Separating a Mixture

Paper Chromatography

• A pencil line is drawn near the bottom of the paper and a spot of ink is put on the line
• paper is put into a beaker with solvent
• make sure pencil line isn't in solvent otherwise risk of it dissolving
• place lid on beaker so solvent won't evaporate
• solvent will seep through paper carrying ink with it
• different dye within ink will more at different rates so the dye will separate
• if dye is insoluable it will stay at the bottom
• when all dyes have separated, take paper out to dry
• end result is a chromatogram

Filtration

• Used on insoluable solids and liquids to separate them
• However if a solid is soluable then there are two methods to separate the mixture- evaporation and crystallisation

Evaporation

• Pour solution into evaporating dish
• gently heat the solution
• solvent will evaporate and solution gets more concentrated
• crystals will form
• really quick way of separating salt from solution but only if salt doesn't decompose upon heating.

Crystallisation

• pour solution into evaporating dish and gently heat solution
• some solvent will evaporate and solution will get more concentrated
• when crystals start to form, remove from heat and leave to cool
• the salt will form crystals as it becomes insoluable
• filter crystals out of solution and leave to dry

Distillation

• used for filtering liquids
• solution is heated and the liquid with lower boiling point will evaporate into a tube
• vapour condenses and is collected in a beaker
• can only be used to separate liquids with very different boiling points so no mixing occurs

Fractional Distillation

• put mixture of liquids into a flask and put fractioning column on top
• different liquids will have different boiling points so they will evaporate at different temperatures
• match temperatures to lowest boiling point and wait till every bit has evaporated and has been collected
• repeat until all liquids have been separated.