1. Which gas do plants take in during photosynthesis?
- Answer:
- B — Carbon dioxide
- Model:
- Carbon dioxide.
- Guidance:
- One mark for B. No mark for a correct letter with a contradictory reason.
Multiple choice
1 mark
Remember
2. Complete the word equation: carbon dioxide + ____________ → glucose + ____________
- Answer:
- water; oxygen
- Model:
- carbon dioxide + water → glucose + oxygen
- Marks:
- 1 mark for water; 1 mark for oxygen
- Guidance:
- Accept 'H2O' for water and 'O2' for oxygen. Do not accept 'sunlight' in either blank — light is a condition, not a reactant.
Fill in the blank
2 marks
Remember
3. Explain why a plant kept in complete darkness for a week cannot make glucose.
- Model:
- Chlorophyll absorbs light energy, and that energy is what drives the reaction that joins carbon dioxide and water into glucose. With no light there is no energy for the reaction, so no glucose is made.
- Marks:
- 1 mark for identifying that light is required; 1 mark for linking chlorophyll to absorbing light energy; 1 mark for explaining that without that energy the reaction cannot proceed
- Guidance:
- Look for the causal chain, not the keywords. A response that names chlorophyll but never links light to energy scores 1.
Short answer
3 marks
Understand
4. Using the results in the table, describe what happens to the rate of photosynthesis as light intensity increases, and suggest why the rate stops rising after 60%.
- Model:
- The rate rises steadily from 8 to 26 bubbles per minute as light intensity increases from 20% to 60%. After 60% the rate levels off at about 26–27 bubbles per minute. This suggests light is no longer the limiting factor — something else, such as carbon dioxide concentration or temperature, is now limiting the rate.
- Marks:
- 1 mark for describing the increase; 1 mark for quoting supporting figures from the table; 1 mark for identifying that the rate plateaus; 1 mark for naming another limiting factor
- Guidance:
- Award the data marks for quoting figures from the table, not for describing the shape in words alone. The final mark needs a named alternative limiting factor.
Data interpretation
4 marks
Analyse