Mixtures Separation Techniques

How to separate suspensions?

Filtration with a filter funnel and filter paper.

How to separate solutions?

Several different ways including: filtration, sedimentation, flotation, centrifuging, magnetic separation, evaporation, crystallisation, decantation, distillation (fractional & simple) and chromatography.

Filtration

Can be used to separate suspensions as the particles are large enough to be retained by the filter paper, while the smaller liquid particles will pass through the tiny holes in the paper.

Sedimentation

A separation technique that is demonstrated by allowing sediment to settle to the bottom of the mixture, and can thus be separated from the mixture. Flocculant may be added to make suspended particles clump together.

Flotation

A separation technique in which a substance will float to the top of a liquid because it is less dense.

Centrifuging

A separation technique used to separate light particles from heavy particles by rapidly spinning a mixture in a container. The spinning motion causes the heavier particles to move to the bottom of the mixture. 

E.g. blood

Magnetic Separation

Using a magnetic material to separate magnetic materials from non-magnetic ones.

Evaporation

A separation technique used to separate the solute from the solvent.

Crystallisation

A separation technique used in conjunction with evaporation to remove a dissolved solid from a liquid; after the liquid has been evaporated, the solid remains, often in the form of small crystals.

E.g. salt and water

Decantation

A separation technique used to separate a sediment/less dense liquid from a denser liquid by carefully pouring the top liquid away. 

E.g. water and oil

Distillation

A separation technique that uses evaporation and condensation to separate a solid and the solvent in which it has dissolved.

E.g. pure water from salt water

Fractional vs Simple (Distillation)

Fractional distillation is used when the components have close boiling points, and simple distillation is used when the boiling points are significantly different.

E.g. ethanol and water

Chromatography

A separation technique used to separate colours according to their rates of movement along a surface. 

E.g. coloured dyes in pen ink