Water, Light, Leaf Fuel

Overview

Students investigate the striking movement of whiteboard marker ink on water, then connect the movement of water to what plants need for photosynthesis. They build and explain a simple model showing how leaves use light, water and carbon dioxide to make glucose, which can be stored as starch or used to build plant structures.

Learning intentions

• WALT describe photosynthesis as a process that makes glucose.
• WALT identify light, water and carbon dioxide as the requirements for photosynthesis.
• WALT explain how leaf structures help photosynthesis happen.
• WALT communicate a scientific explanation using observations and a labelled model.

Success criteria

• I can state what photosynthesis makes and name its three requirements.
• I can describe what I observed when marker ink met water.
• I can explain that water is transported to leaves, where it is used in photosynthesis.
• I can use arrows and labels to show inputs and outputs in a photosynthesis model.

Curriculum links

• Biological Science — plants use light, water and carbon dioxide to make glucose through photosynthesis.
• Biological Science — leaves are thin and contain chloroplasts that capture light.
• Biological Science — sugars made in photosynthesis may be stored as starch or used to build cellulose.
• Biological Science — students investigate, record observations and communicate findings using evidence.

Lesson structure (45 minutes)

1. 0–5 min · Phenomenon hook. Teacher places a small amount of water on a white plate, writes a simple symbol with a whiteboard marker, then gently tilts the plate so the writing lifts and moves; students silently observe and record “I notice…” and “I wonder…” on the observation and explanation worksheet. Ask: “Where has the writing gone, and what might be moving?” Do not suggest that this demonstration is photosynthesis; explain that it is a model for noticing how substances can move when water is present.

2. 5–10 min · Share and connect. Teacher collects several observations and introduces the question, “How does water get to a leaf, and what does the leaf do with it?” Open the hook and guiding-question slides. Students pair-share an initial explanation, then identify what evidence came from the demonstration and what is still a prediction.

3. 10–18 min · Direct teaching. Teacher uses the photosynthesis explanation slides to teach that photosynthesis uses light energy, water and carbon dioxide to make glucose; oxygen is also produced. Show a simple equation using words rather than chemical symbols. Students complete the first section of the photosynthesis inputs-and-outputs table and answer: “Which input comes from the air? Which input must be transported from the roots?”

4. 18–28 min · Build a leaf model. Teacher displays a large leaf diagram from the leaf structure and process slides and models arrows for sunlight, carbon dioxide entering through tiny openings, water arriving through veins, glucose leaving or being stored, and oxygen leaving. Explain that chloroplasts capture light and that a thin leaf helps materials move short distances. In pairs, students complete and label the model on the leaf diagram task, adding arrows and a short note about chloroplasts. Circulate and ask, “What is the evidence that this is an input or output?”

5. 28–37 min · Apply and explain. Teacher presents three situations on the application-question slides: a plant kept in darkness, a leaf covered so it receives little light, and a plant receiving no water. Model one response using the structure “If…, then…, because…”. Students choose two situations and write predictions on the worksheet. They must use at least two terms accurately: light, water, carbon dioxide, glucose, oxygen, chloroplast or starch. Partners compare answers and improve one explanation.

6. 37–43 min · Plenary discussion. Teacher returns to the plate demonstration using the comparison and misconception-check slide. Clarify that the ink movement is not photosynthesis and is not proof that plants make food; it is a useful starting observation about movement in water. Students answer: “How is the demonstration similar to, and different from, water reaching a leaf?” Invite two pairs to share, emphasising that scientific models show some features but not every detail.

7. 43–45 min · Exit check. Teacher displays the three-question exit prompt on the exit-ticket slide. Students complete the final box on the exit response section independently before handing it in.

Resources

• Whiteboard marker pen
• White plate
• Water and a tray or cloth for spills
• the photosynthesis and demonstration deck
• the observation, modelling and explanation worksheet
• Projector or interactive display
• Spare pencils and coloured pencils
• Paper towels

Assessment

• Listen to paired explanations during the hook and check whether students distinguish an observation from a prediction.
• During the model task, check that students identify light, water and carbon dioxide as inputs and glucose and oxygen as products.
• Exit response: students state what photosynthesis makes, name two requirements, and explain one way a leaf is adapted for the process.

Differentiation

• Provide a word bank, partially completed arrows and the sentence frame “Photosynthesis needs ___ and ___; it makes ___ because ___” for students needing support.
• Use a labelled oral rehearsal before writing; allow students to explain their model verbally or draw first. Pair EAL learners with supportive peers and pre-teach the meanings of input, output, transported and stored.
• For students requiring additional sensory or motor support, provide a larger diagram, thicker pencils and a clear view of the demonstration. Do not require students to handle the plate.
• Extend confident students by asking them to explain why a plant can store glucose as starch and how that stored material might support growth.