Scientific Inquiry and the Natural World · 6th Class

Active learning ideas

Changes of State: Melting & Freezing

Active learning works particularly well for changes of state because students need to see, touch, and feel the science in action. When students physically observe melting ice or freezing water, the abstract concept becomes concrete, and misconceptions are easier to address. Hands-on activities also encourage careful observation, which is critical when distinguishing between physical and chemical changes.

• NCCA Curriculum Specifications
• NCCA: Primary - Materials
• NCCA: Primary - Properties and Characteristics of Materials

• 20–40 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Think-Pair-Share
• 20 min · Pairs

Think-Pair-Share: The Kitchen Chemist

The teacher lists five changes: frying an egg, melting ice, burning toast, dissolving sugar, and rusting a nail. Students work in pairs to decide which are reversible and which are not, providing one piece of evidence for each choice.

Explain why a substance's temperature remains constant during a phase change.

Facilitation Tip

During The Kitchen Chemist, remind students to focus on observable clues like texture or temperature rather than just the disappearance of a substance.

What to look for

Provide students with a graph showing temperature over time for a substance being heated and then cooled. Ask them to: 1. Identify the plateau where melting occurs. 2. Explain in one sentence why the temperature does not change during this plateau.

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

Activity 02

• Inquiry Circle
• 40 min · Small Groups

Inquiry Circle: The Mystery Reaction

Groups are given vinegar and baking soda. They must observe the reaction, identify the signs of a chemical change (bubbles/gas), and then try to figure out if they can get the original materials back, leading to a discussion on irreversibility.

Analyze the role of heat energy in melting and freezing.

Facilitation Tip

In The Mystery Reaction, circulate with a small cup of vinegar and baking soda to prompt quiet groups who may be stuck on how to test their predictions.

What to look for

Show students two identical containers, one with ice cubes and one with water at room temperature. Ask: 'If we add the same amount of heat energy to both, which will reach its melting/freezing point first, and why?'

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

Activity 03

• Gallery Walk
• 30 min · Whole Class

Gallery Walk: Change in Action

Students set up 'before and after' stations for different changes (e.g., a crushed can, a burnt piece of paper, a dissolved salt solution). Classmates walk around and use a checklist to identify if the change was physical or chemical.

Design an experiment to compare the melting points of different solids.

Facilitation Tip

For the Gallery Walk, assign a 'recorder' in each group to ensure all observations are captured before rotating to the next station.

What to look for

Pose the question: 'Imagine you have a block of ice and a block of butter, both at 0°C. Which will melt faster if you place them in a warm room? Use the terms 'melting point' and 'heat energy' in your explanation.'

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

A few notes on teaching this unit

Teachers should emphasize observation first, labeling second, before introducing the terms 'physical' or 'chemical.' Avoid starting with definitions; instead, let students experience the change and describe it in their own words. Research shows that students retain concepts better when they connect new knowledge to familiar examples, so begin with everyday changes like ice melting or butter softening before moving to lab-based examples.

Successful learning looks like students confidently using terms such as 'melting point,' 'freezing point,' and 'physical change' while explaining their observations. They should recognize that dissolving salt in water is a physical change by retrieving the salt through evaporation. Students should also identify the 'clues' of a chemical reaction in everyday contexts, like the kitchen or garden.

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Watch Out for These Misconceptions

• During The Kitchen Chemist, watch for students who assume dissolving salt in water is a chemical change because the salt 'disappears.'

  During The Kitchen Chemist, redirect students by having them set aside a sample of the saltwater and observe as the water evaporates over a few days, recovering the salt crystals to demonstrate it is still the same substance.

• During The Gallery Walk, listen for students who claim all reversible changes are physical and all irreversible changes are chemical.

  During The Gallery Walk, challenge students to find an exception by showing them a simple chemical reaction, like baking soda and vinegar, which produces a gas and is irreversible but not a change of state. Use this to reinforce the 'new material' rule.

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Methods used in this brief

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