Lesson 8 of 8

Choosing a method

Goal: Choose the right technique to separate a mixture.

Puzzles for this lesson

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A beaker of cloudy water with sand at the bottom, next to a filter funnel, filter paper and an evaporating basin

To choose a method, ask what is different about the substances in the mixture.

FiltrationOne is an insoluble solid. The other is a liquid.
EvaporationA solid is dissolved, and you want the solid.
DistillationA solid is dissolved, and you want the liquid.
ChromatographySeveral coloured substances are dissolved together.

Some mixtures need two methods. For sand, salt and water: filter out the sand first, then evaporate the water to leave the salt.

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Key words in this lesson

Mixture Two or more substances mixed together, not joined

Insoluble Not able to dissolve

Filtration Separates an insoluble solid from a liquid

Evaporation A liquid turning into a gas

Distillation Evaporating a liquid and then condensing it

Chromatography Separates dissolved coloured substances

For teachers: AQA 3.5.2 · Pearson Edexcel 13.1