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Year 9

The carbon cycle

I can describe the carbon cycle and explain the effect of changes to parts of the cycle.

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New
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Year 9

The carbon cycle

I can describe the carbon cycle and explain the effect of changes to parts of the cycle.

Download all resources
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Share activities with pupils
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These resources will be removed by end of Summer Term 2025.

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Lesson details

Key learning points

  1. Combustion increases the amount of carbon dioxide in the atmosphere.
  2. Respiration of living things increases the amount of carbon dioxide in the atmosphere.
  3. Decomposition of dead plants and animals increases the amount of carbon dioxide in the atmosphere.
  4. Photosynthesis by plants, phytoplankton and some bacteria reduce the amount of carbon dioxide in the atmosphere.
  5. Carbon dioxide can dissolve in the oceans.

Keywords

  • Carbon cycle - the process by which carbon is transferred between the atmosphere, organisms, and Earth

  • Photosynthesis - the process in which energy from sunlight converts carbon dioxide and water into glucose and oxygen

  • Respiration - a chemical process in cells that breaks down glucose from food to release energy for life processes

  • Combustion - an exothermic chemical reaction in which a substance reacts with oxygen, releasing heat to the surroundings

  • Decomposition - the breakdown of dead organic matter by microorganisms

Common misconception

Carbon atoms can be created or destroyed.

Focus teaching on the carbon cycle as a closed system in which the total amount of carbon is constant. Discuss the processes of how carbon is transferred from one place to another, rather than processes of how carbon is lost or gained.


To help you plan your year 9 science lesson on: The carbon cycle, download all teaching resources for free and adapt to suit your pupils' needs...

For some classes, card sort activities can be useful for consolidating understanding. For some, it can help clarify understanding by providing opportiunity for pupils to work in small groups to write summaries, in their own words, of each part of the lesson/carbon cycle.
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This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
Which of the following do not photosynthesise?
oak trees
Correct answer: humans
grass
green algae
Q2.
What is the molecular formula of carbon dioxide?
CO³
CO₃
CO²
Correct answer: CO₂
Co₂
Q3.
What three things are required for combustion?
fuel, carbon dioxide and water
fuel, heat and water
Correct answer: fuel, heat and oxygen
carbon dioxide, oxygen and water
Q4.
Which of the following is the correct word equation for respiration?
carbon dioxide + glucose → water + oxygen
Correct answer: oxygen + glucose → carbon dioxide + water
carbon dioxide + water → oxygen + glucose
oxygen + water → carbon dioxide + glucose
Q5.
What key term describes the break down of dead organic matter?
Correct Answer: decomposition, decomposing, decompose
Q6.
Look at the image of a food chain. What happens to the carbon atoms in the plant?
An image in a quiz
Correct answer: Carbon atoms are moved to the caterpillar when it eats the plant.
Carbon atoms are moved from the caterpillar to the plant when it is eaten.
Correct answer: Carbon atoms from the plant move into the soil when it dies.
Carbon atoms get broken up when the plant is eaten.

Exit quiz

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6 Questions

Q1.
What is the process that uses energy from sunlight to convert carbon dioxide and water into glucose and oxygen?
Correct Answer: photosynthesis
Q2.
Which of the following processes transfer carbon dioxide into the atmosphere?
photosynthesis
Correct answer: combustion
Correct answer: respiration
eating
dissolving
Q3.
How does decomposition affect the amount of carbon in the atmosphere?
Correct answer: it transfers carbon into the atmosphere
it transfers carbon out of the atmosphere
it doesn't transfer carbon into or out of the atmosphere
Q4.
Which of the following processes transfer carbon dioxide out of the atmosphere?
respiration
Correct answer: photosynthesis
decomposition
Correct answer: dissolving
combustion
Q5.
Which of the following is not a way in which carbon is transferred during the carbon cycle?
Carbon is transferred into animals when they eat.
When animals and plants die, carbon is transferred into the soil.
Correct answer: Decomposition transfers carbon dioxide out of the atmosphere.
Combustion transfers carbon dioxide into the atmosphere.
Carbon is transfers into sedimentary rocks when shells are cemented together.
Q6.
Sort the following statements into order to explain how carbon in the oceans can end up in rock.
1 - Dissolved carbon dioxide forms carbonate ions.
2 - The bodies of some animals can use these to make shells or bones.
3 - Shells and bones of dead sea creatures drop to the bottom of the ocean.
4 - They are compacted together.
5 - Clay or minerals cement them together.
6 - At this stage a sedimentary rock will have been formed.