Gases in the Atmosphere

Topic 9 - Chemistry of the Atmosphere
Written By Atheridge Tuition

AQA-style Exam Question

The percentages of gases in the Earth’s early atmosphere have changed. Explain* these changes, based on Table 1.

[6 marks]

A chemistry exam question layout showing Table 1, which compares the approximate percentages of oxygen, carbon dioxide, and nitrogen in Earth's early atmosphere versus the modern atmosphere

*Explain = tell us HOW or WHY these changes happened

    • Oxygen has increased..

    • Carbon dioxide has decreased.

    • Nitrogen has increased.

Table 1 with rows highlighted in color: oxygen in blue, carbon dioxide in pink, and nitrogen in teal, asking students if each gas increased or decreased.

  • Algae/ plants carried out photosynthesis which releases oxygen.

A minimalist vector diagram of green aquatic algae performing photosynthesis, with a blue arrow showing the release of oxygen gas into the atmosphere.

  • Algae/ plants carried out photosynthesis, which absorbs carbon dioxide.

    Carbon was then stored in fossil fuels.

A vector illustration showing a green plant absorbing carbon dioxide, with a red arrow pointing down to a layer of black fossil fuels, demonstrating how carbon became locked away over millions of years.

  • Carbon dioxide was dissolved in the ocean.

    This formed sediments which then formed sedimentary rocks.

A vector diagram showing carbon dioxide dissolving into a blue body of water and a red arrow pointing down to grey sedimentary rocks, illustrating carbonate precipitation.

  • Volcanic activity released nitrogen gas.

A vector illustration of a grey volcano erupting with orange lava, showing a blue arrow indicating the release of nitrogen gas into the atmosphere. The adjacent bacteria graphic is faded out.

  • Denitrifying bacteria released nitrogen gas.

A vector diagram of a brown microbe labeled denitrifying bacteria with a blue arrow showing the production and release of nitrogen gas. The adjacent volcano graphic on the left is faded out.
 
 

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