Chromatography separation is the focus of this Grade 7 Science resource on Pure Substances and Mixtures, guiding students through how stationary and mobile phases separate substances and how molecular polarity influences movement. Students connect chromatographic patterns to identification, retention factors, purity, and the practical limits of purification.

The lesson explains the roles of stationary phase, mobile phase, adsorption, polarity, and partitioning in paper chromatography. Students examine why a compound that interacts more strongly with the solvent can travel farther, while stronger attraction to the paper can hold a substance back. The resource also introduces resolution and why distinct spots matter when individual components need to be separated or collected.

From Chromatograms to Evidence

A key focus is interpreting retention factor (Rf). Students work with the relationship between the distance traveled by a compound and the distance traveled by the solvent front, then use Rf values to compare unknown substances with reference materials. An extended ink-sample scenario asks students to reason from matching and non-matching Rf values while considering a limitation that could affect interpretation.

The chromatography worksheet includes a reading passage followed by multiple-choice questions, true-or-false statements, short-answer questions, matching, a cloze exercise, an extended response, and a Did You Know section. Tasks address stationary and mobile phases, adsorption, molecular polarity, Rf interpretation, reference substances, resolution, overlapping spots, and limitations such as insufficient separation or irreversible sticking.

What the Teacher Receives

• ✅ Student worksheet focused on chromatography separation and retention
• ✅ Separate Answer Key PDF for checking student responses
• ✅ Student Notes & Lesson Summary supplement for review and reinforcement
• ✅ Teacher Guide with Learning Objectives, Teaching Tips, Discussion Questions, and Common Mistakes

Use this Grade 7 Science activity for direct instruction support, guided reading, independent practice, review, or consolidation within a Pure Substances and Mixtures lesson. The structured progression moves from the mechanism of chromatography to interpreting evidence, allowing students to apply vocabulary and reasoning rather than simply memorize definitions.

For Ontario Science classrooms, this resource provides a focused way to teach paper chromatography, Rf values, polarity, chromatogram interpretation, and purity assessment. Its combination of conceptual reading, evidence-based questions, calculation practice, and extended reasoning gives teachers multiple ways to check whether students can explain why substances separate and evaluate what chromatographic results can—and cannot—show.