Identifying Pure Substances

Key Stage 3

Meaning

Identifying Pure Substances is a set of methods that can be used to determine if a substance is a mixture of other substances or whether it is pure.

About Identifying Pure Substances

To identify if a substance is pure the experimenter should try several separation techniques.

To find if a liquid is pure:

1. Filter the substance. If a residue is left in the filter paper, then the substance is not pure.

2. Distill the substance. If a material is left behind during distillation then it is not pure.

To find if a solid is pure:

1. Dissolve the solid in a solvent.

2. Place a drop of the solution on chromatograph paper and use the same solvent to complete a chromatography experiment. If two or more separate patches appear, then it is not pure.