GCSE AQA Chemistry 1 Earth & Atmosphere

Plate Tectonics
1. Wegener's theory of Continental Drift
  1. Noticed records of v. similar fossils on opposite sides of Atlantic Ocean
    1. Accepted theory was 'land bridges'
  2. Coastlines of Africa & South America matched like jigsaw
    1. Evidence: Matching layers in rocks
      1. Fossils found in 'wrong' places
  3. Theory: 300 million yrs ago, 1 'supercontinent' (Pangaea) that broke into smaller chunks that are drifting apart
    1. Wasn't accepted for many yrs
      1. Thought continents 'ploughing through' sea bed
        Impossible - would have stopped Earth rotating
      2. Had used inaccurate data
        Found new evidence in 1950s & 60s
Earth's Structure
1. Crust: v. thin, surrounded by atmosphere
2. Mantle: has all properties of solid but can flow, radioactive decay takes place, produce heat - flows in convection currents
3. Core: made of Fe & Ni
4. Surface made of tectonic plates
  1. Convection currents cause plates to drift
    1. Most moving at speeds of few cms per yr
      1. Occasionally plates move v. suddenly - earthquake
        Volcanoes & earthquakes occur at boundaries
        Can't predict - sometimes ground bulges but can be false alarm
The Evolution of the Atmosphere
1. Phase 1
  1. Molten - atmosphere boiled away
    1. Eventually cooled down - thin crust & volcanoes
      1. Gases - carbon dioxide, methane & ammonia
        Oceans formed when water vapour condensed
  2. Phase 2
    1. Green plants evolved - carbon dioxide absorbed & oxygen produced
      1. Carbon & hydrocarbons locked up in sedimentary rocks as insoluble carbonates & fossil fuels
    2. Phase 3
      1. Ozone layer allows evolution of complex animals - blocks harmful rays
Primordial Soup
1. Earth's atmosphere rich in N, H, ammonia & methane
  1. Lightning struck --> amino acids
    1. Collected in primordial soup --> organic matter & living organisms
      1. Miller Urey experiment - not as many made
Fractionally distilling air
1. Air filtered to remove dust, cooled to around -200*C - liquid
  1. Water vapour condenses & removed
    1. Carbon dioxide freezes & removed
      1. Liquefied air enters column & heated slowly
        Gases separated - oxygen & argon together - require another column

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GCSE AQA Chemistry 1 Earth & Atmosphere

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