• Quick retrieval from earlier learning (Photosynthesis). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. In which part of a plant cell does photosynthesis happen? (chloroplasts / nucleus / vacuole / cell wall) → chloroplastsPrompt: This part contains the green pigment.
2. Pondweed in light gives off 14 bubbles of oxygen in 2 minutes. What is the rate in bubbles per minute? → 7Prompt: Rate = amount ÷ time.
3. Photosynthesis: which statement is NOT true? (Photosynthesis turns oxygen into carbon dioxide. / Photosynthesis needs light. / Photosynthesis takes in energy (it is endothermic). / Photosynthesis produces oxygen.) → Photosynthesis turns oxygen into carbon dioxide.Prompt: Remember the word equation.

• Bring in a plant that has been kept in the dark next to one in the light, and ask what happened.
• Share the objective: Rate of photosynthesis and limiting factors. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Which of these is NOT a limiting factor for photosynthesis?
• Step 1: The main limiting factors are light intensity, carbon dioxide concentration and temperature.
• Step 2: So the answer is: oxygen concentration
• Answer: oxygen concentration
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. Why does the rate of photosynthesis fall at very high temperatures? (Enzymes are denatured / There is too much light / Carbon dioxide turns into oxygen / Chlorophyll becomes blue) → Enzymes are denaturedPrompt: Photosynthesis is controlled by proteins that change shape when too hot.
2. Light intensity is inversely proportional to the square of the distance from the lamp. A lamp is moved from 20 cm to 80 cm from a plant. The new light intensity is what fraction of the old one? Give a decimal. → 0.0625Prompt: By what factor did the distance change?

• Students work on the student sheet. Circulate and check the first two answers of every student early.
• Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. On a graph, the rate rises with light intensity and then levels off. Why does it level off? (Oxygen runs out / Another factor, such as CO₂ or temperature, is now limiting / The plant has died / Light stops reaching the leaf) → Another factor, such as CO₂ or temperature, is now limitingPrompt: Adding more light no longer helps. Something else is in short supply.
2. Bubbles per minute from pondweed at different lamp distances: 10 cm: 53 20 cm: 13.3 30 cm: 5.9 40 cm: 3.3 50 cm: 2.1 How many fewer bubbles per minute were counted at 40 cm than at 30 cm? → 2.6Prompt: Read both values from the table.

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-10.