Science · Grade 7

Active learning ideas

Chromatography

Active learning works for chromatography because students must observe real-time changes, compare results, and adjust their understanding as colors separate. Handling materials directly shows how solubility and adhesion interact, turning abstract concepts into visible evidence. This hands-on approach builds lasting understanding better than passive notes or diagrams alone.

• Ontario Curriculum Expectations
• MS-PS1-2

• 30–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Experiential Learning
• 45 min · Small Groups

Lab Rotation: Ink Separation Stations

Prepare stations with filter paper, black markers, water, and alcohol solvents. Students spot ink at the base, place paper in solvent jars, and measure pigment distances after 20 minutes. Groups rotate to compare solvents and record Rf values.

Explain how chromatography separates components of a mixture.

Facilitation Tip

During Lab Rotation: Ink Separation Stations, circulate with guiding questions like, 'What do you notice about the colors that moved the farthest? How does the solvent’s speed compare to the ink’s?' to prompt deeper observation.

What to look for

After students complete a paper chromatography experiment, ask them to draw their results and label the different colors they observe. Then, ask: 'Which color traveled the furthest and why?'

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

Activity 02

• Experiential Learning
• 35 min · Pairs

Pairs Challenge: Plant Pigment Chromatography

Pairs crush spinach leaves in alcohol, spot extract on paper, and run chromatography. They identify chlorophyll bands by color and distance traveled. Discuss how solubility affects separation rates.

Analyze how different pigments in ink can be separated using paper chromatography.

Facilitation Tip

For Pairs Challenge: Plant Pigment Chromatography, provide a data table for students to record pigment distances and colors before discussing why spinach and carrot pigments travel differently.

What to look for

Pose the question: 'Imagine you are testing a new type of marker. How would you use chromatography to determine if it is a pure substance or a mixture? What would you expect to see if it were a mixture?'

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

Activity 03

• Experiential Learning
• 30 min · Whole Class

Whole Class: Solvent Prediction Demo

Display three solvents; class predicts separation of candy dyes on paper strips. Run demos simultaneously, then vote and measure results. Debrief on adhesion and solubility patterns.

Predict how changing the solvent might affect the separation in chromatography.

Facilitation Tip

In Whole Class: Solvent Prediction Demo, ask students to vote on which solvent they think will work best for each ink type before testing, then revisit predictions after results appear.

What to look for

Provide students with a scenario: 'A student used water as a solvent for black ink and alcohol as a solvent for blue ink. Both inks separated into multiple colors. What is one difference you might expect between the two results, and why?'

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

Activity 04

• Experiential Learning
• 40 min · Individual

Individual: Mystery Mixture Analysis

Provide unknown ink mixtures; students run chromatography alone, sketch results, and identify components by matching known samples. Share findings in a gallery walk.

Explain how chromatography separates components of a mixture.

Facilitation Tip

During Individual: Mystery Mixture Analysis, give students a reference sheet of known pigments to help them identify components in unknown samples.

What to look for

After students complete a paper chromatography experiment, ask them to draw their results and label the different colors they observe. Then, ask: 'Which color traveled the furthest and why?'

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

A few notes on teaching this unit

Teachers should emphasize that chromatography is a model for separation science, not just a color experiment. Avoid rushing to conclusions by encouraging students to repeat trials when bands appear uneven. Research shows that students grasp polarity better when they test multiple solvents and compare results side by side, so plan at least two solvent options per activity. Use student-generated data to co-create a class definition of solubility and adhesion during wrap-up discussions.

Successful learning looks like students accurately predicting which pigments will travel fastest based on solvent choice and explaining why mixtures separate into bands. They should use precise vocabulary like solubility and adhesion when discussing results and link observations to the separation process. Small-group discussions should include comparisons between different ink and plant pigment samples.

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Watch Out for These Misconceptions

• During Lab Rotation: Ink Separation Stations, watch for students assuming each ink color is a single pure substance. Redirect them by asking, 'How many distinct bands do you see in your black ink sample? What does that suggest about its composition?'

  After students observe multiple bands in black ink, have them compare their results to the pure colors in other markers. Ask, 'What evidence shows that inks are mixtures rather than pure substances?'

• During Whole Class: Solvent Prediction Demo, watch for students believing all solvents work equally well for every ink. Redirect by asking, 'Which solvent moved the ink fastest? Why might water work better for some inks than alcohol?'

  During the demo, pause after each solvent to ask groups to explain why certain pigments moved faster. Record class observations on a board to highlight solvent-pigment interactions.

• During Pairs Challenge: Plant Pigment Chromatography, watch for students attributing separation solely to the size of pigment molecules. Redirect by asking, 'Why did the yellow pigment travel farther than the green, even though they are both small molecules?'

  After the activity, have students sort their results into two categories: pigments that traveled far and those that didn’t. Ask them to explain each category using the terms solubility and adhesion.

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Methods used in this brief

• Experiential Learning