Science · 2nd Grade

Active learning ideas

Reversible Changes: Melting and Freezing

Active experiments let students feel the change in their hands, not just see it on paper. Because melting and freezing happen before their eyes, students grasp that the material stays the same even when its shape shifts. This sensory proof builds lasting understanding that many children miss when taught abstractly.

• Common Core State Standards
• 2-PS1-4

• 15–40 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Inquiry Circle
• 40 min · Pairs

Inquiry Circle: The Freezing Experiment

Pairs fill identical cups with the same amount of water, mark the water line with a marker, and place one cup in a freezer. When retrieved the next day, students compare the ice level to the original water line mark, weigh both cups on a balance, and discuss whether any water was lost or gained during the change.

Analyze why melting and freezing are considered reversible changes.

Facilitation Tip

During The Freezing Experiment, circulate with a small digital scale so every group weighs ice and then water in the same container before and after melting to confirm mass stays constant.

What to look for

Provide students with two pictures: one of ice melting and one of water freezing. Ask them to write one sentence explaining why each is a reversible change and one property that changes (e.g., shape, ability to flow).

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

Activity 02

• Think-Pair-Share
• 15 min · Pairs

Think-Pair-Share: Can We Undo It?

Show images of a melted candle (reversible), a cooked egg (irreversible), and a melted ice sculpture (reversible). Students categorize each with a partner and explain their reasoning, identifying what evidence would let them know whether a change can be undone.

Compare the properties of water in its liquid and solid states.

Facilitation Tip

During Can We Undo It?, listen for pairs who move beyond ‘yes or no’ to cite specific observations from their melting and freezing tests as proof.

What to look for

Show students a video clip of butter melting in a pan. Ask: 'Is this a reversible change? How do you know?' Have students give a thumbs up if they agree it's reversible and a thumbs down if they don't, then ask a few students to explain their reasoning.

• Understand
• Apply
• Analyze
• Self-Awareness
• Relationship Skills

Activity 03

• Gallery Walk
• 20 min · Individual

Gallery Walk: States of the Same Thing

Post photos of water in solid form (ice), liquid form (puddle), and gaseous form (steam from a kettle) at three stations. Students walk to each station and write one observation on a sticky note about what changed and one thing that stayed the same across all three forms.

Design an experiment to demonstrate a reversible change in a material.

Facilitation Tip

During the Gallery Walk, ask students to point to one photo caption that names a property that changed and one that stayed the same.

What to look for

Pose the question: 'Imagine you have a block of ice and a glass of water. What would you need to do to change the ice into water, and then change the water back into ice? What evidence shows that the water itself didn't change into something new?'

• Understand
• Apply
• Analyze
• Create
• Relationship Skills
• Social Awareness

A few notes on teaching this unit

Start with the senses: let students hold ice, then watch it melt in a clear cup on the overhead projector so the whole class sees the volume shrink but the mass stay the same. Avoid worksheets first; children need to feel the difference between reversible and irreversible changes before they label them. Research shows concrete experience beats abstract definitions for this age group.

By the end of the sequence, students will articulate that mass and type of matter are unchanged during melting and freezing, and they will use evidence from their own measurements to explain why. You’ll notice confident talk about conservation and reversible change in their writing and conversations.

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Watch Out for These Misconceptions

• During The Freezing Experiment, watch for students who believe the melted water has ‘disappeared’ or is ‘ruined.’

  Before students remove the ice from the scale, have them record the starting mass. After melting, place the same cup of water back on the scale so they see the identical reading and realize the material is still there.

• During The Freezing Experiment, watch for students who think freezing makes water lighter.

  Give each group two identical containers, one with liquid water and one with ice cubes of the same source. Let them weigh both on the same scale to confirm the readings match, then briefly discuss why ice floats because it is less dense without changing mass.

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Methods used in this brief

• Inquiry Circle
• Think-Pair-Share
• Gallery Walk