9.1.1

Proportions of Gases in the Atmosphere

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Importance of Atmospheric Gases

The Earth's atmosphere contains numerous gases, each of which has an effect on the success of our planet's organisms.

Nitrogen

  • Nitrogen is a key component of proteins, which are essential for growth.
  • Whilst it is abundant in the atmosphere, the producers found at the base of food chains are not able to exploit this source. Instead, they must absorb nitrogen in the form of soluble nitrates from the soil.

Oxygen

  • Oxygen is a reactant in respiration - a chemical reaction that takes place in all living cells.
  • As humans, we breathe oxygen into our lungs. From here, it diffuses into our blood and is carried to all the cells in our body.

Carbon dioxide and water vapour

  • Carbon dioxide and water vapour are greenhouse gases.
  • Greenhouse gases absorb and then re-radiate heat energy that is reflected off the Earth's surface. This is known as the greenhouse effect.
  • If the greenhouse effect is too strong, it can lead to global warming.

The Earth's Early Atmosphere

The Earth was formed roughly 4.6 billion years ago. We don't have much evidence from that long ago, but the common view (consensus view) among scientists is:

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Age of the volcanoes

  • Highly active volcanoes were littered across the Earth's surface for the first billion years of its existence.
  • The frequent eruptions of these volcanoes resulted in the release of lots of carbon dioxide (as well as smaller amounts of gases such as water vapour, methane, ammonia and nitrogen).
  • Scientists think carbon dioxide dominated the early atmosphere in a similar way to modern-day Mars.
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Reduction of carbon dioxide levels

  • Levels of atmospheric nitrogen accumulated steadily.
  • The oceans were formed as a result of the water vapour condensing.
    • The formation of the oceans caused a significant reduction in carbon dioxide levels in the atmosphere.
    • Carbonate precipitates were produced by reactions between the dissolved carbon dioxide and seawater. These precipitates were deposited as sediment.

Jump to other topics

1Atomic Structure

2Chemical Bonding

3Quantitative Chemistry

4Chemical Changes

5Energy Changes

6The Rate & Extent of Chemical Change

7Organic Chemistry

8Chemical Analysis

9Chemistry of the Atmosphere

10Using Resources

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