Foundations of Matter and Chemical Change · 5th Year

Active learning ideas

Changes of State: Melting and Freezing

Active learning helps students visualize particle motion during melting and freezing, which is invisible at the macroscopic level. Hands-on stations and investigations build evidence about how energy changes affect states of matter, making abstract concepts concrete and memorable for young scientists.

• NCCA Curriculum Specifications
• NCCA: Primary - Materials - Change of State

• 20–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Stations Rotation
• 35 min · Small Groups

Stations Rotation: Melting Challenges

Set up stations with ice cubes: one at room temperature, one in warm water, one with salt sprinkled on top, and one wrapped in cloth. Small groups rotate every 7 minutes, timing melts and noting temperatures. Groups share data to compare effects.

What happens to ice when it gets warm?

Facilitation Tip

During Station Rotation: Melting Challenges, circulate with a timer to ensure students rotate every 8 minutes so they experience multiple materials and temperature probes.

What to look for

Provide students with two beakers, one containing ice cubes and the other containing liquid water at room temperature. Ask them to write one sentence describing what will happen to the ice cubes if left out and one sentence describing what will happen to the liquid water if placed in a freezer, referencing particle movement.

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

Activity 02

• 45 min · Pairs

Freezing Point Investigation

Pairs fill trays with water samples: pure water, saltwater, and sugared water. Place in freezer and check hourly, recording first ice formation times. Discuss why impurities affect freezing points using particle explanations.

How can we turn water back into ice?

Facilitation Tip

For Freezing Point Investigation, remind students to record temperatures every 30 seconds to capture the plateau at 0°C clearly on their graphs.

What to look for

Display a graph showing the temperature of a substance over time as it melts and then freezes. Ask students to identify the melting point and freezing point on the graph and explain what is happening to the particles at each of these points.

Activity 03

• 25 min · Individual

Melting Curve Graphing

Individuals track temperature of melting ice every 30 seconds for 10 minutes, plotting points on graphs. Compare class graphs to identify the plateau at 0°C. Extend by repeating with added salt.

Does everything melt and freeze at the same temperature?

Facilitation Tip

In Melting Curve Graphing, provide graph paper with pre-labeled axes to save time and reduce frustration, allowing focus on data interpretation.

What to look for

Pose the question: 'If you add salt to water, does it freeze at the same temperature? Why or why not?' Facilitate a class discussion where students can share initial ideas and then guide them towards understanding how impurities affect freezing points based on particle interactions.

Activity 04

• 20 min · Whole Class

Reversible Change Demo

Whole class observes a large ice block melting in a heated bowl, then refreezing poured water overnight. Vote on predictions beforehand and revisit results next lesson to confirm reversibility.

What happens to ice when it gets warm?

Facilitation Tip

During Reversible Change Demo, ask each pair to prepare a 30-second explanation of their observations before sharing with the class to build confidence.

What to look for

Provide students with two beakers, one containing ice cubes and the other containing liquid water at room temperature. Ask them to write one sentence describing what will happen to the ice cubes if left out and one sentence describing what will happen to the liquid water if placed in a freezer, referencing particle movement.

A few notes on teaching this unit

Start with a quick demonstration of ice melting in a beaker while students sketch particle arrangements at each stage. Use guided questions to connect energy input to particle behavior, avoiding jargon like 'latent heat' until later. Research shows that students need multiple opportunities to observe and explain before formalizing vocabulary, so keep explanations simple and repeatable across activities.

Students should explain melting and freezing using particle movement terms like energy gain or loss, vibration, and arrangement. They should also recognize that these changes are reversible and do not alter the substance itself, demonstrated through observations and measurements at each station.

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Watch Out for These Misconceptions

• During Station Rotation: Melting Challenges, watch for students assuming all substances melt at 0°C.

  Use thermometers to measure the melting points of ice, chocolate, and wax at each station. Have students compare their data in small groups and identify that different substances have unique melting points, reinforcing that water's 0°C is not universal.

• During Reversible Change Demo, watch for students describing melting as a chemical change that changes the substance.

  Ask students to taste the water before and after freezing to confirm it remains water. Use their observations to discuss how particle arrangement changes but the substance stays the same, linking back to the demo materials.

• During Freezing Point Investigation, watch for students expecting water to contract when freezing like most liquids.

  Have students measure the volume of water before and after freezing using a balloon or graduated cylinder. Discuss how the expansion is due to the open crystal lattice of ice, visible in the balloon experiment, and relate it to real-world examples like bursting pipes in winter.

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Methods used in this brief

• Stations Rotation