide
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Human activity and air quality

  • humans are changing gases in the atmosphere by burning fuels
  • fuels are used in factories, power stations, for transport, and in homes
  • pollutant gases include carbon monoxide, nitrogen oxides, and sulfur dioxide
  • carbon dioxide is linked to climate change by acting as a greenhouse gas trapping heat in the atmosphere
  • when air pollution levels are high, more deaths from athsma heart disease and lung disease occur, there is a correlation between air quality and health
  • sulfur dioxide and nitrogen dioxide are pollutants that make acid rain
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Measuring air quality

  • small amounts of carbon dioxide in the air are measured in parts per million, 1 ppm means there is 1 gram of the pollutant per 1 million grams of air
  • other pollutant gases are measured in parts per billion
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Burning fuels

  • Oxygen is needed for any fuel to burn and release energy
  • fossil fuels such as petrol, diesel and fuel oil are mainly hydrocarbons
  • hydrocarbons only contain hydrogen and carbon atoms
  • when a hydrocarbon fuel burns; HYDROCARBON FUEL+OXYGEN--->CARBON DIOXIDE+WATER(+ENERGY)
  • oxidation is when oxygen is added to a substance
  • reduction is when oxygen is removed from a substance
  • combustion is an oxidation reaction
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Chemical Reactions

  • atoms do not change, in chemical reactions atoms get rearranged to make new substances
  • atoms of non-material elements join to form molecules
  • elements are rearranged to make new compounds in chemical reactions
  • atoms in reactants are rearranged into new products with different properties
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Burning Sulfur

  • sulfur is insoluble but sulfur dioxide dissolves in water to make an acid solution
  • when fossil fuels burn sulfur burns, because fossil fuels contain small amounts of sulfur from the plants and animals that formed them
  • coal often contains sulfur
  • acid rain lowers the pH when it falls on land or enclosed water, harming living things or eroding carbonate rock
  • acid rain does not affect humans directly, so it is an indirect pollutant
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Pollutants

  • power stations and transport make most pollution because they burn most fuel
  • electricity production and transport has increased over the last century
  • if not enough air is available to burn the fuel, poisonous carbon monoxide is made and carbon particulates are made
  • car engines make nitrogen oxides when nitrogen and oxygen from the air react at high temperatures, this contributes to acid rain
  • carbon monoxide are formed during incomplete combustion
  • nitrogen monoxide is formed in furnaces and engines at a temperature at about 1000 degrees
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Monitoring air quality

  • pollutants are removed from the air when particulate carbon settles on surfaces, carbon dioxide is used by plants for photosynthesis, carbon dioxide dissolves in rain water
  • reducing electricity reduces fossil fuel use in power stations
  • wet scrubbing methods used to remove sulfur dioxide from power station waste gases: using an alkaline solution of calcium oxide and water which can be sold as plaster, and using sea water which absorbs sulfur dioxide
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Replacing fossil fuels

  • an alternative to fossil fuels is biofuels, which are made from plants
  • biofuels are carbon neutral, so when they burn they release the same amount of carbon dioxide that the plant origionally took to grow
  • large areas of land are needed to grow biofuels
  • fossil fuels are not renewable, so are not sustainable
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Reducing air pollution

  • air pollution from vehicles can be reduced by using cars less, using cleaner fuels, and using more public transport
  • catalytic converters contain a platinum catalyst that allows gases to react with eachother, CARBON MONOXIDE+NITROGEN MONOXIDE--->NITROGEN+CARBON DIOXIDE 
  • carbon monoxide gains oxygen so it is oxidised
  • nitrogen monoxide loses oxygen so it is reduced
  • legal limits for exhaust emissions are enforced by strict MOT tests
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