C9- Chemistry of the Atmosphere

Question 1

Give the proportions of Gases in the Earth’s Atmosphere.

Answer 1

• 78% Nitrogen
• 21% Oxygen
• 0.04% Carbon Dioxide
• <1% Argon
• <1% Other gases

Question 2

Why is Nitrogen a key component for the success of our planets organisms?

Answer 2

• Nitrogen is a key component of proteins, which are essential for growth.
• Plants absorb nitrogen in the form of soluble nitrates from the soil.

Question 3

Explain how the Earth’s Early atmosphere (the first billion years) was formed.

Answer 3

• During the first billion years there was a lot of volcanic activity which released a lot of gases into the atmosphere.
• Scientists believed that the early atmosphere was most concentrated with Carbon Dioxide with no oxygen, similar to the atmospheres of Venus and Mars today.
• It is believed that the volcanic activity also released nitrogen, which built up in the atmosphere over time, as well as water vapour and small amounts of methane and ammonia.

Question 4

How did the oceans form after the period of high volcanic activity?
How did the oceans forming resulting in decreasing Carbon Dioxide levels?

Answer 4

• The oceans formed due to the water vapour released by volcanoes condensing as the earth began to cool.
• The Carbon Dioxide in the atmosphere began to dissolve in the newly formed oceans and formed a weak acid.
• The weak acid reacted with minerals in the seas and oceans to form precipitates.
• Over time these precipitates formed carbonate rock on the sea bed.
• Some of the carbon dioxide in the water was used to make corals and shells of organisms. When these organisms died they formed limestone which also decreased the levels of Carbon Dioxide.

Question 5

How did oxygen begin to increase in the early atmosphere?

Answer 5

• 2.7 billion years ago algae evolved in the oceans, photosynthesis carried out by these marine plants increased the levels of oxygen in the atmosphere and decreased the levels of carbon dioxide.

Question 6

Give 3 examples of fossil fuels.

Answer 6

• Coal
• Crude oil
• Natural gas

Question 7

Explain the process that creates fossil fuels.

Answer 7

• When plants, plankton or marine animals die, they fall to the sea bed and get buried under layers of sediment. Over millions of years they become compressed and form sedimentary rocks, oil and gas - they trap carbon dioxide with them.