Science · Grade 5

Active learning ideas

Conservation of Matter in Changes

Active experiments help students see conservation of matter in action, making abstract particle ideas concrete. When students measure mass before and after changes, they build trust in evidence over assumptions, which is essential for grasping this principle.

• Ontario Curriculum Expectations
• 5-PS1-2
• 5-PS1-4

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

Activity 01

• Inquiry Circle
• 35 min · Small Groups

Precision Weighing: Dissolving Salt

Provide beakers with 100 mL water; students record mass, add 20 g salt, stir until dissolved, then reweigh. Have them evaporate water to recover salt and weigh again. Groups compare results and graph mass changes.

Explain how the total mass of substances remains constant during a physical change.

Facilitation Tip

At the Station Rotation, place a timer at each station so students stay on task and rotate smoothly.

What to look for

Provide students with a scenario: 'You mix 10g of salt with 100g of water in an open beaker and stir until dissolved.' Ask: 'What is the total mass of the solution? If you could somehow collect all the water vapor that evaporates, would the mass of the remaining salt be less than 10g? Explain your reasoning.'

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

Activity 02

• Inquiry Circle
• 25 min · Pairs

Sealed Bag Reaction: Baking Soda and Vinegar

In zip-top bags, students measure masses of baking soda and vinegar separately, seal together to react, then weigh the full bag. They feel the gas form and note total mass remains constant. Discuss particle rearrangement.

Analyze experimental data to demonstrate the conservation of matter in a chemical reaction.

What to look for

Give students two sealed bags. Bag A contains baking soda and vinegar. Bag B contains only water. Ask students to predict the mass of each bag after shaking Bag A (mixing reactants) and leaving Bag B (dissolving). Then, have them weigh each bag and record the mass. On the back, ask them to write one sentence explaining why the mass of Bag A did or did not change, and one sentence for Bag B.

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

Activity 03

• Inquiry Circle
• 40 min · Individual

Ice to Water Cycle

Students mass ice cubes in a container, let melt at room temp, reweigh water, then freeze and weigh ice. Extend by adding food coloring to track particles. Record observations in science notebooks.

Construct an argument for why matter cannot be created or destroyed.

What to look for

Pose the question: 'Imagine you burn a log in a fireplace. The ashes weigh much less than the log. Does this mean matter was destroyed? Use your knowledge of conservation of matter and particle models to explain what happened to the rest of the mass.'

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

Activity 04

• Stations Rotation
• 45 min · Small Groups

Stations Rotation: Change Types

Set up stations for melting chocolate, dissolving sugar, effervescent tablets in water, and candle in jar (mass before/after burn). Groups rotate, measure at each, compile class data on mass conservation.

Explain how the total mass of substances remains constant during a physical change.

What to look for

Provide students with a scenario: 'You mix 10g of salt with 100g of water in an open beaker and stir until dissolved.' Ask: 'What is the total mass of the solution? If you could somehow collect all the water vapor that evaporates, would the mass of the remaining salt be less than 10g? Explain your reasoning.'

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

A few notes on teaching this unit

Teachers should emphasize repeated measurements to build trust in the law of conservation, rather than relying on single demonstrations. Avoid rushing to explanations before students have collected their own data, and always link observations back to particle behavior. Research suggests hands-on weighing and sealed systems reduce misconceptions about mass loss.

Students will use balances to track mass before and after changes, explain why mass stays the same using particle language, and apply their observations to new scenarios. Success looks like confident predictions and clear reasoning tied to their data.

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Watch Out for These Misconceptions

• During Precision Weighing, watch for students who believe the dissolved salt disappears, reducing total mass.

  Ask students to check the balance again after dissolving and point to the salt particles still present in the water, reinforcing that mass stays constant even when particles spread out.

• During Sealed Bag Reaction, watch for students who think mass is lost as gas escapes.

  Have students feel the bag for pressure changes and reweigh it immediately to show the total mass includes the gas produced.

• During Ice to Water Cycle, watch for students who think melting creates new matter.

  Guide students to compare the mass of ice and water in identical containers, then ask them to draw particle models to explain the same particles in a different arrangement.

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Methods used in this brief

• Inquiry Circle
• Stations Rotation