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What do plants need to make food? Investigating photosynthesis

By OtisamLMS · 21 Oct 2026

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Subject
Integrated Science · SHS
Year
SHS 1
Week
Term 1 · Week 6
Lessons
2 × 80 min
Class size
40
Strand
Systems
Sub-strand
Plant nutrition
Content standard
Learners explain how green plants make their own food and investigate the conditions it needs.
Key words
chlorophyllstarchglucosecarbon dioxidefair testvariablecontrol

Learning indicators

  • State the raw materials and products of photosynthesis
  • Carry out a fair test to show that light is needed for starch to form in a leaf
  • Write the word equation for photosynthesis

Core competencies

  • Critical thinking and problem solving
  • Collaboration
  • Digital literacy (recording results in a table)

Resources

  • A potted plant kept in the dark for two days, and one kept in sunlight
  • Aluminium foil or black paper, paper clips
  • Iodine solution, ethanol, hot water in a flask, white tiles
  • Safety goggles

Lesson flow

  1. 1Starter

    Hold up a mango and ask: where did all this mass come from? The soil? The water? Learners vote with a show of hands, then hear that a large tree takes very little from the soil. Leave the question open; the lesson will answer it.

  2. 2Main activities

    1. Revise the starch test with iodine on a slice of yam or cassava: blue-black means starch is present. 2. Explain the plan: cover part of one leaf on the sunlit plant with foil the day before (done in advance) and compare it with an uncovered part. 3. Groups follow the leaf-testing steps on the card: boil the leaf briefly in water, soften it in warm ethanol (no flames near the ethanol), rinse, then add iodine. The teacher demonstrates the ethanol step first. 4. Groups record the colour of the covered and uncovered parts, and the leaf from the dark plant, in a results table. 5. Discussion: which part is the control? What was the one variable changed? Build the word equation on the board from what learners say: carbon dioxide + water → (light, chlorophyll) → glucose + oxygen.

  3. 3Reflection

    Return to the mango. Each group writes a two-line answer to 'Where did the mass come from?' using the words carbon dioxide and glucose, and one group reads theirs out.

Assessment

Short quiz: label the inputs and outputs of photosynthesis on a leaf diagram; explain why the covered part stayed brown with iodine; name one thing that made the test fair.

Differentiation

Support: give a partly completed results table and word equation with gaps. Extension: plan a test to show that carbon dioxide is needed, naming the control and the variable.

Homework

Write a paragraph explaining to a farmer why leaves should not be removed from young maize plants.

Teacher notes

Prepare the dark plant two days ahead. Keep ethanol well away from any flame; warm it in a beaker standing in hot water from a flask.
Integrated Science practice questions Video lessons

Plans are written by OtisamLMS teachers and are a starting point: adapt them to your learners. Report a problem with this plan.