Chemistry-Separation Techniques

Simple distillation
Distillation involves two stages and both are physical state change.
Stage (1): The liquid or solution mixture is boiled to vaporise the most volatile component in the moisture. (liquid --> gas)
Stage (2): The vapour is cooled by water in the Liebig condenser to condense (gas --> liquid) it back to a liquid (the distillate) which is collected.

Crystallisation
-Crystallisation from solution is the most common method used to purify soluble solids.
-The seeding method allows you to grow a large single crystal, others allow you to grow many crystals at a time.
-By controlling the variables such as cooling rate and evaporation rate, the size and shape of the crystals can be controlled.
-Crystallisation is used to purify crystals and substances that decompose upon strong heating.

Decanting

Decanting is the process of pouring off a liquid leaving the precipitate(sediments) at the bottom of the container.

e.g. sugar solution

Decanting is used to separate a dense, insoluble solid from a liquid.

Filtration

-Filtration is used to separate a mixture of a solid and a liquid.

-Upon filtration, the solid that remains on the filter paper is called the residue. The liquid that passes through the filter paper is called the filtrate.

-Filtration can be used to separate two solids if only one of them is soluble in solvent.

-A magnet can be used to separate magnetic substances, from non-magnetic ones.

-Sublimation is used to separate a substance that sublimes from one with a high melting point.

Extra information

1. Substances that do not decompose on strong heating can be purified by evaporation to dryness.

2. A saturated solution can be produced by evaporation.