C1 - Air Quality

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  • C1 - Air Quality
    • Evolution of the atmosphere
      • Atmosphereformed by:
        • Gases given out by volcanoes
          • eg. carbon dioxide, water vapour, nitrogen
      • Build up of oxygen killed some early organisms
        • But other complex organisms evolved
      • Green plants removed oxygen from air
        • Replaced it with carbon dioxide by photosynthesis
      • Earth's surface was molten
        • Crust formed when everything cooled
          • Water vapour condensed forming oceans
    • Today's atmosphere
      • Nitrogen (78%)
      • Oxygen (21%)
      • Argon (1%)
      • 5 pollutants
        • Carbon dioxide
          • Removed from atmosphere by photosynthesis
            • Dissolves in rainwater & seas, lakes, rivers etc.
          • Dissolves in rainwater & seas, lakes, rivers etc.
        • Carbon monoxide
        • Particulates
          • Tiny particles in air
        • Sulfur dioxide
          • Leaves atmosphere as acid rain
          • Reacts with moisture in clouds & forms dilute sulfuric acid
        • Nitrogen oxides
        • Chemicals that are harmful as they are in the wrong place
    • Fossil Fuels
      • Usually hydrocarbons
        • Hydrogen + carbon
      • Formed by remains of dead animals & plants
        • Over millions of years
      • eg. crude oil
        • Drilled out of Earth & refined to make petrol/diesel
      • Hydrogen in fuel reacts with oxygen in air = water
        • Burn more rapidly with pure oxygen present rather than just in air
      • Carbon in fuel reacts with oxygen in air = carbon dioxide
      • React at such high temperatures; nearby atoms in air react with each other
    • Chemical Reactions
      • Occur when atoms are rearranged
      • No mass is lost - mss of reactants = mass of product
      • Burning is called combustion
      • Oxygen is added = oxidation reaction
        • If not enough oxygen is available, carbon monoxide is produced = incomplete burning
      • Oxgen is lost = reduction reaction
        • If not enough oxygen is available, carbon monoxide is produced = incomplete burning
    • Reducing pollution
      • Wet scrubbing = dilute sulfuric acid removed from flue gases
        • Reacts with alkalis
          • eg. seawater
            • Sulfur dioxide dissolves in seawater producing carbon dioxide, water & dissolved sulfate
          • eg. alkaline slurry
            • Sprayed onto gases
              • Sulfur dioxide reacts with alkaline producing solid waste product
      • Catalytic converter
        • Convert harmful nitrogen monoxide into harmless nitrogen & oxygen
          • Reduction reaction
            • Loses oxygen
        • Convert carbon monoxide into carbon dioxide
          • Oxidation reaction
            • Adds oxygen
      • Biofuels
        • Renewable energy source
          • Produced carbon dioxide when burned
            • Carbon neutral
          • Carbon neutral

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