Science · Grade 3

Active learning ideas

Melting and Freezing

Active learning works so well for melting and freezing because these processes happen all around us every day. When students manipulate ice, salt, and water in real time, they connect abstract concepts to tangible experiences. Hands-on experiments make the reversibility of state changes visible and memorable.

• Ontario Curriculum Expectations
• 2-PS1-4

• 25–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Outdoor Investigation Session
• 30 min · Small Groups

Observation Lab: Ice Melting Conditions

Provide ice cubes in four setups: room temperature bowl, warm water, shaded spot, and sunny spot. Students time melting rates, measure water volume changes, and record temperature every 5 minutes. Discuss which condition melts fastest and why.

Explain what causes a solid to melt and a liquid to freeze.

Facilitation Tip

During Observation Lab: Ice Melting Conditions, have students rotate roles every 3 minutes to keep engagement high and ensure everyone participates.

What to look for

Provide students with a small cup of ice cubes and a warm lamp. Ask them to observe and record two changes they see. Then, ask them to write one sentence explaining what caused the ice to change and one sentence describing how they could reverse the change.

• Remember
• Understand
• Analyze
• Social Awareness
• Self-Awareness
• Decision-Making

Activity 02

• Outdoor Investigation Session
• 25 min · Whole Class

Demo: Salt on Ice

Place ice cubes on plates; sprinkle salt on half. Students observe faster melting on salted ice, touch to feel temperature drop, and hypothesize about salt's effect on freezing point. Repeat with water freezing tests.

Compare the energy changes involved in melting versus freezing.

Facilitation Tip

For Demo: Salt on Ice, use a document camera so students can see the ice crack and water form in real time.

What to look for

Pose the question: 'Imagine you have a glass of water and a block of ice. What needs to happen to the ice for it to become water, and what needs to happen to the water for it to become ice? What is the same about these two processes, and what is different?' Facilitate a class discussion focusing on energy transfer and reversibility.

• Remember
• Understand
• Analyze
• Social Awareness
• Self-Awareness
• Decision-Making

Activity 03

• Outdoor Investigation Session
• 45 min · Pairs

Pairs Experiment: Freezing Salt Water

Pairs mix varying salt amounts in water cups, place in freezer overnight, then check and measure ice thickness next day. Predict and compare results, noting less ice forms in saltier solutions.

Predict how different substances might melt or freeze at varying temperatures.

Facilitation Tip

In Pairs Experiment: Freezing Salt Water, remind students to use the same size container and mark starting volumes with tape for fair comparisons.

What to look for

Show students pictures of different scenarios: a puddle drying up, frost on a window, a popsicle melting, water turning to ice in a freezer. Ask students to label each picture with either 'Melting' or 'Freezing' and briefly explain their choice.

• Remember
• Understand
• Analyze
• Social Awareness
• Self-Awareness
• Decision-Making

Activity 04

• Outdoor Investigation Session
• 35 min · Small Groups

Prediction Challenge: Substance Melts

Show butter, chocolate, and crayons at room temperature. Students predict melting order, heat gently, and time each. Chart results and revise predictions based on observations.

Explain what causes a solid to melt and a liquid to freeze.

Facilitation Tip

In Prediction Challenge: Substance Melts, require students to justify their predictions with evidence from prior activities to build reasoning skills.

What to look for

Provide students with a small cup of ice cubes and a warm lamp. Ask them to observe and record two changes they see. Then, ask them to write one sentence explaining what caused the ice to change and one sentence describing how they could reverse the change.

• Remember
• Understand
• Analyze
• Social Awareness
• Self-Awareness
• Decision-Making

A few notes on teaching this unit

Teachers should focus on helping students notice patterns rather than memorizing definitions. Start with familiar examples like popsicles melting before introducing formal terms like melting point. Encourage students to predict outcomes, test ideas, and revise thinking based on evidence. Avoid rushing to conclusions; let students struggle productively with the data before providing answers.

Students will confidently identify the conditions needed for melting and freezing, and explain why these changes are reversible. They will record observations accurately and discuss how energy transfer affects matter. Group work will show clear collaboration and shared understanding.

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Watch Out for These Misconceptions

• During Observation Lab: Ice Melting Conditions, watch for students who describe melting as a chemical change because 'it looks different'.

  After students melt ice and refreeze it, ask them to compare the starting and ending substances. Have them note that it is still water, just in a different state, to reinforce that it is a physical change.

• During Prediction Challenge: Substance Melts, watch for students who assume all substances melt at the same temperature.

  During the activity, have students compare their melting times for different substances. Ask them to discuss why some melted faster than others and connect this to the idea of individual melting points.

• During Pairs Experiment: Freezing Salt Water, watch for students who expect the frozen salt water to shrink in volume.

  Before freezing, have students measure and mark the starting volume on their containers. After freezing, ask them to compare the volume to their starting point and discuss why salt water expands differently than pure water.

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Methods used in this brief

• Outdoor Investigation Session