This project experiment is suitable for secondary school pupils, aged 12-13. It includes illustration of various separating techniques, question for students and an example of experimental worksheet.
Mixtures can be separated into their constituents by using physical methods (i.e. no chemical reaction involved). Separation techniques are physical methods. Which technique to use depends on the different properties of the constituents. That is, different states, solubility, boiling and melting points.
Below lists some of the most common separation techniques:
Chromatography - To separate different coloured dyes. The dyes travel up the chromatography paper at different distances before they cannot remain in solution. The more soluble dyes move further up than the less soluble ones, hence separating from each other.
Distillation - to separate and collect a liquid from a solution of a soluble solid. The solution is heated in a flask until the liquid boils. The vapour produced passes into the condenser where it is cooled and condenses to a liquid. The pure liquid (distillate) is collected in a beaker.
Evaporation - This method is suitable to separate a soluble solid from a liquid. If the solution is heated, the liquid evaporates leaving the solid behind.
Fractional Distillation - This is a special type of distillation used to separate a mixture of liquids. Different liquids boil at different temperatures. When heated, they boil off and condense at different times. The apparatus features a fractionating column, which ensures that only the liquid boils at its boiling point will pass into the condenser.
Filtration - To separate an insoluble solid from a liquid. The solid remains in the filter paper and the liquid goes through the paper into the beaker.
Some of the example mixtures that can be separated using the above mentioned techniques:
(1) separating dyes in inks, or chlorophyll in plants (ethanol as solvent) - chromatography;
(2) separating sand from water - filtration;
(3) separating ethanol and water - fractional distillation;
(4) separating water from ink - simple distillation;
(5) separating salt from water - evaporation