How can chromatography separate and identify substances in mixtures?
Activities Remind pupils of work they did earlier on showing whether a liquid was pure or not. Explain that they are going to explore some other techniques for this. Demonstrate how to separate the different coloured compounds in an ink mixture on blotting or filter paper, using a wick of the paper dipped into the solvent (water). Discuss and establish with pupils why different coloured ink solids travel different distances, perhaps using the analogy of the solvent particles giving the solute particles ‘piggyback rides’, so those which attach more firmly to the solvent particles can be carried further than those which do not, in a given amount of time. Outcomes use chromatography to separate and identify different solutes use particle ideas to explain how chromatography works Objectives that a mixture of two or more solutes which are soluble in a particular solvent can be separated by chromatography to separate and identify materials using chromatography Points to note Extension: pupil
