Separating Mixtures: Evaporation

Active learning helps Year 5 students grasp evaporation’s role in separating mixtures by letting them observe real changes over time. Hands-on experiments make abstract ideas—like water becoming vapor and solids remaining—tangible and memorable, especially when students see their own results instead of just reading about them.

• Year 5
• Science
• 4 activities
• 30 min–50 min

Learning Objectives

1. Explain the process of evaporation as a method to separate a dissolved solid from a liquid.
2. Design an experiment to investigate the rate of evaporation under varying conditions, such as temperature or surface area.
3. Analyze the limitations of using evaporation to separate mixtures, identifying scenarios where it is not effective.
4. Predict the outcome of evaporating a saltwater solution and identify the solid residue.
5. Compare the effectiveness of evaporation versus filtration for separating different types of mixtures.

Inquiry Circle

⏱ 45 min·Small Groups

Fair Test: Evaporation Rates

Provide saltwater in shallow dishes. Students place dishes in sun, shade, and by a fan, measuring water level daily with rulers. They record data in tables and graph results to compare rates.

Prepare & details

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

Facilitation Tip: During Fair Test: Evaporation Rates, remind students to measure volumes precisely with graduated cylinders to ensure their comparisons are valid.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Stations Rotation

⏱ 50 min·Small Groups

Stations Rotation: Salt Recovery

Set up stations with saltwater solutions of varying concentrations. Groups heat gently on hot plates or use sunlight to evaporate, then weigh recovered salt. Rotate stations, noting differences in yield.

Prepare & details

Analyze the limitations of using evaporation for all types of mixtures.

Facilitation Tip: In Station Rotation: Salt Recovery, circulate with a checklist to note which groups correctly identify that only dissolved solids remain after evaporation.

Setup: Tables/desks arranged in 4-6 distinct stations around room

Materials: Station instruction cards, Different materials per station, Rotation timer

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

Inquiry Circle

⏱ 40 min·Pairs

Design Challenge: Quick Evaporation

Pairs design setups to evaporate saltwater fastest, using trays, cloths, or heat sources safely. Test predictions, measure time to dryness, and present best method to class.

Prepare & details

Design an experiment to recover salt from a saltwater solution.

Facilitation Tip: For Design Challenge: Quick Evaporation, provide timers and thermometers so students collect measurable data to support their claims.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Inquiry Circle

⏱ 30 min·Individual

Observation Journal: Classroom Drying

Students spill saltwater drops on paper or saucers around the room. Over a week, they journal daily changes, sketching crystals and linking to evaporation theory.

Prepare & details

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

Facilitation Tip: In Observation Journal: Classroom Drying, model how to record daily changes with both sketches and written observations to build consistency across groups.

Setup: Groups at tables with access to source materials

Materials: Source material collection, Inquiry cycle worksheet, Question generation protocol, Findings presentation template

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

Teaching This Topic

Teach evaporation by starting with what students already know about water disappearing, then connecting it to separating mixtures. Avoid rushing to conclusions; let students test their own hypotheses first. Research suggests that students learn best when they see both successful and failed attempts, so plan for controlled comparisons and guided reflection. Focus on the reversibility of the process to reinforce conservation of mass, a concept students often find challenging.

What to Expect

Students will confidently link evaporation to dissolving solids, predict outcomes for different mixtures, and explain why some mixtures cannot be separated this way. They will also plan fair tests, collect data, and justify their methods using scientific reasoning rather than guesswork.

Watch Out for These Misconceptions

Common Misconception

During Station Rotation: Salt Recovery, watch for students who assume evaporation works for all mixtures, including sand and water.

What to Teach Instead

Have students test a sand-water mixture at one station and observe that sand remains mixed rather than forming crystals. During the group discussion, ask them to classify the mixture as soluble or insoluble before deciding on a separation method.

Common Misconception

During Observation Journal: Classroom Drying, watch for students who believe the salt disappears or changes into something else.

What to Teach Instead

Ask students to weigh the dish before and after evaporation, then compare results in a class table. Use the data to discuss how mass is conserved and the salt remains chemically unchanged, just in crystal form.

Common Misconception

During Fair Test: Evaporation Rates, watch for students who think faster heating always produces more salt crystals.

What to Teach Instead

Have groups compare gentle heat with direct strong heat and measure the amount of salt recovered. In the plenary, graph the results together to show that splattering reduces yield, linking energy input to practical outcomes.

Assessment Ideas

Exit Ticket

After Observation Journal: Classroom Drying, give students a small beaker of saltwater and ask them to draw and label what they expect to see after the water evaporates. They should write one sentence explaining why the solid remains, referencing their observations from the activity.

Quick Check

During Station Rotation: Salt Recovery, present students with sand-water, salt-water, and oil-water mixtures. Ask them to identify which can be separated by evaporation and explain why the others require different methods, using their station observations as evidence.

Discussion Prompt

After Design Challenge: Quick Evaporation, pose the question: 'Would evaporation be the best method to recover pure water from saltwater? Why or why not?' Use students’ arguments about advantages, such as simplicity, and disadvantages, like time and energy use, to assess their understanding of method selection.

Extensions & Scaffolding

• Challenge early finishers to design a method to recover both salt and water from a saltwater solution, considering energy use and time.
• Scaffolding for struggling learners: Provide pre-labeled diagrams of evaporation setups with missing labels they must complete using key terms.
• Deeper exploration: Ask students to research and present on real-world uses of evaporation, such as salt harvesting or water purification, and compare methods.

Key Vocabulary

Evaporation	The process where a liquid turns into a gas or vapor. In this context, it's how water disappears from a solution, leaving the dissolved solid behind.
Dissolved Solid	A solid substance that has broken down and dispersed evenly within a liquid, forming a solution. Examples include salt or sugar in water.
Solute	The substance that is dissolved in a solvent to form a solution. In a saltwater solution, salt is the solute.
Solvent	The substance that dissolves a solute to form a solution. Water is a common solvent, like in saltwater.
Residue	The solid material left behind after a liquid has evaporated or been removed.