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Science lesson plan · 10th grade (Year 11 in England) · 60 minutes

Rate of photosynthesis and limiting factors

Plants

CCSS NGSS.HS-LS1-5England: KS4 Combined Science: Photosynthesis

Objective and success criteria

Students will: Rate of photosynthesis and limiting factors.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Photosynthesis

Leads to: the next skill in this area.

Materials: Real plants or seeds, Hand lenses, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 6 min

  • Quick retrieval from earlier learning (Photosynthesis). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. What does chlorophyll do? (absorbs light energy / carries oxygen in blood / stores water / makes the cell wall) → absorbs light energyPrompt: It is the green pigment in leaves.
  2. Pondweed in light gives off 8 bubbles of oxygen in 2 minutes. What is the rate in bubbles per minute? → 4Prompt: Rate = amount ÷ time.
  3. Photosynthesis: which statement is NOT true? (Photosynthesis produces oxygen. / Chlorophyll is found in chloroplasts. / Glucose is made in the soil and taken up by roots. / Photosynthesis needs light.) → Glucose is made in the soil and taken up by roots.Prompt: Remember the word equation.

Hook · 6 min

  • 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.

I do: model it · 12 min

  • 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.

We do: guided practice · 12 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. On a graph, the rate rises with light intensity and then levels off. Why does it level off? (Light stops reaching the leaf / The plant has died / Another factor, such as CO₂ or temperature, is now limiting / Oxygen runs out) → Another factor, such as CO₂ or temperature, is now limitingPrompt: Adding more light no longer helps. Something else is in short supply.
  2. Light intensity is inversely proportional to the square of the distance from the lamp. A lamp is moved from 10 cm to 40 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?

You do: independent practice · 17 min

  • 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 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 7 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Light intensity is inversely proportional to the square of the distance from the lamp. A lamp is moved from 20 cm to 40 cm from a plant. The new light intensity is what fraction of the old one? Give a decimal. → 0.25Prompt: By what factor did the distance change?
  2. On a graph, the rate rises with light intensity and then levels off. Why does it level off? (Light stops reaching the leaf / Oxygen runs out / Another factor, such as CO₂ or temperature, is now limiting / The plant has died) → Another factor, such as CO₂ or temperature, is now limitingPrompt: Adding more light no longer helps. Something else is in short supply.

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Photosynthesis.
  • Use concrete materials: real plants or seeds.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

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

Free lesson plan from eurekami.com/lesson-plan-builder

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Rate of photosynthesis and limiting factors

Name

Date

Score/ 8

  1. Question 1

    Light intensity is inversely proportional to the square of the distance from the lamp. A lamp is moved from 10 cm to 20 cm from a plant. The new light intensity is what fraction of the old one? Give a decimal.

    Answer

  2. Question 2

    Why does the rate of photosynthesis fall at very high temperatures?

    • A. Chlorophyll becomes blue
    • B. Enzymes are denatured
    • C. Carbon dioxide turns into oxygen
    • D. There is too much light

  3. Question 3

    Bubbles per minute from pondweed at different lamp distances: 10 cm: 63 20 cm: 15.8 30 cm: 7 40 cm: 3.9 50 cm: 2.5 How many fewer bubbles per minute were counted at 30 cm than at 20 cm?

    Answer

  4. Question 4

    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.

    Answer

  5. Question 5

    On a graph, the rate rises with light intensity and then levels off. Why does it level off?

    • A. Oxygen runs out
    • B. Another factor, such as COâ‚‚ or temperature, is now limiting
    • C. Light stops reaching the leaf
    • D. The plant has died

  6. Question 6

    Bubbles per minute from pondweed at different lamp distances: 10 cm: 68 20 cm: 17 30 cm: 7.6 40 cm: 4.3 50 cm: 2.7 How many fewer bubbles per minute were counted at 30 cm than at 20 cm?

    Answer

  7. Question 7

    Light intensity is inversely proportional to the square of the distance from the lamp. A lamp is moved from 10 cm to 40 cm from a plant. The new light intensity is what fraction of the old one? Give a decimal.

    Answer

  8. Question 8

    Which of these is NOT a limiting factor for photosynthesis?

    • A. temperature
    • B. oxygen concentration
    • C. light intensity
    • D. carbon dioxide concentration

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Answer key: Rate of photosynthesis and limiting factors

  1. 1. 0.25

  2. 2. B. Enzymes are denatured

  3. 3. 8.8

  4. 4. 0.0625

  5. 5. B. Another factor, such as COâ‚‚ or temperature, is now limiting

  6. 6. 9.4

  7. 7. 0.0625

  8. 8. B. oxygen concentration