Return to site

GCSE Chemistry Booster Tutor: Separating Mixtures.

Techniques to separate useful substances.

· GCSE Science Notes

Many useful materials we use today are mixtures. There are many methods of separating mixtures including filtration, crystallisation, distillation, and chromatographic techniques. 

EVAPORATION (Crystallisation) will separate a soluble solute from a solvent. Crystallisation is the process by which a solid forms, where the atoms or molecules are highly organized into a structure known as a crystal. A common way in which crystals form are precipitating from a solution.


broken image


DISTILLATION will separate a soluble solute from a solvent but in this case the solute and the solvent can be captured. 


broken image


Distillation involves the evaporation of the solvent from the solute. As the steam moves into the condenser it cools and condenses back to water and can be captured into the beaker. The solute will remain in the round bottomed flask. 


FRACTIONAL DISTILLATION is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. 

broken image

When heated the vapours rise up the fractionating column. As they do so they cool and condense.

Different fractions of the mixture will boil at different temperatures. With fractional distillation it is possible to collect all the fractions as their boiling point is reached. 


Paper chromatography is used to separate a mixture of two soluble substances. It can be used to distinguish between pure and impure substances. Examples are inks and food dyes. 

Paper chromatography involves a stationary phase and a mobile phase. The mobile phase is the solvent, and it is absorbed by the stationary phase, the chromatography paper. As the mobile phase moves up the stationary phase the solvent dissolves the ink and separates the colours. 


broken image


The separation by chromatography produces a chromatogram.  

A pure substance will produce one spot on a chromatogram. An impure substance will produce two or more spots on a chromatogram.