Science · Grade 5 · The Particle Nature of Matter · Term 1

Conservation of Matter in Changes

Students will explore the principle that matter is conserved during physical and chemical changes.

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

About This Topic

Conservation of matter means the total mass of substances stays the same during physical and chemical changes. Grade 5 students investigate this principle through experiments like dissolving salt in water or mixing baking soda and vinegar. They measure masses before and after changes, analyze data to confirm no matter is created or destroyed, and explain results using particle models.

This topic fits within the particle nature of matter unit and aligns with Ontario curriculum expectations for understanding matter interactions. Students practice key skills: collecting precise measurements, interpreting evidence, and constructing arguments. These build a foundation for chemical reactions and stoichiometry in later grades, while connecting to everyday observations like cooking or rusting.

Active learning shines here because abstract conservation counters common senses that substances vanish. When students handle balances for sealed reaction setups or track dissolving over time in pairs, they gather their own data, debate discrepancies, and solidify the concept through direct evidence.

Key Questions

1. Explain how the total mass of substances remains constant during a physical change.
2. Analyze experimental data to demonstrate the conservation of matter in a chemical reaction.
3. Construct an argument for why matter cannot be created or destroyed.

Learning Objectives

• Calculate the total mass of reactants before and after a physical change, such as dissolving, to demonstrate conservation of mass.
• Analyze experimental data from a sealed chemical reaction, like baking soda and vinegar, to verify that the total mass remains constant.
• Construct an argument, supported by evidence from investigations, explaining why matter cannot be created or destroyed during observable changes.
• Compare the mass of substances before and after a physical change and a chemical change, identifying similarities in mass conservation.
• Explain how the arrangement and movement of particles change during physical and chemical changes while the total number of particles remains constant.

Before You Start

Properties of Solids, Liquids, and Gases

Why: Students need to understand the basic characteristics of different states of matter to observe how they change during physical and chemical processes.

Introduction to Measurement and Mass

Why: Students must be able to accurately measure mass using a balance to collect data for conservation of matter experiments.

Key Vocabulary

Conservation of Matter	The principle stating that the total amount of matter in a closed system remains constant over time, meaning matter cannot be created or destroyed during physical or chemical changes.
Physical Change	A change in the form or appearance of a substance, but not its chemical composition. Examples include melting, freezing, dissolving, and changing shape.
Chemical Change	A change that results in the formation of new chemical substances with different properties. Examples include burning, rusting, and cooking.
Reactant	A substance that takes part in and undergoes change during a reaction. Reactants are on the left side of a chemical equation.
Product	A substance that is formed as a result of a chemical reaction. Products are on the right side of a chemical equation.

Watch Out for These Misconceptions

Common Misconception

Dissolved substances disappear, reducing total mass.

What to Teach Instead

Experiments show mass stays the same before and after dissolving, as particles spread out but remain. Active weighing stations let students test their ideas repeatedly, building confidence through consistent data.

Common Misconception

Mass is lost as gas escapes in chemical reactions.

What to Teach Instead

Sealed containers prove total mass constant, including gas. Hands-on bag reactions with immediate reweighing help students visualize all products, shifting focus from visible changes to total evidence.

Common Misconception

Physical changes create entirely new matter.

What to Teach Instead

Mass measurements reveal same particles in new forms, like liquid from solid. Student-led demos with melting ice encourage peer explanations, clarifying rearrangement over creation.

Active Learning Ideas

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.

35 min·Small Groups

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.

25 min·Pairs

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.

40 min·Individual

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.

45 min·Small Groups

Real-World Connections

• Bakers use the principle of conservation of matter when mixing ingredients for bread or cakes. While the ingredients undergo chemical changes during baking, the total mass of the dough or batter remains consistent, accounting for all atoms present.
• Chemists in industrial settings use mass balance calculations to ensure that no material is lost or gained during manufacturing processes. This is crucial for efficiency, safety, and environmental compliance in producing everything from plastics to pharmaceuticals.
• Environmental scientists monitor the mass of pollutants in water or air systems. Understanding that matter is conserved helps them track the movement and transformation of substances and predict their impact on ecosystems.

Assessment Ideas

Quick Check

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.'

Exit Ticket

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.

Discussion Prompt

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.'

Frequently Asked Questions

How to teach conservation of matter in grade 5 science?

Start with familiar changes like melting ice or dissolving sugar, using digital balances for accurate masses before and after. Guide students to predict outcomes, test in small groups, and analyze data trends. Link to particle theory by modeling with diagrams, reinforcing that atoms rearrange but total mass holds. This sequence builds from intuition to evidence-based understanding over several lessons.

What activities demonstrate conservation in chemical changes?

Use baking soda and vinegar in sealed bags or syringes to capture gas; students weigh reactants and products together. Alka-Seltzer in film canisters shows propulsion without mass loss. Emphasize closed systems to avoid escapes. Follow with class discussions on data, helping students argue for conservation using totals.

Common misconceptions about conservation of matter for grade 5?

Students often think dissolving means matter vanishes or gas means mass loss. They may believe state changes create new stuff. Address with repeated measurements in varied setups, like evaporation recovery or sealed reactions. Visual particle models paired with data charts help reframe these ideas effectively.

How can active learning help students understand conservation of matter?

Active approaches like hands-on weighing during dissolving or reactions make invisible processes visible through data students collect themselves. In pairs or groups, they predict, test, and revise ideas based on measurements, countering misconceptions from daily life. Collaborative analysis of class datasets reveals patterns, while real-time adjustments build procedural skills and excitement for science.