Physical separation techniques (ONLY FOR MIXTURES)

• Filtration is used to separate an insoluble (Not dissolving) solid from a liquid.
• Filtration method- We need a filter funnel and filter paper. Start by pouring the mixture into the filter paper. The liquid then simply passes through the tiny pores in the filter paper. However, the solid material cannot pass through the filter paper and so therefore in the end we have our liquid separated from our solid.
• Crystallisation is used to separate a SOLUBLE (dissolvable) solid from a liquid
• Crystallisation Method - Firstly add some water or alcohol to your solution. Then heat it up until all the solute has dissolved. Once this happens cool down the solution slowly. This causes the solvent to change state from a liquid to a solid. As the temperature decreases more and more of the solute will come out of solution as crystals. These can be filtered off using a filter funnel and filter paper
• Simple distillation is used to separate a liquid from a solid if we want to keep the liquid.
• Simple Distillation Method – Fill the flask with the mixture. Heat the flask gently on a Bunsen burner. When the mixture starts boiling collect the vapour that rises above the flask in a condenser tube. Cool the condenser tube with cold tap water. Collect the condensed liquid in a test tube. If there are any impurities they will remain behind in the original flask.
• In Fractional distillation we separate a mixture of different liquids. These liquids must have different boiling points
• Fractional distillation method involves filling a round bottomed flask with the mixture, placing the flask onto a ring stand, connecting the flask to a fractionating column, attaching the top of the column to a condenser tube, and finally connecting the other end of the condenser tube to a receiver flask.
• Heating the mixture at the base of the flask causes the hotter parts of the mixture to evaporate first, rise up the column, and cool back to a liquid.
• Each component of the mixture will condense at its own specific temperature, so when one part of the mixture reaches its boiling point it will start to drip down the side of the column into the receiver flask below.
• In this way, pure fractions of each individual component of the mixture are obtained.
• In fractional distillation if the liquids have got a very similar boiling point then it is much harder to separate them and we may have to carry out several rounds of fractional distillation.
• Paper chromatography allows us to separate substances based on their different solubilities.
• The paper used in paper chromatography is called the stationary phase as it does not move
• The solvent in paper chromatography is called the mobile phase as it does move
• A pure chemical will produce a single spot in all solvents. The chemicals in a mixture may separate into different spots depending on the solvent.
• In paper chromatography why do we draw our starting line in a pencil?

  If we drew the line in pen, the pen ink would move up the paper, with the solvent