Young Explorers: Investigating Our World · 2nd Class

Active learning ideas

Thermal Changes: Melting and Freezing

Active learning helps students grasp thermal changes by engaging with real materials they already recognize, like ice and chocolate. Hands-on experiences let them connect abstract ideas about heat and particles to visible, concrete observations, which builds durable understanding.

• NCCA Curriculum Specifications
• NCCA: Science - Materials - Changing States
• NCCA: Science - Energy and Forces - Heat Transfer

• 15–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Stations Rotation
• 45 min · Small Groups

Stations Rotation: Melting Comparisons

Prepare stations with ice, butter, and chocolate in identical conditions: room temperature, warm water, sunlight. Groups rotate every 10 minutes, timing melts and recording factors like surface area. Discuss which melts fastest and why.

Explain how adding or removing thermal energy affects the state of matter.

Facilitation Tip

During Station Rotation: Melting Comparisons, place identical amounts of each substance on plates so students compare melting rates under the same conditions.

What to look for

Provide students with a small cup of water and a freezer. Ask them to predict how long it will take for the water to freeze. After a set time, have them observe the results and explain whether their prediction was accurate and why.

• Remember
• Understand
• Apply
• Analyze
• Self-Management
• Relationship Skills

Activity 02

• Experiential Learning
• 20 min · Pairs

Prediction Pairs: Freezing Salt Test

Pairs fill trays with water, some plain and some salted, then place in freezer. Predict and time freezing. After 24 hours, measure ice thickness and compare results, noting salt's effect.

Compare the melting points of different substances.

Facilitation Tip

For Prediction Pairs: Freezing Salt Test, have partners share their predictions before adding salt to water to encourage reasoning and discussion.

What to look for

Present students with three identical containers, one with ice, one with butter, and one with chocolate, placed in a warm spot. Ask: 'Which item do you think will melt first? Why? What do you observe happening to each item over the next 15 minutes?' Record observations and discuss the different melting rates.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Activity 03

• Experiential Learning
• 30 min · Whole Class

Whole Class: Thermal Energy Demo

Use a large ice block; students suggest ways to melt it faster (rub hands, blow air, add salt). Vote on predictions, test one by one, and chart temperature changes with a thermometer.

Predict how impurities might affect the freezing point of water.

Facilitation Tip

In the Whole Class: Thermal Energy Demo, use a thermometer to measure temperature changes so students connect numerical data to their observations.

What to look for

Give each student a card with a picture of an ice cube melting. Ask them to write two sentences: one explaining what is happening to the ice cube, and one explaining what needs to happen for the water to turn back into ice.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Activity 04

• Experiential Learning
• 15 min · Individual

Individual Journals: Home Link

Students draw and describe an object melting or freezing at home, predict time needed, test, and journal results. Share findings next class to spot patterns.

Explain how adding or removing thermal energy affects the state of matter.

Facilitation Tip

For Individual Journals: Home Link, ask students to sketch their observations and write simple captions using science vocabulary.

What to look for

Provide students with a small cup of water and a freezer. Ask them to predict how long it will take for the water to freeze. After a set time, have them observe the results and explain whether their prediction was accurate and why.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

A few notes on teaching this unit

Teachers should emphasize the reversibility of melting and freezing by having students refreeze melted substances during activities. Avoid focusing only on vocabulary; instead, link the words ‘melting,’ ‘freezing,’ and ‘temperature’ directly to what students see and feel. Research shows that engaging multiple senses and repeating observations over time strengthens conceptual memory.

Successful learning shows when students can explain why some items melt faster than others and predict what happens to substances when heat is added or removed. They should use evidence from their investigations to describe melting and freezing as reversible, physical changes.

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Watch Out for These Misconceptions

• During Station Rotation: Melting Comparisons, watch for students who believe melted substances become new materials. Redirect them by asking, ‘What happens if you cool the melted chocolate or butter again?’, guiding them to observe refreezing.

  During Station Rotation: Melting Comparisons, have students record the mass of the substance before melting and after refreezing to show that no mass is lost, reinforcing that it is a physical change.

• During Station Rotation: Melting Comparisons, watch for students who assume all solids melt at the same temperature. Ask them to note the order in which items soften and compare their melting times.

  During Station Rotation: Melting Comparisons, provide a simple chart for students to fill in with the time each substance starts to melt, helping them see that different materials have different melting points.

• During Prediction Pairs: Freezing Salt Test, listen for students who say freezing only happens in very cold places. Remind them that their classroom freezer and ice cream makers work at much warmer temperatures because salt lowers water’s freezing point.

  During Prediction Pairs: Freezing Salt Test, have students measure and compare the freezing times of plain and salted water to connect the activity to real-world examples like icy roads.

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Methods used in this brief

• Stations Rotation
• Experiential Learning