Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Chemistry
Lesson Topic: Describe how paper chromatography is used to separate mixtures of soluble colourless substances, using a suitable solvent and a locating agent
Learning Objective/s:
  • Describe the principle of paper chromatography and the roles of the stationary and mobile phases.
  • Calculate retention factor (Rf) values for separated components.
  • Select an appropriate solvent system and locating agent for colourless substances.
  • Carry out the paper chromatography procedure safely and accurately.
  • Interpret chromatograms to identify unknown substances.
Materials Needed:
  • Chromatography paper (filter paper)
  • Solvent (e.g., ethanol, water, or ethanol : water mixture)
  • Developing chamber (sealed container)
  • Pencil and ruler
  • Capillary tubes or micropipettes
  • Locating agents (iodine crystals, ninhydrin solution, UV lamp)
  • Safety equipment (gloves, goggles, lab coat)
 Introduction:
Begin with a short video showing colourful spots appearing on a paper strip, prompting students to wonder how invisible substances can be separated. Recall prior knowledge of solubility and capillary action. Explain that by the end of the lesson they will be able to carry out a paper‑chromatography experiment, calculate Rf values and interpret the results.
Lesson Structure:
  1. Do‑now (5'): Students answer quick questions on solubility and capillary action.
  2. Mini‑lecture (10'): Explain stationary/mobile phases, the Rf formula, and safety considerations.
  3. Demonstration (10'): Show set‑up of the chromatography strip, solvent level, and origin line.
  4. Guided practical (20'): Students cut paper, draw origin, spot sample, add solvent, and mark the solvent front.
  5. Locating‑agent activity (10'): Apply iodine vapour or ninhydrin, observe coloured spots.
  6. Data analysis & discussion (10'): Measure distances, calculate Rf values, compare with standards, discuss errors.
  7. Exit ticket (5'): Write one key thing learned and one remaining question.
Conclusion:
Summarise how paper chromatography separates components based on differential solubility and how Rf values aid identification. Students complete an exit ticket stating the most suitable solvent for a given mixture. For homework, research another locating agent and prepare a brief report on its application.