C9

Question 1

What are the different gases in atmosphere?

Answer 1

Approximately: - 80% nitrogen - 20% oxygen - 1% others including: CO2; water vapour and noble gases.

Question 2

Why is knowledge on the Earth’s early atmosphere limited?

Answer 2

Because of the time scale of 4.6 billion years.

Question 3

How does the Earth’s atmosphere begin?

Answer 3

1. The Earth was covered with volcanoes which intensely erupted and released lots of gases. It was mainly like Mars / Venus (lots of CO2 and little O2) –> C02, N2, water vapour and small amounts of methane and ammonia.

Question 4

After volcanoes, what happens next to the Earth’s atmosphere?

Answer 4

2. Water vapour condenses which forms oceans. –> C02 absorbed in oceans so less CO2.

Question 5

After oceans are formed, what happens next to the Earth’s atmosphere?

Answer 5

3. Green plants and algae grow and evolve and absorb CO2 using photosynthesis. –> CO2 decreases

Question 6

After algae evolves, what happens next for the Earth’s atmosphere?

Answer 6

4. Some CO2 became locked up / stored in rocks by being buried and compressed over millions of years. –> Less CO2 in atmosphere. E.g. fossil fuels: coal, oil, natural gas.

Question 7

After CO2 stored in plants, what happens next for the Earth’s atmosphere?

Answer 7

5. Algae and green plants grow and with photosynthesis, they absorb CO2 and release O2 which allows animals to evolve. –> Around 200 million years ago, the composition reached the same as now.

Question 8

Photosynthesis word equation

Answer 8

Carbon dioxide + Water —-(light)—> Glucose + Oxygen

Question 9

Photosynthesis symbol equation

Answer 9

6CO2 + 6H20 –> C6H12O6 + 602

Question 10

When did algae first produce oxygen?

Answer 10

2.7 billion years ago.

Question 11

What are the 3 greenhouse gases?

Answer 11

Water vapour; CO2; Methane

Question 12

What’s the greenhouse effect?

Answer 12

• Electromagnetic radiation at most wavelengths passes through the Earth’s atmosphere. - The Earth absorbs most of the radiation and warms up. - The Earth radiates energy as infrared radiation. - Some of the infrared radiation goes into space. - Some of the infrared radiation is absorbed by greenhouse gases in the atmosphere. - The lower atmosphere warms up.

Question 13

What are 3 things humans are doing to increase greenhouse gases?

Answer 13

• Deforestation (therefore increasing CO2) - Burning fossil fuels (therefore releasing CO2) - Agriculture (more animals means more methane)