Changes of State: Melting and Freezing

Active learning helps Year 5 students grasp changes of state by moving beyond abstract explanations to direct observation and experimentation. Hands-on activities make particle movement visible through measurable outcomes like freezing time and melting patterns, turning theory into evidence they can see and touch.

• Year 5
• Science
• 4 activities
• 25 min–45 min

Learning Objectives

1. Explain the particle behavior during the melting of a solid into a liquid, referencing temperature changes.
2. Compare the energy input required for melting with the energy released during freezing for a given substance.
3. Predict the effect of adding a common impurity, like salt, on the melting point of ice.
4. Classify observed changes of state as melting or freezing based on temperature and particle movement.

Experiential Learning

⏱ 45 min·Pairs

Experiment: Salt vs Pure Water Freezing

Provide pairs with pure water and saltwater in identical containers; place in freezer and check hourly. Students record freezing times and temperatures, then graph results. Discuss why salt delays freezing.

Prepare & details

Explain how adding heat changes the behavior of particles during melting.

Facilitation Tip: During Experiment: Salt vs Pure Water Freezing, circulate to ensure students measure the same volume of water and salt for fair comparison.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

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

Stations Rotation

⏱ 40 min·Small Groups

Stations Rotation: Melting Conditions

Set up stations with ice cubes on foil under different conditions: room temp, warm water bath, insulated wrap, and with salt. Groups rotate every 10 minutes, timing melts and noting particle clues like puddles forming.

Prepare & details

Compare the energy changes involved in melting versus freezing.

Facilitation Tip: During Station Rotation: Melting Conditions, place a timer at each station so students can focus on recording melting times without losing track of their observations.

Setup: Tables/desks arranged in 4-6 distinct stations around room

Materials: Station instruction cards, Different materials per station, Rotation timer

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

Experiential Learning

⏱ 30 min·Whole Class

Whole Class: Temperature Graphing

Melt ice in a shared beaker while class logs temperature every minute on a shared chart. Predict plateaus during phase change; review graph to explain constant temperature despite added heat.

Prepare & details

Predict how impurities might affect the melting point of a substance.

Facilitation Tip: During Whole Class: Temperature Graphing, model how to label axes and plot points accurately before students begin working independently.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

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

Experiential Learning

⏱ 25 min·Individual

Individual: Predict and Test Chocolate

Students predict melting times for chocolate pieces at varied spots: hand, desk, fridge. Test, time, and journal particle explanations with sketches.

Prepare & details

Explain how adding heat changes the behavior of particles during melting.

Facilitation Tip: During Individual: Predict and Test Chocolate, ask students to record both their prediction and the actual melting time to emphasize the importance of evidence-based reasoning.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

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

Teaching This Topic

Teachers should anchor instruction in everyday materials students recognize, like ice and chocolate, to make particle theory concrete. Emphasize reversibility by having students refreeze melted materials, which combats the misconception that changes of state create new substances. Avoid rushing to explanations; let students wrestle with observations first, then guide them to connect evidence to particle movement.

What to Expect

Successful learning looks like students using precise vocabulary to describe melting and freezing, explaining particle behavior in real-world examples, and applying their understanding to predict outcomes in new contexts. They should connect temperature changes to observable changes in state and justify predictions with evidence from experiments.

Watch Out for These Misconceptions

Common Misconception

During Experiment: Salt vs Pure Water Freezing, watch for students who believe the salt changes the water into a new substance.

What to Teach Instead

Use the experiment’s reversibility test—refreezing the melted salt water—to show that it returns to ice, proving the substance remains water with salt dissolved in it. Have students compare the mass of the water before and after freezing to reinforce that mass is conserved.

Common Misconception

During Station Rotation: Melting Conditions, watch for students who assume all substances melt at the same temperature.

What to Teach Instead

Have students compare melting times across stations using the same heat source, then ask them to rank substances by melting point. Use a class chart to compile data, highlighting differences in melting times as evidence of varying melting points.

Common Misconception

During Whole Class: Temperature Graphing, watch for students who think particles stop moving completely when frozen.

What to Teach Instead

Use the graphing activity to connect cooling curves to particle movement: as the line flattens, point out that particles are vibrating in place, not stopping. Have students act out particle movement during the graphing discussion to visualize this concept.

Assessment Ideas

Exit Ticket

After Experiment: Salt vs Pure Water Freezing, ask students to write two sentences: one describing what happened to the particles as the salt water froze, and another explaining how this shows that melting and freezing are reversible.

Quick Check

During Station Rotation: Melting Conditions, listen for students using terms like 'melting point' or 'heat source' to explain their observations. Note if they accurately link the melting time to the substance’s properties.

Discussion Prompt

After Whole Class: Temperature Graphing, ask students to share their graphs and explain how the flat parts of the line relate to particle movement. Use their responses to assess whether they connect temperature plateaus to changes in state.

Extensions & Scaffolding

• Challenge students to design an experiment testing how sugar affects freezing time in water, extending the salt investigation.
• Provide sentence stems with word banks for students who struggle to articulate particle explanations during discussions.
• Ask deeper questions, such as: 'Could a substance exist between solid and liquid? Explore slime or lava to investigate states of matter further.'

Key Vocabulary

Melting	The process where a solid changes into a liquid due to an increase in temperature and particle movement.
Freezing	The process where a liquid changes into a solid due to a decrease in temperature and particle movement.
Particle Vibration	The movement of tiny particles within a substance; increased vibration leads to melting, decreased vibration leads to freezing.
Melting Point	The specific temperature at which a solid substance begins to melt and change into a liquid.
Impurity	A substance that is present in another substance but is not a part of its pure composition, potentially affecting its properties like melting point.