Melting and Freezing

Active learning builds lasting understanding of melting and freezing by letting students feel the temperature changes and see materials transform. When students handle real substances and watch them shift between solid and liquid, the abstract concepts become concrete and memorable.

• 3rd Class
• Curious Investigators: Exploring Our World
• 4 activities
• 20 min–35 min

Learning Objectives

1. Describe the observable changes in a substance as it melts or freezes.
2. Compare the time it takes for different substances to melt under the same conditions.
3. Predict whether a given substance will melt or freeze at a specific temperature based on experimental data.
4. Explain that melting and freezing are reversible physical changes.

Inquiry Circle

⏱ 35 min·Small Groups

Melting Race: Small Groups

Provide small groups with ice, butter, and chocolate pieces. Students predict melting order in identical warm water bowls, then time each substance and record results on charts. Groups share findings and explain differences.

Prepare & details

Explain what happens to a substance when it melts or freezes.

Facilitation Tip: During Melting Race, set identical ice cube sizes and provide two timers so each group times its own melt at room temperature and in warm water.

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

⏱ 30 min·Pairs

Freezing Mixtures: Pairs

Pairs mix water with salt or sugar, predict freezing times in ice trays placed in freezer. Check after 20 minutes, observe differences, and discuss why pure water freezes faster. Extend by remelting samples.

Prepare & details

Compare the melting points of different materials.

Facilitation Tip: When pairs conduct Freezing Mixtures, ask them to record start times and temperatures to connect observations with measurable data.

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

⏱ 25 min·Whole Class

Temperature Prediction Walk: Whole Class

As a class, list classroom objects and predict if they melt or freeze at room temperature. Test select safe items like crayons or lotion, vote on outcomes, then verify with observations and class discussion.

Prepare & details

Predict whether a substance will melt or freeze at a given temperature.

Facilitation Tip: For Ice Cube Variables, give each student a recording sheet with columns for weight, shape, and temperature so they practice careful data collection.

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

Ice Cube Variables: Individual

Each student tests one ice cube in plain water, salt water, or under fan. Time melting, note conditions, and report to class. Compile data to identify fastest melt.

Prepare & details

Explain what happens to a substance when it melts or freezes.

Facilitation Tip: In Temperature Prediction Walk, pause at each station to ask students to justify their predictions using the word ‘temperature’ in a complete sentence.

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

Teachers approach melting and freezing by starting with familiar objects like ice and chocolate, then moving to careful measurements. Avoid rushing to explanations; instead, let students notice patterns and ask questions first. Research shows that hands-on repetition with different materials builds stronger conceptual change than lectures alone.

What to Expect

Students will confidently identify melting and freezing, explain that mass is conserved during these changes, and predict outcomes based on temperature differences. They will use accurate vocabulary and share clear observations with peers.

Watch Out for These Misconceptions

Common Misconception

During Ice Cube Variables, watch for students who believe the melted water has less mass than the ice cube.

What to Teach Instead

Ask students to weigh their ice cube before and after melting using a simple balance scale, then compare group results to confirm the mass stays the same.

Common Misconception

During Melting Race, watch for students who think chocolate and ice melt at the same speed because they are both solids.

What to Teach Instead

Have groups compare their timing data for ice and chocolate, then prompt them to explain why different materials melt at different rates.

Common Misconception

During Freezing Mixtures, watch for students who believe frozen wax cannot melt again.

What to Teach Instead

Let students melt the wax with gentle heat, then refreeze it, and ask them to describe how this shows freezing is reversible.

Assessment Ideas

Exit Ticket

After Ice Cube Variables, provide students with three cards labeled ‘Ice Cube,’ ‘Butter,’ and ‘Chocolate.’ Ask them to write one sentence for each predicting if it will melt in their hand and why, based on their observations.

Quick Check

During Temperature Prediction Walk, show students a video clip of ice melting in a warm room and water freezing in a freezer. Ask them to verbally identify the processes occurring and state one observation about how the substance changed.

Discussion Prompt

After Freezing Mixtures, pose the question: ‘If you put a cup of water outside on a very cold winter day, what do you think will happen to it? Will it melt or freeze? How do you know?’ Encourage students to use the terms melting, freezing, and temperature in their answers.

Extensions & Scaffolding

• Challenge: Ask students to design a container that keeps an ice cube frozen the longest and explain their choice to the class.
• Scaffolding: Provide labeled diagrams of thermometers and melting points to support students who struggle with recording temperature changes.
• Deeper exploration: Have students research the melting point of different metals and compare their uses in everyday items.

Key Vocabulary

Melting	The process where a solid changes into a liquid, usually when heated.
Freezing	The process where a liquid changes into a solid, usually when cooled.
Melting Point	The specific temperature at which a solid substance turns into a liquid.
Freezing Point	The specific temperature at which a liquid substance turns into a solid. For water, this is the same as the melting point.
Reversible Change	A change that can be undone, returning the substance to its original state.