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Science lesson plan · 9th grade (Year 10 in England) · 60 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 · 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? (stores water / makes the cell wall / carries oxygen in blood / absorbs light energy) → absorbs light energyPrompt: It is the green pigment in leaves.
  2. Pondweed in light gives off 20 bubbles of oxygen in 2 minutes. What is the rate in bubbles per minute? → 10Prompt: Rate = amount ÷ time.
  3. Photosynthesis: which statement is NOT true? (Photosynthesis takes in energy (it is endothermic). / Photosynthesis produces oxygen. / Chlorophyll is found in chloroplasts. / Glucose is made in the soil and taken up by roots.) → 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: Photosynthesis: word and balanced symbol equations. 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 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 · 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. Which is the balanced symbol equation for photosynthesis? (6CO₂ + 6H₂O → C₆H₁₂O₆ + 3O₂ / 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ / C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O / CO₂ + H₂O → C₆H₁₂O₆ + O₂) → 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂Prompt: Carbon dioxide and water are the reactants.
  2. A leaf makes 2 molecules of glucose by photosynthesis. Using 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, how many water molecules are used? → 12Prompt: Read the numbers in front of each formula.

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. Which is the balanced symbol equation for photosynthesis? (6O₂ + 6H₂O → C₆H₁₂O₆ + 6CO₂ / 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ / 6CO₂ + 6H₂O → C₆H₁₂O₆ + 3O₂ / C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O) → 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂Prompt: Carbon dioxide and water are the reactants.
  2. A leaf makes 2 molecules of glucose by photosynthesis. Using 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, how many oxygen molecules are released? → 12Prompt: Read the numbers in front of each formula.

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/ 8

  1. Question 1

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

  3. Question 3

    Is photosynthesis exothermic or endothermic?

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

  4. Question 4

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

    Answer

  5. Question 5

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

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

  6. Question 6

    A leaf makes 3 molecules of glucose by photosynthesis. Using 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, how many carbon dioxide molecules are used?

    Answer

  7. Question 7

    Plants turn some glucose into cellulose. What is the cellulose used for?

    • A. storing energy for winter
    • B. absorbing light
    • C. making proteins
    • D. strengthening cell walls

  8. Question 8

    Which substance in chloroplasts absorbs the light?

    • A. chlorophyll
    • B. cellulose
    • C. starch
    • D. glucose

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Answer key: Photosynthesis: word and balanced symbol equations

  1. 1. 18

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

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

  4. 4. 30

  5. 5. C. water molecules that are split

  6. 6. 18

  7. 7. D. strengthening cell walls

  8. 8. A. chlorophyll