- The early atmosphere was formed from gases that escaped from volcanoes.
- These gases were water vapour and carbon dioxide.
Scientists analyse rocks that formed at differnet times to provide evidence for how the atmosphere has changed. Volcanic planets like Mars are also used as evidence.
- Oxygen is 1 of the most reactive gases in the atmosphere.
- Oxidation reacions can be seen in rusting metals and the maintenance of fire.
- The type of iron compounds found in rocks shows the oxygen content of the atmosphere. This provides evidence of the levels increasing over time.
- Nitrogen has increased and carbon dioxide has dramatically decreased.
- The evolution of life has changed the atmosphere.
carbon dioxide (g) + water (l) -> glucose (aq) + oxygen (g)
'g' = gas 'l' = liquid 'aq' in solution or dissolved in water
- As Earth cooled, water vapour in the atmoshpere condensed and fall as rain, making oceans.
- Carbon dioxide dissolved into the oceans, causing the percentage in the atmsophere to drop.
- Early sea plants used the CO2 for photosynthesis, releasing oxygen into the atmosphere.
- Sea animals took in CO2 to make shells. Shells from dead animals collected on the sea floor and turned into carbonate rocks over the years.
- Water (H2O) can either be a solid, liquid or gas.
- When water vapour condenses, intermolecular forces hold the molecules together.