Earths Atmosphere

Question 1

Break down of air:

Answer 1

78% - Nitrogen N2
21% - Oxygen O2
0.04% - Carbon dioxide CO2
<1% - other gases

Question 2

how has the earths atmosphere changed over the last 4 billion years? (4 marks)

Answer 2

• Earth cooled and volcanoes gave out: -carbon dioxide, ammonia, methane, water vapour
• Water vapour condensed to form oceans
  CO2 –> O2 (photosynthesis)
• Carbon dioxide got “locked up” in plants to form limestone + coal (fossil fuels)
• Oxygen built up and formed ozone layer

Question 3

Miller-Urey Theory on how life on earth formed:

Answer 3

1. billions of years ago
2. “Primordial soup”
3. N2, H2, CH4, NH3
4. Lightning
5. Amino acids
6. Proteins
7. Life