Science · Year 7

Active learning ideas

Advanced Separation: Distillation and Chromatography

Active learning works well here because students can physically see and measure the separation of mixtures. When they handle real apparatus or observe color bands moving, the abstract concepts of boiling points and polarity become tangible and memorable.

• National Curriculum Attainment Targets
• KS3: Science - Pure and Impure Substances

• 25–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Inquiry Circle
• 35 min · Small Groups

Small Groups: Ink Chromatography Challenge

Provide filter paper, inks, and solvents like water or isopropyl alcohol. Students draw starting lines, add spots of ink, and suspend paper in solvent jars covered with cling film. They measure distances traveled by separated colors and calculate simple Rf values to compare inks.

Explain how distillation separates liquids with different boiling points.

Facilitation Tip

During the Ink Chromatography Challenge, remind groups to mark the solvent front immediately and to keep the paper from touching the sides of the jar to prevent uneven wicking.

What to look for

Present students with a diagram of a simple distillation apparatus. Ask them to label the key parts (flask, condenser, receiving flask) and write one sentence explaining what happens to the liquid with the lower boiling point.

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

Activity 02

• Inquiry Circle
• 40 min · Pairs

Pairs: Simple Distillation Apparatus

Use a hot water bath, test tube with colored water or dilute ethanol, delivery tube, and cold beaker for condensation. Pairs heat the mixture gently, collect distillate, and test purity with indicators. They record temperature changes and observe separation.

Analyze the principles behind chromatography for separating coloured substances.

Facilitation Tip

Before pairs begin the Simple Distillation Apparatus, check their setups for clamps and water connections so cooling is consistent across trials.

What to look for

Pose the question: 'Imagine you have a mixture of sand and salt water. Which separation technique, distillation or chromatography, would be more effective, and why?' Facilitate a class discussion where students justify their choices based on the properties of the substances.

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

Activity 03

• Inquiry Circle
• 45 min · Small Groups

Whole Class: Separation Technique Stations

Set up stations for filtration review, chromatography, distillation demo, and evaporation. Classes rotate, performing quick tests on mixtures like sand-salt-water-ink. Students note pros and cons of each method in shared charts.

Design an experiment to separate a mixture of ink colours using chromatography.

Facilitation Tip

At Separation Technique Stations, assign each pair a 6-minute rotation timer and a single shared notebook page for recording observations to build comparative data quickly.

What to look for

Provide students with a chromatogram showing separated ink colours. Ask them to identify which ink colour travelled the furthest and explain why this happened in terms of solubility and attraction to the paper.

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

Activity 04

• Inquiry Circle
• 25 min · Individual

Individual: Experiment Design Worksheet

Students plan a chromatography test for food dyes or a distillation for saltwater. They list materials, steps, variables, and predictions. Pairs then share and trial one design with teacher approval.

Explain how distillation separates liquids with different boiling points.

Facilitation Tip

During the Experiment Design Worksheet, provide colored pens so students can sketch their own distillation or chromatography setups with clear labels before building them.

What to look for

Present students with a diagram of a simple distillation apparatus. Ask them to label the key parts (flask, condenser, receiving flask) and write one sentence explaining what happens to the liquid with the lower boiling point.

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

A few notes on teaching this unit

Model each procedure first, then circulate to listen for misconceptions in real time. Avoid long lectures; instead, use students’ own observations to drive explanations. Research shows that concrete, hands-on experiences followed by immediate discussion help students build accurate mental models of phase changes and intermolecular forces.

Students will demonstrate understanding by correctly predicting which technique to use, explaining why substances separate, and adjusting their methods when results do not match predictions. Clear labeling of diagrams and coherent written explanations show mastery of key vocabulary and processes.

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Watch Out for These Misconceptions

• During the Simple Distillation Apparatus activity, watch for students who assume all liquids in the mixture boil at the same temperature.

  Have pairs record the temperature every 30 seconds and compare it to the known boiling points of the liquids. When the first liquid vaporizes, ask them to describe the trend in their data and relate it to molecular behavior.

• During the Ink Chromatography Challenge, watch for students who think dyes separate only by color size.

  Prompt groups to check the solvent front and the position of each band. Ask them to explain why two differently colored dyes might travel the same distance, tying observations to solubility and paper adhesion.

• During the Simple Distillation Apparatus activity, watch for students who believe distillation creates new substances.

  Collect the distillate in a clean test tube and have pairs test its pH and smell against the original mixture. Guide them to conclude that the distillate properties match one original component, not a new one.

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Methods used in this brief

• Inquiry Circle