Reversible Changes

Active learning works well for reversible changes because students need to see and feel physical processes to grasp the concept fully. Watching ice melt and refreeze or dissolving sugar then evaporating it helps students move from abstract ideas to concrete evidence they can observe and discuss.

• Year 5
• Science
• 4 activities
• 20 min–45 min

Learning Objectives

1. Classify changes as reversible or irreversible based on experimental evidence.
2. Compare and contrast the processes of melting and dissolving, identifying similarities in their reversibility.
3. Predict whether a given change, such as heating chocolate or mixing sand with water, is reversible and justify the prediction with scientific reasoning.
4. Explain the indicators that signal a change is reversible, such as the ability to recover the original substance.
5. Demonstrate the recovery of a dissolved substance (e.g., salt or sugar) from a solution through evaporation.

Inquiry Circle

⏱ 30 min·Pairs

Pairs Test: Melting and Freezing

Pairs heat ice cubes in warm water, record temperature changes, then place in freezer to refreeze. They measure mass before and after to check conservation. Discuss if the ice returns to original form.

Prepare & details

Explain how we know if a change is reversible.

Facilitation Tip: During the Pairs Test: Melting and Freezing, circulate and ask each pair to explain why the ice’s change is reversible using their observations of state and temperature.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Inquiry Circle

⏱ 45 min·Small Groups

Small Groups: Dissolving Challenge

Groups dissolve salt in warm water, stir, then evaporate using heat lamps or sun. Filter if needed and weigh recovered salt. Compare with undissolved sample to confirm reversibility.

Prepare & details

Compare the processes of melting ice and dissolving sugar, identifying similarities.

Facilitation Tip: In the Small Groups: Dissolving Challenge, provide measuring spoons for both before and after dissolving to directly address the misconception that dissolving destroys the solute.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Inquiry Circle

⏱ 35 min·Whole Class

Whole Class: Prediction Relay

Display materials like paper, clay, ink. Class predicts reversibility in teams, tests one by one: fold/unfold paper, mould/remould clay. Vote and justify after each trial.

Prepare & details

Predict the reversibility of various changes and justify your predictions.

Facilitation Tip: For the Whole Class: Prediction Relay, have students justify their predictions using evidence from prior activities to reinforce connections between ideas.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Inquiry Circle

⏱ 20 min·Individual

Individual: Home Link Observation

Students select household item, test reversible change like butter melting, record steps and photos. Share findings next lesson to build class examples database.

Prepare & details

Explain how we know if a change is reversible.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

• Analyze
• Evaluate
• Create
• Self-Management
• Self-Awareness

Teaching This Topic

Teaching reversible changes effectively starts with hands-on experiments that let students test ideas themselves. Avoid lecturing about state changes; instead, guide them to observe and explain. Research shows students learn best when they connect their prior knowledge to new evidence through discussion and reflection.

What to Expect

Successful learning looks like students confidently explaining why some changes can be reversed while others cannot. They should use evidence from their experiments to support their answers and correct peers’ misconceptions during group discussions.

Watch Out for These Misconceptions

Common Misconception

During Small Groups: Dissolving Challenge, watch for students who believe the sugar disappears forever.

What to Teach Instead

Have students weigh the sugar before dissolving and after evaporation to show the mass remains the same, using measuring spoons and a simple balance.

Common Misconception

During Whole Class: Prediction Relay, watch for students who assume all heating causes reversible changes.

What to Teach Instead

Use the relay stations to test multiple materials like chocolate, bread, and ice, and have students classify outcomes based on whether the substance remains unchanged.

Common Misconception

During Pairs Test: Melting and Freezing, watch for students who think mixing sand and water is irreversible like baking a cake.

What to Teach Instead

Provide filter paper and funnels so students can separate the sand and water, demonstrating that the substances can be recovered unchanged.

Assessment Ideas

Quick Check

After Pairs Test: Melting and Freezing and Small Groups: Dissolving Challenge, present students with a list of changes such as freezing water, mixing flour and water, boiling an egg, and dissolving salt. Ask them to circle reversible changes and explain two of their choices.

Discussion Prompt

During Whole Class: Prediction Relay, pose the question: 'Imagine you dissolve sugar in water, then boil the solution. How do you know the sugar is still there? How could you prove it?' Facilitate a discussion connecting dissolving, evaporation, and the return of the original substance.

Exit Ticket

After Individual: Home Link Observation, give each student a small card to write one reversible change they tested and one irreversible change they observed. For the reversible change, they should explain how it could be undone, using evidence from their activity.

Extensions & Scaffolding

• Challenge students to design an experiment to reverse a change they haven’t tested, such as melting butter or freezing juice.
• Scaffolding: Provide labeled diagrams of filtering equipment for students struggling with the idea of reversible mixtures like sand and water.
• Deeper exploration: Ask students to research and present one real-world example of a reversible change in industry or nature.

Key Vocabulary

Reversible Change	A change where the original substance can be obtained again, often by reversing the process that caused the change.
Irreversible Change	A change where the original substance cannot be easily obtained again, as a new substance has been formed.
Melting	The process where a solid turns into a liquid due to an increase in temperature. This is a reversible change.
Dissolving	The process where a solute spreads evenly into a solvent to form a solution. The solute can often be recovered by evaporating the solvent.
Evaporation	The process where a liquid turns into a gas or vapor, often due to heating. This can be used to recover dissolved solids.