Science · Grade 7

Active learning ideas

Evaporation and Distillation

Active learning works for evaporation and distillation because students often confuse the two processes or misunderstand how heat affects mixtures. Hands-on experiments let them see crystals form during evaporation and watch vapor turn back into liquid during distillation, making abstract particle theory concrete and memorable.

• Ontario Curriculum Expectations
• MS-PS1-2

• 30–50 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Experiential Learning
• 45 min · Small Groups

Lab Demo: Salt Recovery by Evaporation

Students dissolve salt in water, pour into shallow dishes, and place over low heat or in sunlight. They observe solvent loss over time, scrape recovered crystals, and measure mass before and after. Discuss why complete dryness matters for accurate recovery.

Explain how evaporation can be used to recover a dissolved solid from a solution.

Facilitation Tip

During the Salt Recovery by Evaporation demo, circulate with a handheld magnifier so students can observe salt crystal formation up close as the water gently evaporates.

What to look for

Present students with a diagram of a simple distillation apparatus. Ask them to label the key parts (e.g., heat source, flask, condenser, collection beaker) and briefly explain the role of each part in separating salt from water.

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

Activity 02

• Experiential Learning
• 50 min · Small Groups

Design Challenge: Simple Distillation Apparatus

Provide test tubes, rubber tubing, beakers, and hot plates. Groups sketch and build a setup to distill saltwater, heat to boil water, cool vapor in a collection tube, and taste test distillate. Record boiling temperatures and yield.

Differentiate between evaporation and distillation as separation techniques.

Facilitation Tip

Before the Simple Distillation Apparatus challenge, demonstrate how to seal tubing connections with playdough to prevent leaks, and have students practice with scrap pieces first.

What to look for

On an index card, have students write one sentence explaining the primary difference between evaporation and distillation. Then, ask them to list one situation where distillation would be a better choice than simple evaporation.

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

Activity 03

• Experiential Learning
• 40 min · Pairs

Pairs Comparison: Evaporation vs Distillation

Pairs prepare identical saltwater samples; one evaporates to recover salt, the other distills to recover water. They time processes, note products, and chart pros/cons on a shared poster. Conclude with class vote on best method for scenarios.

Design a simple distillation apparatus to separate salt from water.

Facilitation Tip

For the Pairs Comparison activity, provide a Venn diagram template with key terms like 'solvent recovery' and 'boiling points' to guide their discussion.

What to look for

Pose the question: 'Imagine you have a beaker of muddy water. Can you use evaporation or distillation to separate the mud from the water? Explain why or why not, and what separation technique might work better.' Facilitate a class discussion on the limitations of these methods for different types of mixtures.

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

Activity 04

• Experiential Learning
• 30 min · Whole Class

Whole Class: Boiling Point Investigation

Heat pure water, saltwater, and alcohol samples while class monitors thermometers. Identify boiling points, predict separation outcomes, and link to distillation choices. Graph data as a group.

Explain how evaporation can be used to recover a dissolved solid from a solution.

Facilitation Tip

During the Boiling Point Investigation, have students measure temperatures at two-minute intervals and graph results to reinforce the relationship between heat and phase changes.

What to look for

Present students with a diagram of a simple distillation apparatus. Ask them to label the key parts (e.g., heat source, flask, condenser, collection beaker) and briefly explain the role of each part in separating salt from water.

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

A few notes on teaching this unit

Teach evaporation and distillation by starting with real-world examples students recognize, like salt left in a pot after boiling pasta or distilled water in medical settings. Avoid rushing to complex lab equipment; instead, build from simple setups to formal apparatus. Research shows students grasp these concepts better when they design their own procedures rather than follow step-by-step instructions, so emphasize iteration and troubleshooting.

Successful learning looks like students confidently choosing the right separation method for a given mixture, explaining the role of boiling points, and troubleshooting their own distillation setups. They should articulate why evaporation leaves solutes behind while distillation recovers pure solvents.

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Watch Out for These Misconceptions

• During the Salt Recovery by Evaporation lab, watch for students who believe the salt also vaporizes and disappears with the water.

  Have students set up two evaporation dishes: one with salt water and one with plain water. As the water evaporates, guide them to observe the crystals left behind in the salt water dish and discuss why the solid remains due to its higher boiling point.

• During the Simple Distillation Apparatus challenge, watch for students who assume distillation works for any mixture, including suspensions like muddy water.

  Provide a beaker of muddy water as a test case. Ask students to predict and observe what happens when they attempt distillation, then facilitate a discussion on why filtration or sedimentation would be better methods for such mixtures.

• During the Simple Distillation Apparatus challenge, watch for students who think distillation requires expensive or specialized equipment.

  Challenge students to build a functional apparatus using only a flask, tubing, a beaker, and ice water. Circulate to troubleshoot leaks or poor condensation, and have groups share their most effective designs with the class.

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Methods used in this brief

• Experiential Learning