C9 - Chemistry of the Atmosphere

Question 1

What is the chemical composition
of the atmosphere?

Answer 1

78% Nitrogen
21% Oxygen
1% Argon and other gases
Carbon dioxide is 0.04%

Question 2

How and why has the amount of
water vapour in the atmosphere
changed since the Earth formed?

Answer 2

The amount of water vapour has
decreased.
As the Earth cooled the water vapour
condensed to form the oceans.

Question 3

How and why has the amount of
oxygen in the atmosphere changed
since the Earth formed?

Answer 3

The amount of oxygen has increased
since green plants evolved and began
photosynthesis releasing oxygen.

Question 4

How and why has the amount of carbon dioxide in the atmosphere changed since the Earth formed?

Answer 4

The amount of carbon dioxide has
decreased as carbon dioxide is:
1 – stored in plants
2 – stored in carbonate rocks
3 – dissolved in the oceans
4 – stored in fossil fuels

Question 5

Why have nitrogen levels
increased since the Earth formed?

Answer 5

Nitrogen levels have steadily increased because volcanoes release it. It is not very reactive so is not easily removed.

Question 6

What is the word equation for
photosynthesis?

Answer 6

carbon dioxide + water - - - -> oxygen + glucose

Question 7

What are the main green house gases?

Answer 7

Carbon dioxide
Methane
Water vapour

Question 8

Describe the green house effect?

Answer 8

Short wavelength radiation from the sun passes through the atmosphere and is absorbed by the Earths surface warming it.
The warm Earth emits longer wavelength radiation that cannot travel trough the atmosphere.
This radiation is trapped and warms the atmosphere

Question 9

How do humans contribute to the
green house effect?

Answer 9

Through activities that release carbon dioxide or methane.
For example:
-Burning fossil fuels to generate electricity.
-Burning fossil fuels in cars.
-Farming large amounts of cattle that produce methane.
-Deforestation

Question 10

What other atmospheric pollutants
are released from burning fuels and
what are their effects?

Answer 10

• Carbon monoxide is a toxic gas. It is colourless and odourless and so is not easily detected.
• Sulfur dioxide and oxides of nitrogen cause respiratory problems in humans and cause acid rain.
• Particulates (Soot) cause global dimming and health problems for humans.