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.

• Year 7
• Science
• 4 activities
• 25 min–45 min

Learning Objectives

1. Explain the physical principles that allow distillation to separate liquids with different boiling points.
2. Analyze the process of chromatography, identifying how different substances separate based on solubility and affinity.
3. Design a step-by-step experimental procedure to separate a mixture of ink colours using paper chromatography.
4. Compare the effectiveness of distillation and chromatography in separating different types of mixtures.

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.

Prepare & details

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.

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·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.

Prepare & details

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.

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

⏱ 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.

Prepare & details

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.

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

⏱ 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.

Prepare & details

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.

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

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.

What to Expect

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.

Watch Out for These Misconceptions

Common Misconception

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

What to Teach Instead

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.

Common Misconception

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

What to Teach Instead

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.

Common Misconception

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

What to Teach Instead

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.

Assessment Ideas

Quick Check

After the Simple Distillation Apparatus, show students a labeled diagram with missing condenser and receiving flask. Ask them to fill in the labels and write one sentence explaining what happens to the liquid with the lower boiling point.

Discussion Prompt

After Separation Technique Stations, pose the question: 'Which technique would you choose to separate sand from salt water, and why?' Facilitate a class discussion where students defend their choices using evidence from their station observations.

Exit Ticket

During the Ink Chromatography Challenge, ask students to hand in their chromatograms with the farthest-traveling color circled and a one-sentence explanation connecting solubility to distance traveled.

Extensions & Scaffolding

• Challenge early finishers to separate a mixture of food coloring and salt water using both techniques, then compare the purity of the distillate and the chromatogram.
• Scaffolding for struggling students: Provide pre-labeled diagrams of each apparatus stage and sentence stems like 'The substance with the _____ boiling point vaporized first because...'.
• Deeper exploration: Ask students to research how fractional distillation is used in industry to separate petroleum and present a one-slide summary to the class.

Key Vocabulary

Distillation	A separation technique that involves boiling a liquid and then condensing the vapor to collect a purer substance, based on differences in boiling points.
Boiling Point	The temperature at which a liquid turns into a gas at a given pressure. Different substances have unique boiling points.
Chromatography	A technique used to separate mixtures of soluble substances, often coloured ones, by passing them through a stationary phase using a mobile phase.
Stationary Phase	The immobile component in chromatography, such as the paper or a solid coating, that substances interact with.
Mobile Phase	The moving component in chromatography, typically a liquid solvent or gas, that carries the mixture components through the stationary phase.