Trace carbon transfers

Supplied materials

• All measurements and observations below are supplied classroom examples. They are not data from actual learners or a claim about a particular real site.
• Paper or a browser document for a labeled drawing, table or explanation.
• Worked problem inputs: Carbon enters a leaf as carbon dioxide and later exits through respiration. Explain whether the carbon atom is used up.
• Assessment case 1: A leaf takes carbon from CO₂ and incorporates it into organic molecules. What is conserved? Which inference or prediction is best supported?
• Assessment case 2: Which scientific label fits the specifically described step or feature? Supplied case: Cell releases carbon dioxide from fuel.
• Assessment case 3: Which scientific label fits the specifically described step or feature? Supplied case: Fuel carbon becomes carbon dioxide in fire model.
• Assessment case 4: Which scientific label fits the specifically described step or feature? Supplied case: Carbon remains in geological material.
• Assessment case 5: Which scientific label fits the specifically described step or feature? Supplied case: Algae take up carbon during photosynthesis.
• Assessment case 6: Respiration returns supplied organic carbon to CO₂. What follows? Which inference or prediction is best supported?

Learn the idea

Carbon moves among atmosphere, organisms, oceans and geological stores. Photosynthesis, respiration, decomposition and combustion transfer carbon through different processes. A store and a flow are different quantities.

Photosynthesis means carbon dioxide enters biological sugar production. Respiration means organic carbon returned as carbon dioxide. Combustion means oxidation transfers fuel carbon to products. Storage means carbon remains in a stated reservoir.

For the supplied mechanism problem, Carbon enters a leaf as carbon dioxide and later exits through respiration. Explain whether the carbon atom is used up. The atom is rearranged among molecules rather than destroyed. Photosynthesis incorporates carbon into organic molecules; respiration can return it as carbon dioxide. Energy transformations must be accounted for separately.

1. Read the supplied problem and mark the structures, processes or quantities named: Carbon enters a leaf as carbon dioxide and later exits through respiration. Explain whether the carbon atom is used up.
2. Draw the relevant boundary, pathway or comparison and label it using the scientific ideas above.
3. Write a causal explanation or calculation, showing how each observation supports the result.
4. Compare your reasoning with the worked solution; name a condition that would change or limit the inference.

Check your reasoning

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Take it further

New task: trace fuel carbon into combustion products, then into plant sugars in a supplied cycle. Expected: atoms move through different molecules; combustion and photosynthesis are distinct transfers, not atom creation.

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