Compared to the Earth's early atmosphere, the modern atmosphere contains:
Name the most abundant gas in the modern atmosphere.
The Earth cooled after it formed. When it became cool enough, water vapour in the atmosphere condensed to liquid water. It fell as rain, creating the oceans.
Carbon dioxide + water → glucose + oxygen
6CO2(g) + 6H2O(l) → C6H12O6(aq) + 6O2(g)
Photosynthesis by primitive plants and algae caused the removal of carbon dioxide from the air and the release of oxygen. This had two effects:
Oxygen supports combustion. If oxygen is present in a test tube, a glowing splint relights when it is held inside.
Describe two reasons why the amount of carbon dioxide in the atmosphere decreased over time.
Carbon dioxide dissolved in the oceans and primitive plants used it for photosynthesis.