Rainbow Waterways

Overview

In this 60-minute investigation, one Year 5 student predicts, observes and explains how coloured water moves through folded paper towels by capillary action. The lesson connects the rainbow effect to water transport in plants and the movement of water through human bodies, while developing fair-testing, observation and explanation skills.

Learning intentions

• WALT make and test a prediction about how water moves.
• WALT describe capillary action using evidence from an investigation.
• WALT identify variables that may affect the movement of water.
• WALT connect this investigation to water movement in plants and living things.

Success criteria

• I can draw and label the starting arrangement.
• I can record careful observations in words and pictures.
• I can explain that paper towels have tiny spaces that allow water to move through them.
• I can use evidence to describe how water moves upwards and across the paper towel, even against gravity.

Curriculum links

• Physical Science — Fluids, resistance, and buoyancy: testing predictions and explaining observed effects.
• Physical Science — Mass, volume, and density: making and testing predictions about materials and water.
• Physical Science — Fluids, resistance, and buoyancy: interpreting measurable changes through comparison.
• Science capability: investigating, gathering and interpreting evidence, and communicating explanations.

Lesson structure (60 minutes)

1. 0–7 min · Hook and prediction. Teacher displays a picture of a plant stem carrying water upwards and opens the hook and prediction slides. Ask: “How could water travel upwards when gravity pulls it down?” The student shares an initial idea, then predicts which empty glasses will contain coloured water after the experiment.

2. 7–15 min · Introduce the science. Teacher uses the capillary action teaching slides to explain that water can stick to the fibres in paper and to itself. Tiny spaces between the fibres draw water along and upwards; this movement is called capillary action. Clarify that the paper towel absorbs water and that the coloured dye makes the movement visible. The student labels a simple diagram with “water”, “paper towel”, “dye”, “gravity” and “capillary action”.

3. 15–25 min · Set up and predict. Place seven glasses in a straight line and add the same amount of water to glasses 1, 3, 5 and 7. Add a different food colouring or dye to each of these glasses so the colours form a rainbow sequence, such as red, yellow, blue and red/purple as available. Leave glasses 2, 4 and 6 empty. Fold six paper towels into long strips, then place one end in each coloured glass and the other end in the neighbouring empty glass. Use the rainbow investigation recording sheet for the student to record the arrangement, prediction and variables. Discuss controls: same type and length of towel, similar water volume, same glass size and the same observation time.

4. 25–40 min · Observe and record. Teacher starts a timer and invites the student to observe without disturbing the glasses. At five-minute intervals, the student records what has changed on the observation table using words, sketches or approximate height comparisons. Prompt: “Where is the water moving first? What evidence shows that the towel is wetting?” The student notes colour mixing as the coloured water reaches the empty glasses.

5. 40–50 min · Explain and connect. Teacher returns to the plant and body connection slides and discusses how capillary action helps water move through narrow tubes in plant stems. Introduce xylem as the plant tissue that carries water upwards, while explaining that plants also use transpiration—the loss of water vapour from leaves—which helps pull more water upwards. Connect carefully to the human body: blood vessels are tubes that carry water and dissolved substances, but blood is moved mainly by the heart, not by capillary action alone. The student compares the paper towel, a plant stem and a blood vessel, identifying one similarity and one difference.

6. 50–56 min · Review evidence. Teacher uses the discussion and explanation slides to ask: “Did the results match your prediction?”, “Which variables did we control?”, and “What might happen with thicker paper, less water or a longer gap?” The student gives a spoken explanation using the frame: “The water moved because… My evidence is… This is similar to…”.

7. 56–60 min · Plenary and exit response. The student completes the final question on the conclusion and exit response: “Explain how water travelled from a coloured glass into an empty glass.” Teacher photographs or retains the experiment and asks the student to state one new question for a future test.

Resources

• Seven clear glasses
• Water
• Food colouring or liquid dye in available rainbow colours
• Six paper towels
• Tray or waterproof mat
• Timer or classroom clock
• the rainbow waterways slide deck
• the rainbow investigation recording sheet
• Paper towels for spills
• Pencil and coloured pencils

Assessment

• Listen to the prediction and check whether it includes a reason based on an observable property or prior experience.
• Check the recording sheet for labelled diagrams, regular observations, controlled variables and comparisons between glasses.
• Use the final explanation to assess whether the student can describe capillary action and support the explanation with evidence from the investigation.

Differentiation

• Support the student with a labelled word bank, a partially completed diagram and sentence starters: “I notice…”, “I predict…”, and “The evidence shows…”.
• Because this is an individual investigation, allow the student to pause, revisit the setup and use photographs of each observation point rather than writing every detail.
• For EAL learners, demonstrate “absorb”, “move”, “upwards”, “fibre”, “gravity” and “capillary action” with gestures, labelled diagrams and repeated oral rehearsal.
• For an advanced learner, change one variable after the first result—such as paper-towel width or distance between glasses—and design a fair comparison, stating the independent, dependent and controlled variables.

Extension

• Investigate whether water moves faster through a single thick fold or a wider paper-towel strip. Keep the water volume, distance and observation time the same.
• Research and sketch how water moves from a plant’s roots to its leaves, including the role of xylem and transpiration.
• Compare the rainbow experiment with a celery stalk or white flower placed in coloured water, predicting where the dye will appear first.