C1.1 The Early Atmosphere

Oxygen is the most reactive gas in out atmosphere. Oxidation reactions can be seen in rusting metals.
The type of iron compounds found in rocks show a record of oxygen content at the time the rock was formed
1. recent rocks contain iron oxide, but iron in older rocks is not oxidised. This proves that the amount of oxygen in our atmosphere has increased.
Nitrogen levels have increased and oxygen levels have dramatically decreased.
the evolution of life caused major changes to the gases in our atmopshere
our atmosphere has formed from gases that escaped from volcanoes
a long time ago, the main gases in our atmosphere were water vapour and carbon dioxide
rocks contain a record of gases present in the atmosphere at the time they formed
1. this allows scientists to see how the atmosphere has changed
as the eart cooled, water vapour in the atmosphere condensed and fell as rain to create out oceans
1. the carbon dioxide in the atmosphere at the time dissolved into the water, causing the percentage to drop
  1. early sea plants used this carbon dioxide for photosynthesis and released oxygen into the atmosphere, causing percentages to rise.
2. some sea animals took in carbon dioxide to make their shells. shells fromm dead sea animals collected on the floor of the oceans and turned into carbonate rocks
when water condenses, intermolecular forces hold the molecules together = H20
photosynthesis decreased levels of co2 and increased levels of o2
1. 6CO2 + 6H2O => C6H12O6 + 6O2
  1. carbon dioxide + water => glucose + oxygen +(energy)

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C1.1 The Early Atmosphere

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