Science · Grade 3

Active learning ideas

Dissolving and Mixtures

Active experiments let students see dissolving and mixtures in real time, building lasting understanding. Hands-on testing of salt, sugar, and sand helps correct misconceptions faster than passive discussion alone. Observing changes in their own cups keeps engagement high and ideas concrete.

• Ontario Curriculum Expectations
• 2-PS1-2

• 20–50 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Experiential Learning
• 30 min · Pairs

Dissolving Race: Temperature Test

Pairs predict and test how quickly salt dissolves in hot, room-temperature, and cold water. Measure water temperatures with thermometers, stir consistently for 1 minute intervals, and time until clear. Record results in a class chart to compare patterns.

Differentiate between a substance that dissolves and one that does not.

Facilitation Tip

During Dissolving Race: Temperature Test, circulate to remind teams to stir each cup the exact same number of times every 30 seconds.

What to look for

Provide students with three small containers: one with salt water (solution), one with sand in water (mixture), and one with plain water. Ask students to label each container and write one sentence explaining why the salt disappeared but the sand did not.

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

Activity 02

• Experiential Learning
• 45 min · Small Groups

Mixture Separation Stations

Set up stations for filtering sand-water mixtures with coffee filters, evaporating salt water in shallow dishes under heat lamps, and settling dirt in jars. Small groups rotate every 10 minutes, sketch methods, and note what works best.

Explain how temperature can affect the rate at which a substance dissolves.

Facilitation Tip

For Mixture Separation Stations, provide labeled tweezers and filter paper in advance to avoid delays when students begin separating.

What to look for

Present students with a scenario: 'Imagine you have a glass of cold water and a glass of hot water. You add one spoonful of sugar to each. Which glass will have dissolved sugar faster? Explain your thinking using the word 'temperature'.

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

Activity 03

• Experiential Learning
• 50 min · Small Groups

Design Challenge: Clean Water

Provide mixtures of sand, salt, and water. Groups design and build a separation device using sieves, filters, and evaporation setups. Test prototypes, refine based on results, and present to the class.

Design a method to separate a dissolved solid from a liquid.

Facilitation Tip

In Design Challenge: Clean Water, limit initial materials to five items to push creativity within constraints.

What to look for

Ask students to think about how they might separate the salt from the water in a saltwater solution. Guide the discussion towards methods like boiling the water to let it evaporate, leaving the salt behind. Prompt them to consider if this would work for sand in water.

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

Activity 04

• Experiential Learning
• 20 min · Individual

Observation Jars: Mix and Settle

Individuals fill jars with water and add sugar, sand, or chalk powder. Observe over 10 minutes with periodic notes on changes. Shake to stir and compare settling rates.

Differentiate between a substance that dissolves and one that does not.

Facilitation Tip

Use Observation Jars: Mix and Settle to model precise note-taking by recording times and changes directly on the jar labels.

What to look for

Provide students with three small containers: one with salt water (solution), one with sand in water (mixture), and one with plain water. Ask students to label each container and write one sentence explaining why the salt disappeared but the sand did not.

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

A few notes on teaching this unit

Teachers should let students predict outcomes before testing, then revisit predictions after results. Avoid telling students the 'right' answer too soon; instead, ask guiding questions like, 'What do you notice about the sugar in the warm cup?' Research shows this approach builds stronger conceptual understanding. Always connect back to the vocabulary of solutions and mixtures after each activity to reinforce terms in context.

Students will accurately describe dissolving versus mixtures, explain temperature’s role, and choose appropriate separation methods. Clear observations, precise vocabulary, and thoughtful predictions show mastery. Group sharing ensures all students connect their findings to key concepts.

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Watch Out for These Misconceptions

• During Dissolving Race: Temperature Test, watch for students who assume stirring is the only cause of dissolving.

  Have students compare identical amounts of sugar in warm and cold water with no stirring, then add stirring to the cold cup only. The warm cup should dissolve faster, proving temperature matters more.

• During Observation Jars: Mix and Settle, watch for students who believe sand disappears when mixed.

  Point to the bottom layer of sand and ask, 'Is the sand still here? How can you tell?' Guide them to label the jar to track visible solids.

• During Mixture Separation Stations, watch for students who think evaporation removes both dissolved and undissolved solids.

  Ask them to compare the results of evaporating salt water and sand water side by side. The salt crystals will reappear, while sand will remain a residue.

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Methods used in this brief

• Experiential Learning