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

1. Complete the word equation: carbon dioxide + ___ → glucose + oxygen (oxygen / soil / water / glucose) → waterPrompt: The roots take this in.
2. Pondweed in light gives off 28 bubbles of oxygen in 4 minutes. What is the rate in bubbles per minute? → 7Prompt: Rate = amount ÷ time.
3. Photosynthesis: which statement is NOT true? (Photosynthesis needs light. / Photosynthesis produces oxygen. / Glucose is made in the soil and taken up by roots. / Photosynthesis takes in energy (it is endothermic).) → Glucose is made in the soil and taken up by roots.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. Farmers add paraffin heaters to greenhouses in winter. Which two factors does this increase? (temperature and carbon dioxide / light and oxygen / water and oxygen / light and water) → temperature and carbon dioxidePrompt: Burning a fuel gives out heat and a gas.
2. Light intensity is inversely proportional to the square of the distance from the lamp. A lamp is moved from 10 cm to 30 cm from a plant. The new light intensity is what fraction of the old one? Give a decimal. → 0.1111Prompt: 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 / Light stops reaching the leaf / The plant has died / Another factor, such as CO₂ or temperature, is now limiting) → 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: 50 20 cm: 12.5 30 cm: 5.6 40 cm: 3.1 50 cm: 2 How many fewer bubbles per minute were counted at 40 cm than at 30 cm? → 2.5Prompt: Read both values from the table.

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