GCSE AQA Chemistry 1 Earth & Atmosphere

GCSE AQA Chemistry 1 Earth & Atmosphere

1. Plate Tectonics

   • Wegener's theory of Continental Drift
     • Noticed records of v. similar fossils on opposite sides of Atlantic Ocean
       • Accepted theory was 'land bridges'
     • Coastlines of Africa & South America matched like jigsaw
       • Evidence: Matching layers in rocks
         • Fossils found in 'wrong' places
     • Theory: 300 million yrs ago, 1 'supercontinent' (Pangaea) that broke into smaller chunks that are drifting apart
       • Wasn't accepted for many yrs
         • Thought continents 'ploughing through' sea bed
           • Impossible - would have stopped Earth rotating
         • Had used inaccurate data
           • Found new evidence in 1950s & 60s

2. Earth's Structure

   • Crust: v. thin, surrounded by atmosphere
   • Mantle: has all properties of solid but can flow, radioactive decay takes place, produce heat - flows in convection currents
   • Core: made of Fe & Ni
   • Surface made of tectonic plates
     • Convection currents cause plates to drift
       • Most moving at speeds of few cms per yr
         • Occasionally plates move v. suddenly - earthquake
           • Volcanoes & earthquakes occur at boundaries
             • Can't predict - sometimes ground bulges but can be false alarm

3. The Evolution of the Atmosphere

   • Phase 1
     • Molten - atmosphere boiled away
       • Eventually cooled down - thin crust & volcanoes
         • Gases - carbon dioxide, methane & ammonia
           • Oceans formed when water vapour condensed
     • Phase 2
       • Green plants evolved - carbon dioxide absorbed & oxygen produced
         • Carbon & hydrocarbons locked up in sedimentary rocks as insoluble carbonates & fossil fuels
       • Phase 3
         • Ozone layer allows evolution of complex animals - blocks harmful rays

4. Primordial Soup

   • Earth's atmosphere rich in N, H, ammonia & methane
     • Lightning struck --> amino acids
       • Collected in primordial soup --> organic matter & living organisms
         • Miller Urey experiment - not as many made

5. Fractionally distilling air

   • Air filtered to remove dust, cooled to around -200*C - liquid
     • Water vapour condenses & removed
       • Carbon dioxide freezes & removed
         • Liquefied air enters column & heated slowly
           • Gases separated - oxygen & argon together - require another column