Lesson T10.1.1

T10.1.1 The carbon cycle Quiz: KS3 Chemistry, Unit 10

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson T10.1.1, The carbon cycle: 20 multiple choice questions for the KS3 Chemistry (National Curriculum), Unit 10: Carbon cycle and atmosphere, written with Revision Ninja.

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The 20 questions

  1. Which process removes carbon dioxide from the atmosphere?

    • Respiration in living cells
    • Photosynthesis
    • Combustion of fuels in air
    • Decomposition by microbes

  2. Which processes release carbon dioxide into the atmosphere?

    • Respiration and combustion
    • Evaporation and melting
    • Photosynthesis and deposition
    • Weathering and erosion only

  3. Which carbon store holds the most carbon on Earth?

    • Rocks and sediments
    • The atmosphere above the ground
    • Living animals on land and sea
    • Plants alone in the forest

  4. How does carbon move from the atmosphere into the ocean?

    • Carbon dioxide forms salt crystals
    • Carbon dioxide dissolves in the sea water
    • Carbon dioxide turns into metal
    • Carbon dioxide is absorbed by rocks in a day

  5. What happens to carbon in animals when they eat plants?

    • It turns into a metal inside the animal's body over time
    • It passes into the animal's body as part of food
    • It is removed from the carbon cycle entirely by the animal
    • It is turned into oxygen gas inside the animal's body

  6. Which process returns carbon from dead plants and animals to the soil?

    • Decomposition by microorganisms
    • Sublimation of snow on mountain tops
    • Melting of ice on the sea surface
    • Photosynthesis in green leaves of plants

  7. Why is the carbon cycle described as a cycle?

    • Carbon is continuously recycled between stores and living things
    • Carbon moves in one direction only through the whole system
    • Carbon is only found in fossil fuels and in coal deposits
    • Carbon is used up and never returns to the air or soil

  8. Which process forms fossil fuels from dead organisms over long periods?

    • Burning in air at high temperatures for long periods
    • Melting in the atmosphere during warm weather
    • Freezing in glaciers over many thousands of years
    • Burial and compression under layers of sediment

  9. What links photosynthesis to the carbon cycle?

    • It turns carbon into oxygen gas only, with no sugar made
    • It removes carbon dioxide and turns it into glucose
    • It changes carbon into a rock layer over millions of years
    • It adds carbon dioxide to the atmosphere in large amounts

  10. Which process returns carbon from the atmosphere to rock over long timescales?

    • Respiration in animals and humans
    • Evaporation of ocean water into clouds
    • Formation of limestone from shells
    • Burning of coal in power stations

  11. Which process is the main way carbon enters the atmosphere from living things?

    • Erosion
    • Respiration
    • Condensation
    • Photosynthesis

  12. Which store of carbon is found in fossil fuels?

    • Oxygen in the atmosphere of the planet
    • Water vapour in clouds above land
    • Coal, oil and natural gas
    • Nitrogen in soil and plant roots

  13. What is the main form of carbon that moves through the atmosphere?

    • Carbon monoxide only
    • Carbon dioxide
    • Methane only
    • Pure solid carbon

  14. Which sequence correctly describes carbon moving through a food chain?

    • Plants take in carbon, animals eat plants, and decomposers release carbon
    • Rocks take in carbon, animals eat rocks, and plants release carbon
    • Decomposers take in carbon, plants eat decomposers, and animals release carbon
    • Animals take in carbon, plants eat animals, and rocks release carbon

  15. Which process returns carbon to the atmosphere when wood is burned?

    • Erosion
    • Combustion
    • Photosynthesis
    • Deposition

  16. Why does burying dead organisms in sediment matter for the carbon cycle?

    • It turns carbon into a liquid that drains away into the sea
    • It can lock carbon away in rocks or fossil fuels for a long time
    • It releases carbon back into the air immediately, as gas
    • It removes oxygen from the sediment layers below the surface

  17. Which carbon-containing compound do living things use as a source of energy?

    • Nitrogen
    • Glucose
    • Argon
    • Oxygen

  18. Which gas do animals breathe out that is part of the carbon cycle?

    • Oxygen gas in air
    • Nitrogen gas in air
    • Argon gas in air
    • Carbon dioxide

  19. Which store holds carbon in dead plant and animal material in the ground?

    • The upper atmosphere above the clouds
    • Liquid ocean water only, at depth
    • Solid iron cores deep in the planet
    • Soil and dead organic matter

  20. Which part of the carbon cycle links plants to animals?

    • Erosion of rock by rivers and streams
    • Feeding, as animals eat plants
    • Melting of ice caps in polar regions
    • Condensation of water vapour into clouds

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