1.7 describe experimental techniques for the separation of mixtures, including simple distillation, fractional distillation, filtration, crystallisation and paper chromatography

1.7 •simple distillation: •to separate a liquid from a solution e.g water from sodium chloride

                                     •the lowest boiling point of the solution boils first, cools and condenses 

                                     •can only separate a mixture of liquids with very different boiling points

      

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        •fractional distillation: •to separate a mixture of solutions 

                                           •different substances have different boiling points and so will condense at different temperatures

                                           •they therefore condense at different times as the mixture travels up the tube the temperature decreases, substances begin to condense

                                           •when the first liquid has been collected, you raise the temperature 

        •filtration: •to separate undissolved solid from a mixture of the solid and liquid 

                        •you use filter paper in a funnel in a beaker

      •crystallisation: •to separate a dissolved solid from a solution 

                               •some solvent will evaporate and the solution will get more concentrated and stop heating when crystals are formed

                               •leave in a dry place for big crystals

                               •dry the product using a drying oven 

      •paper chromatography: •to separate substances that have different solubilities in a solvent 

                                             1. •draw a line at the bottom of a sheet of filter paper in pencil 

                                             2. •add spots of different dye at regular intervals 

                                             3. •loosely roll the sheet and place in a beaker of water

                                              •make sure the dyes aren't touching the solvent and seal the beaker

                                              •each dye will move up at a different rate and will form a spot there