The modern atmosphere contains:
- 78% nitrogen
- 21% oxygen
- 1% argon
- 0.03% carbon dioxide
Iron oxide is formed when iron reacts with oxygen in the air.
We can measure the amount of it from a known volume of air, letting us see the amount of oxygen in the air.
- The gases in the air can be seperated by fractional distillation.
- The gases in the atmosphere change when volcanoes erupt, when humans burn fossil fuels and when forests are cut down.
- Burning fossil fuels, mainly hydrocarbons, release carbon dioxide.
- Extra carbon dioxide is released when volcanoes erupt.
- Forests carry out photosynthesis, reducing the amount of carbon dioxide. Deforestation decreases the amount of carbon dioxide taken away from photosynthesis.
- Atmospheric carbon dioxide levels have increased over the years due to human activity.
- Farmers with fertilisers increases the amount of nitrogen oxides in the atmosphere. Cattle farming increases levels of methane.