AQA GCSE Chemistry

Revision Notes

9.1.4 How Carbon Dioxide Decreased

Removal of Carbon Dioxide

  • Carbon dioxide is a water soluble gas (it is the gas used in fizzy drinks) and dissolves readily
  • When the water vapour in Earth’s early atmosphere condensed large amounts of CO2 dissolved in the oceans
  • Carbonates were precipitated during this process which later formed sediments on the seabed
  • As marine life began to evolve sea creatures began to appear which used up the carbonates to form shells and skeletons
  • Green plants and algae began to evolve and absorbed considerable amounts of carbon dioxide during photosynthesis
  • When these organisms died, their remains locked the atmospheric carbon into the rocks
  • This is how the large amounts of carbon dioxide in the early atmosphere were reduced

Exam Tip

Exhaled air contains about 4% carbon dioxide and 16% oxygen which is why mouth-to-mouth resuscitation can save someone who has stopped breathing.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.

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