Chemistry (C1)

Chemistry (C1)

Topic one - The Earth's Sea and Atmosphere
1. The Evolution of the Atmosphere
  1. The Earth's atmosphere is made up of gases.
    1. Nitrogen (78%)
    2. Oxygen (21%)
    3. CO2 (0.004%)
    4. Other gases (1%)
  2. Phase 1
    1. 1) Earth's surface was molten for millions of years, it was too hot so any atmosphere would just boil away.
    2. 2) When things cooled down, a thin crust formed on the Earth's surface. Volcanoes kept erupting.
    3. 3) Volcanoes gave out lots of gas - Carbon dioxide, water vapor etc. and this is how it is thought that oceans and the atmosphere were formed.
    4. 4) According to this theory, the early atmosphere was most likely CO2, with virtually no oxygen.
    5. 5) The oceans formed when the water vapor condensed.
  3. Phase 2
    1. 1) A lot of the early CO2 dissolved into the oceans.
    2. 2) Marine organisms developed and took in some of this CO2. When they died they were buried under layers of sediment and the CO2 became "locked up in carbonate rocks.
    3. 3) Green plants evolved over most of the Earth. They also removed CO2 from the air and produced O2 by photosynthesis. Helping the oxygen to gradually increase.
  4. Phase 3
    1. 1) The build-up of oxygen in the atmosphere killed off some early organisms that couldn't tolerate it, but it allowed other, more complex organisms to live and flourish.
    2. 2) The oxygen also created the ozone layer which blocked harmful rays from the sun and enabled even more complex organisms to evolve.
    3. 3) There is very little CO2 left now.
2. Today's Atmosphere
  1. Evidence for how the atmosphere evolved has been found in rocks and other sources, but there are just theories.
  2. Changes in the Atmosphere
    1. Human Activity
      1. Burning fossil fuels - this releases CO2
      2. Deforestation - Less trees for photosynthesis, means more CO2 left
      3. Livestock farming - releases a lot of methane (when animals pass wind)
    2. Volcanic activity
      1. Sulfur dioxide - Forms smog
      2. Carbon dioxide - released during eruptions
    3. A lot of evidence of atmospheric change found out from antarctic ice cores
      1. Each year, a layer of ice forms and bubbles of air get trapped inside it, then that is buried in the next layer.
      2. The deeper the ice, the older the air
      3. If you examine the bubbles, you can see how the air has changed over the years. (changes between layers can be very, very tiny)
  3. CO2 is a greenhouse gas and there's a general consensus that rising levels are causing global warming
Topic Two - Materials From the Earth
1. Rocks

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