Science · Grade 3 · Matter and Its Properties · Term 2

Melting and Freezing

Students will observe and describe the processes of melting and freezing, understanding them as reversible physical changes.

• Ontario Curriculum Expectations
• 2-PS1-4

About This Topic

Melting and freezing are reversible physical changes that occur when matter absorbs or releases thermal energy. Grade 3 students observe solids, such as ice cubes, turning into liquids as temperature rises above their melting point. They also watch liquids, like water, solidify into crystals when cooled below the freezing point. These processes connect to daily experiences, from popsicles melting on warm days to frost forming overnight.

In the Matter and Its Properties unit, this topic builds understanding of states of matter and energy transfer. Students compare how different substances, including butter or salt water, melt or freeze at varying temperatures. They explain causes through simple models and predict outcomes, fostering scientific inquiry skills essential for Ontario curriculum expectations.

Active learning benefits this topic greatly. Experiments with safe, familiar materials let students test variables directly, witness reversibility in real time, and collaborate on predictions. Group discussions after trials help clarify energy roles and dispel confusion, making abstract ideas concrete and memorable.

Key Questions

1. Explain what causes a solid to melt and a liquid to freeze.
2. Compare the energy changes involved in melting versus freezing.
3. Predict how different substances might melt or freeze at varying temperatures.

Learning Objectives

• Explain the cause of melting and freezing in terms of thermal energy transfer.
• Compare the energy changes required for melting versus freezing for a given substance.
• Predict how changes in temperature affect the state of water.
• Describe melting and freezing as reversible physical changes.

Before You Start

Solids, Liquids, and Gases

Why: Students need to identify and describe the basic properties of solids and liquids to observe their changes.

Introduction to Heat and Temperature

Why: Understanding that heat can change temperature is fundamental to grasping why melting and freezing occur.

Key Vocabulary

Melting	The process where a solid changes into a liquid due to an increase in temperature and absorption of thermal energy.
Freezing	The process where a liquid changes into a solid due to a decrease in temperature and release of thermal energy.
Thermal Energy	Energy related to heat; its transfer causes changes in the temperature and state of matter.
Reversible Change	A physical change that can be undone, returning the substance to its original state.

Watch Out for These Misconceptions

Common Misconception

Melting and freezing are chemical changes that create new substances.

What to Teach Instead

These are physical changes; the substance stays the same, just changes state. Hands-on reversibility demos, like refreezing melted ice, let students see and test this directly. Group sharing of before-and-after observations reinforces the distinction.

Common Misconception

All solids melt and all liquids freeze at the same temperature.

What to Teach Instead

Each substance has unique melting and freezing points. Experiments comparing ice, butter, and salt water reveal differences. Student predictions followed by measurements build accurate mental models through trial and data comparison.

Common Misconception

Freezing always makes things shrink.

What to Teach Instead

Water expands when freezing into ice. Volume measurements before and after freezing show this anomaly. Active volume checks with marked containers help students notice and discuss exceptions to general rules.

Active Learning Ideas

Observation Lab: Ice Melting Conditions

Provide ice cubes in four setups: room temperature bowl, warm water, shaded spot, and sunny spot. Students time melting rates, measure water volume changes, and record temperature every 5 minutes. Discuss which condition melts fastest and why.

30 min·Small Groups

Demo: Salt on Ice

Place ice cubes on plates; sprinkle salt on half. Students observe faster melting on salted ice, touch to feel temperature drop, and hypothesize about salt's effect on freezing point. Repeat with water freezing tests.

25 min·Whole Class

Pairs Experiment: Freezing Salt Water

Pairs mix varying salt amounts in water cups, place in freezer overnight, then check and measure ice thickness next day. Predict and compare results, noting less ice forms in saltier solutions.

45 min·Pairs

Prediction Challenge: Substance Melts

Show butter, chocolate, and crayons at room temperature. Students predict melting order, heat gently, and time each. Chart results and revise predictions based on observations.

35 min·Small Groups

Real-World Connections

• Ice cream makers use the principle of freezing to turn liquid ingredients into a solid dessert. They often add salt to the ice surrounding the inner container to lower the freezing point of the ice, making it colder and freezing the ice cream faster.
• Chefs and bakers utilize melting and freezing daily. Butter melts to incorporate into batters, and water freezes to form ice for drinks or to create frozen desserts like sorbet.
• Winter road maintenance crews manage melting and freezing cycles. They spread salt on roads to lower the freezing point of water, preventing ice formation or melting existing ice to improve road safety.

Assessment Ideas

Exit Ticket

Provide students with a small cup of ice cubes and a warm lamp. Ask them to observe and record two changes they see. Then, ask them to write one sentence explaining what caused the ice to change and one sentence describing how they could reverse the change.

Discussion Prompt

Pose the question: 'Imagine you have a glass of water and a block of ice. What needs to happen to the ice for it to become water, and what needs to happen to the water for it to become ice? What is the same about these two processes, and what is different?' Facilitate a class discussion focusing on energy transfer and reversibility.

Quick Check

Show students pictures of different scenarios: a puddle drying up, frost on a window, a popsicle melting, water turning to ice in a freezer. Ask students to label each picture with either 'Melting' or 'Freezing' and briefly explain their choice.

Frequently Asked Questions

What causes a solid to melt in grade 3 science?

Solids melt when they absorb enough thermal energy to overcome forces holding particles together, raising temperature above the melting point. Students explore this by heating ice or butter and measuring temperature changes. Everyday examples like snow melting in spring connect concepts to real life, while predictions strengthen reasoning skills.

How does active learning help teach melting and freezing?

Active learning engages students through hands-on trials with ice, salt, and household items, allowing direct observation of reversible changes. They manipulate variables like temperature or additives, predict outcomes, and discuss in groups. This approach clarifies energy transfer, corrects misconceptions via evidence, and boosts retention compared to lectures alone.

Common misconceptions about melting and freezing for grade 3?

Students often think melting creates new matter or all substances change state at zero degrees Celsius. They may believe freezing shrinks everything. Targeted demos and prediction activities expose these ideas, with peer discussions and repeated observations helping build correct understandings aligned to curriculum standards.

Activities for melting and freezing Ontario grade 3 science?

Try ice melting races under different conditions, salt-lowering freezing point demos, and substance prediction challenges with butter or chocolate. These 25-45 minute activities use simple materials, suit small groups or whole class, and include prediction, observation, and discussion steps to meet inquiry expectations effectively.