Scientific Inquiry and the Natural World · 5th Class

Active learning ideas

Phase Changes: Melting and Freezing

Active learning helps students grasp phase changes because the invisible processes of energy transfer become visible through hands-on observation. Timing melting ice or watching wax solidify turns abstract concepts into concrete, memorable experiences that build lasting understanding.

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

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

Activity 01

• Experiential Learning
• 30 min · Pairs

Melting Race: Ice Cubes Under Conditions

Provide pairs with identical ice cubes on plates. Place one in sunlight, one shaded, one salted, and one with black paper underneath. Students measure melting time and temperature every 2 minutes, then graph results to compare conditions.

Explain the energy changes that occur during melting and freezing.

Facilitation Tip

During the Melting Race, have students record start times and weights to standardize conditions, then compare melting rates in groups to identify variables like surface area or insulation.

What to look for

Provide students with three scenarios: 1. A glass of ice water at 0°C. 2. A puddle on a road at -5°C. 3. A chocolate bar left in the sun at 25°C. Ask students to write the state of water or chocolate in each scenario and briefly explain why.

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

Activity 02

• Experiential Learning
• 45 min · Small Groups

Freezing Point Investigation: Salt Solutions

Mix varying salt concentrations in water samples. Students place them in a freezer and check freezing times hourly, recording temperatures. Discuss how salt affects the freezing point using class data.

Analyze how impurities can affect the melting and freezing points of substances.

Facilitation Tip

For the Freezing Point Investigation, ensure students use identical containers and stir salt solutions gently but consistently to maintain fair temperature readings.

What to look for

Show students a thermometer reading. Ask them to hold up a card indicating 'Melting', 'Freezing', or 'Neither' if the temperature is 0°C. Then, ask them to explain their choice, focusing on the energy changes involved.

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

Activity 03

• Experiential Learning
• 35 min · Pairs

Temperature Logging: Paraffin Wax Cycle

Heat paraffin wax to melt, log temperature every minute until liquid, then cool and log freezing. Pairs plot graphs to identify plateaus where phase change occurs without temperature rise.

Predict the state of water at different temperatures.

Facilitation Tip

During the Temperature Logging activity, assign small groups to track wax temperatures every 30 seconds so the class can collaboratively graph the entire freezing cycle.

What to look for

Pose the question: 'Why do we put salt on icy roads instead of just letting the ice melt?' Facilitate a discussion where students explain the concept of freezing point depression and its practical application.

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

Activity 04

• Experiential Learning
• 25 min · Small Groups

Prediction Stations: Water States

Set up stations with thermometers showing -10°C, 0°C, 10°C, 100°C. Students predict water's state, test with small samples if possible, and justify using particle models.

Explain the energy changes that occur during melting and freezing.

What to look for

Provide students with three scenarios: 1. A glass of ice water at 0°C. 2. A puddle on a road at -5°C. 3. A chocolate bar left in the sun at 25°C. Ask students to write the state of water or chocolate in each scenario and briefly explain why.

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

A few notes on teaching this unit

Teach this topic by anchoring lessons in everyday examples students can relate to, like ice melting or chocolate softening. Avoid introducing the term latent heat too early; instead, let students articulate energy changes through observations before formalizing the concept. Research shows that guided inquiry with structured observations reduces misconceptions about instantaneous phase changes.

Successful learning looks like students accurately predicting phase changes, measuring temperature plateaus during transitions, and explaining how impurities or energy affect melting and freezing points. They should use evidence from activities to challenge initial misconceptions and articulate energy’s role in state changes.

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Watch Out for These Misconceptions

• During the Melting Race, watch for students assuming ice melts at the exact moment it reaches 0°C.

  Use the Melting Race to demonstrate that melting takes time and temperature remains constant during the phase change; have students graph time versus temperature to see the plateau.

• During the Freezing Point Investigation, watch for students believing impurities do not affect freezing points.

  In the Freezing Point Investigation, guide students to compare salted and pure water freezing times, then discuss how salt disrupts ice crystal formation to lower the freezing point.

• During the Temperature Logging activity, watch for students thinking no energy changes occur during melting or freezing.

  In the Temperature Logging activity, have students note the steady temperature during wax’s phase change and connect it to energy being used to break or form bonds, not raise temperature.

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Methods used in this brief

• Experiential Learning