Today's Atmosphere

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.