C1 : Air Quality

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  • C1 - Air Quality
    • The Atmosphere
      • Pollutants
        • Concentrations measured in ppb (parts per billion) or ppm (parts per million)
        • Measurements must be repeated as results may vary depending on time of day, traffic, and weather
          • Repeated results allow a chemist for mean which will give a god estimate for the true concentration value.
        • Chemicals that are harmful to the environment and our health.
        • Released into the atmosphere by burning fossil fuels eg cars and power stations
        • Indirect harm : acid rain makes rivers too acidic for organisms to survive - affects food chain and natural resources eg trees.
      • Atmosphere : Thin layer of gases
      • 78% Nitrogen, 21% oxygen, 1% argon and noble gases, 0.02 water vapour, co2 and other gases
      • Early atmosphere : created by volcanic activity and mainly water vapour and carbon dioxide
        • Earth cooled and water vapour condensed to oceans
          • Simple Photosynthetic organisms evolved in oceans adding oxygen and removing co2
            • Some Co2 was removed due to it dissolving in oceans and forming sedimentary rock and fossil fuels
    • Pollution
      • Effect
        • pollutants released in the atmosphere must go somewhere as they cannot just disappear which cause environmental problems
          • Particulates of Carbon land on surfaces making them dirty
          • Carbon removed naturally : dissolved in rain (causes reactions) and seawater, photosynthesis
            • Too much carbon is being produced so the levels increase each year as it cannot be balanced out naturally
        • Sulphur and Nitrogen Dioxide react with water to produce acid rain : damages trees, corrodes metal, unbalances the pH of rivers
      • Reducing
        • Power Stations
          • Using less electricity.
          • Removing sulphur an toxic chemicals from gas, coal and oil before burning
          • Use alternate sources eg hydroelectric, solar, wind
          • Wet Scrubbing with either seawater or calcium oxide and water spray
        • Cars
          • Use low-sulphur fuel in engines with modern fuel-efficient engines
          • legal limits for exhaust emissions enforced by MOT tests
          • Use public transport
          • Use cars with catalytic converters (reduce Co and No in engine exhaust gases.
          • Electric cars but must be produced renewably.
          • Biofuels instead of fossil fuels but they use up valuable farmland
        • Burn fewer fossil fuels but population increasing every year = increased energy demand
      • Chemicals
        • Combustion
          • Complete
            • When there is enough oxygen for fuel to burn completely.
              • Petrol, fuel oils and diesel consist mainly of compounds called hydrocarbons eg methane
                • Hydrocarbons : only hydrogen and carbon atoms : produce Co2 and water (Hydrogen oxide) when burned in air.
          • Incomplete
            • When there is not enough oxygen present.
              • Depending on amount of oxygen present carbon particulates or carbon monoxide may be produced.
            • Occurs in car engines. exhaust emissions contain carbon particulates and carbon monoxide as well as carbon dioxide
            • Coal can contain sulphur so sulphur dioxide is released when its burned.
        • Over 100 elements each made from tiny particles called atoms.
        • Reactions form new substances from old ones: reactants rearranged to make products : joined atoms may separate : separate atoms may be joied : joined atoms may be spereated and joined again in different ways
          • Usually not easily reversed
          • No atoms are created or destroyed during a reaction so the total mass stays the same (mass is conserved)


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