Filtration and Crystallisation

This lesson covers two essential separation techniques — filtration and crystallisation — as required by the Edexcel GCSE Chemistry specification (1CH0, Topic 1). You need to know when to use each technique, the practical method for each, and the scientific principles behind them. These techniques link directly to Edexcel core practicals, so you must be able to describe the methods in detail.

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Filtration

Filtration is used to separate an insoluble solid from a liquid (or a solution). The mixture is poured through filter paper, which has tiny pores that allow the liquid to pass through but trap the solid particles.

Key Vocabulary

Term	Definition
Residue	The insoluble solid that remains on the filter paper
Filtrate	The liquid that passes through the filter paper
Insoluble	Does not dissolve in a given solvent
Soluble	Dissolves in a given solvent

Apparatus Needed

• Filter paper
• Filter funnel
• Conical flask (to collect the filtrate)
• Beaker (containing the mixture)
• Retort stand and clamp (to hold the funnel)

Method