Separating Solutions and Colloids

Active investigations let students see how separation methods work with their own eyes, turning abstract ideas about particle size and solubility into memorable evidence. Hands-on trials with real mixtures build confidence that techniques like evaporation and chromatography actually recover original substances instead of changing them.

• Year 5
• Science
• 4 activities
• 20 min–40 min

Learning Objectives

1. Explain the process of evaporation as a method to recover a dissolved solid from a liquid.
2. Compare the separation principles of distillation and chromatography for different types of mixtures.
3. Evaluate the suitability of evaporation, distillation, or chromatography for separating specific given solutions and colloids.
4. Identify the components of a mixture after separation using evaporation, distillation, or chromatography.

Inquiry Circle

⏱ 25 min·Pairs

Pairs: Marker Chromatography

Pairs draw marker lines on filter paper strips, suspend in shallow water, and observe pigment separation over 10 minutes. They measure travel distances and discuss why colors separate differently. Record results in notebooks for class comparison.

Prepare & details

Explain the process of evaporation to recover salt from saltwater.

Facilitation Tip: During Marker Chromatography, remind pairs to handle papers by the edges to avoid smudging and to make a straight baseline above the solvent to ensure clean separation.

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

⏱ 40 min·Small Groups

Small Groups: Salt Evaporation Race

Groups place equal saltwater volumes in shallow dishes under lamps or sunlight, weigh daily, and note when salt crystals form. Compare evaporation rates and purity of recovered salt. Discuss variables like surface area.

Prepare & details

Compare the principles behind distillation and chromatography.

Facilitation Tip: In the Salt Evaporation Race, circulate with a timer so groups see how heat speed affects crystal appearance and connect time to energy input.

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·Whole Class

Whole Class: Tea Bag Distillation

Teacher demonstrates heating tea-stained water through a straw condenser into a cold cup; students predict outcomes and draw particle models before and after. Class discusses boiling point differences in water and solutes.

Prepare & details

Assess the most appropriate separation technique for different types of solutions.

Facilitation Tip: For Tea Bag Distillation, place the cold surface close enough to the rising steam so condensation happens quickly and students observe the purified water collect.

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

⏱ 20 min·Individual

Individual: Colloid Filter Test

Students filter milk, muddy water, and saltwater through coffee filters, observe residues, and classify mixtures. Note which pass through completely and explain using size of particles.

Prepare & details

Explain the process of evaporation to recover salt from saltwater.

Facilitation Tip: When running the Colloid Filter Test, give each student a dropper to control the flow through filter paper and watch for the moment when clear filtrate appears.

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

Teachers should start with quick demos that show surprising results, like ink splitting into colors or salt reappearing after heating. Avoid long explanations before hands-on work; let students notice patterns and ask questions first. Research shows guided inquiry with real materials builds stronger conceptual change than lectures alone.

What to Expect

Students will correctly match separation techniques to mixtures, explain why filters fail on solutions, and describe how heat or solvent flow moves particles. They will use new vocabulary in discussions and diagrams to show understanding of reversible changes.

Watch Out for These Misconceptions

Common Misconception

During Marker Chromatography, watch for students who think all colors separate by size alone.

What to Teach Instead

Pause the activity after the first run and ask groups to compare ink colors that traveled far with those that stayed near the baseline, prompting them to notice solubility differences and adhesion to paper.

Common Misconception

During Salt Evaporation Race, watch for students who believe the salt disappears when the water boils away.

What to Teach Instead

Have students touch the dry dish with a clean spoon after cooling and taste a pinch to confirm the salt remains, then revisit the idea of solvent removal versus solute loss.

Common Misconception

During Colloid Filter Test, watch for students who think filters can remove dissolved particles like salt.

What to Teach Instead

Ask students to compare the clear filtrate from muddy water with the cloudy filtrate from milk, then discuss why filters catch large colloid particles but let dissolved salts pass through.

Assessment Ideas

Quick Check

After Marker Chromatography, present students with three beakers labeled saltwater, ink, and milk, and ask them to write which separation technique—evaporation, distillation, or chromatography—would work best for each mixture and explain their choice.

Exit Ticket

During Salt Evaporation Race, give students a card to draw a simple diagram showing how evaporation separates salt from water, including labels for salt, water, heat source, and recovered salt.

Discussion Prompt

After Tea Bag Distillation, facilitate a class discussion using the prompt: 'You have a mixture of two different colored marker inks. Which separation technique would you choose and why? What do you expect to see on the paper?'

Extensions & Scaffolding

• Challenge: Ask students to design a two-step separation for a mixture of salt, sand, and food coloring, predicting what will happen at each stage.
• Scaffolding: Provide pre-marked strips for chromatography and safety scissors for cutting filter paper to reduce setup errors.
• Deeper exploration: Have students research how distillation is used in real-world settings like desalination plants or perfume production, then present one example to the class.

Key Vocabulary

Solution	A homogeneous mixture where one substance dissolves completely into another, forming a clear liquid with no visible particles.
Colloid	A mixture where particles are dispersed throughout but are not fully dissolved, scattering light and not settling quickly.
Evaporation	The process where a liquid turns into a gas or vapor, typically due to heating, leaving behind any dissolved solids.
Distillation	A method used to separate liquids with different boiling points by heating the mixture and collecting the vapor that condenses back into a liquid.
Chromatography	A technique used to separate mixtures, especially colored compounds, by passing them through a medium where different components move at different rates.