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Science lesson plan · 9th grade (Year 10 in England) · 30 minutes

Photosynthesis: word and balanced symbol equations

Plants

CCSS NGSS.HS-LS1-5England: GCSE Combined Science: Bioenergetics

Objective and success criteria

Students will: Photosynthesis: word and balanced symbol equations.

  • 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: Aerobic and anaerobic respiration equations compared; Light-dependent reactions and the Calvin cycle

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

Warm-up · 4 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. Complete the word equation: carbon dioxide + ___ → glucose + oxygen (soil / water / oxygen / 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 takes in energy (it is endothermic). / Photosynthesis produces oxygen. / Photosynthesis needs light. / Plants only respire at night.) → Plants only respire at night.Prompt: Remember the word equation.

Hook · 3 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: Photosynthesis: word and balanced symbol equations. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Which is the balanced symbol equation for photosynthesis?
  • Step 1: carbon dioxide + water → glucose + oxygen (light energy, chlorophyll)
  • Step 2: Left: 6 C, 12 H, 18 O. Right: 6 C, 12 H, 18 O.
  • Step 3: So the answer is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
  • Answer: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 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. Which is the balanced symbol equation for photosynthesis? (6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ / CO₂ + H₂O → C₆H₁₂O₆ + O₂ / 6CO₂ + 6H₂O → C₆H₁₂O₆ + 3O₂ / 6O₂ + 6H₂O → C₆H₁₂O₆ + 6CO₂) → 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂Prompt: Carbon dioxide and water are the reactants.
  2. A leaf makes 4 molecules of glucose by photosynthesis. Using 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, how many oxygen molecules are released? → 24Prompt: Read the numbers in front of each formula.

You do: independent practice · 7 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 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. In photosynthesis, where does the oxygen gas released come from? (glucose / nitrogen in the air / water molecules that are split / the soil) → water molecules that are splitPrompt: Experiments with labelled oxygen atoms showed this.
  2. Which is the balanced symbol equation for photosynthesis? (6O₂ + 6H₂O → C₆H₁₂O₆ + 6CO₂ / 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ / C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O / CO₂ + H₂O → C₆H₁₂O₆ + O₂) → 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂Prompt: Carbon dioxide and water are the reactants.

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

  • Move on to: Aerobic and anaerobic respiration equations compared; Light-dependent reactions and the Calvin cycle.
  • 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-9.

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

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Photosynthesis: word and balanced symbol equations

Name

Date

Score/ 6

  1. Question 1

    A leaf makes 5 molecules of glucose by photosynthesis. Using 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, how many water molecules are used?

    Answer

  2. Question 2

    Which is the balanced symbol equation for photosynthesis?

    • A. 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
    • B. CO₂ + H₂O → C₆H₁₂O₆ + O₂
    • C. C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
    • D. 6CO₂ + 6H₂O → C₆H₁₂O₆ + 3O₂

  3. Question 3

    Is photosynthesis exothermic or endothermic?

    • A. endothermic: energy is transferred from light to the chemical store in glucose
    • B. neither
    • C. exothermic: it releases oxygen
    • D. exothermic: it releases heat

  4. Question 4

    A leaf makes 2 molecules of glucose by photosynthesis. Using 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, how many water molecules are used?

    Answer

  5. Question 5

    In photosynthesis, where does the oxygen gas released come from?

    • A. water molecules that are split
    • B. nitrogen in the air
    • C. the soil
    • D. glucose

  6. Question 6

    A leaf makes 4 molecules of glucose by photosynthesis. Using 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, how many water molecules are used?

    Answer

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Answer key: Photosynthesis: word and balanced symbol equations

  1. 1. 30

  2. 2. A. 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

  3. 3. A. endothermic: energy is transferred from light to the chemical store in glucose

  4. 4. 12

  5. 5. A. water molecules that are split

  6. 6. 24