4.9 Chemistry of the Earth's Atmosphere

Question 1

How old is the earth?

Answer 1

About 4.6 billion years old

Question 2

For the first 200 million years, what was the most abundant gas in the atmosphere?

Answer 2

Carbon dioxide

Question 3

How did the oceans form?

Answer 3

1. Water vapour which was released from volcanoes cooled and condensed, falling as rain.
2. Comets, made mainly of ice, collided with the earth, bringing more water the the planet.

Question 4

What is the percentage abundance of nitrogen in our atmosphere today?

Answer 4

approximately 80%

Question 5

What is the percentage abundance of oxygen in our atmosphere today?

Answer 5

approximately 20%

Question 6

What is the percentage abundance of carbon dioxide in our atmosphere today?

Answer 6

0.04%

Question 7

Where did the nitrogen in our atmosphere come from?

Answer 7

Volcanic activity

Question 8

Why is there only limited evidence to inform theories on the evolution of the atmosphere?

Answer 8

Because of the huge timescale involved - 4.6bn years.

Question 9

How did the oceans contribute to the reduction of carbon dioxide in our atmosphere?

Answer 9

As the planet cooled and water vapour condensed, carbon dioxide in the atmosphere dissolved into the water. From here, carbonates formed, precipitating out of the water to form sediment (and therefore “locking up” the carbon).