• This is used to separate a liquid and?soluble solid?from a solution (e.g., water from a solution of salt water) or a pure liquid from a mixture of liquids
• The solution is heated, and pure water evaporates producing a vapour which rises through the neck of the round bottomed flask
• The vapour passes through the condenser, where it cools and condenses, turning into the pure liquid that is collected in a beaker
• After all the water is evaporated from the solution, only the solid solute will be left behind

Diagram showing the distillation of a mixture of salt and water

• This is used to separate two or more liquids that are?miscible?with one another (e.g., ethanol and water from a mixture of the two)
• The solution is heated to the temperature of the substance with the lowest boiling point
• This substance will rise and evaporate first, and vapours will pass through a condenser, where they cool and condense, turning into a liquid that will be collected in a beaker
• All of the substance is evaporated and collected, leaving behind the other components(s) of the mixture
• For water and ethanol
  • Ethanol has a boiling point of 78 oC and water of 100 oC
  • The mixture is heated until it reaches 78 oC, at which point the ethanol boils and distills out of the mixture and condenses into the beaker

   

• When the temperature starts to increase to 100 oC heating should be stopped. Water and ethanol are now separated

Fractional distillation of a mixture of ethanol and water

• Used to separate an?undissolved solid?from a mixture of the solid and a liquid / solution ( e.g., sand from a mixture of sand and water)
  • Centrifugation can also be used for this mixture

   

• A piece of filter paper is placed in a filter funnel above a beaker
• A mixture of insoluble solid and liquid is poured into the filter funnel
• The filter paper will only allow small liquid particles to pass through as filtrate
• Solid particles are too large to pass through the filter paper so will stay behind as a residue

Filtration of a mixture of sand and water

• Used to separate a?dissolved solid?from a solution, when the solid is much more soluble in hot solvent than in cold (e.g., copper sulphate from a solution of copper (II) sulphate in water)
• The solution is heated, allowing the solvent to evaporate, leaving a saturated solution behind
• Test if the solution is saturated by dipping a clean, dry, cold glass rod into the solution
  • If the solution is saturated, crystals will form on the glass rod

   

• The saturated solution is allowed to cool slowly
• Crystals begin to grow as solids will come out of solution due to decreasing solubility
• The crystals are collected by filtering the solution, they are washed with cold distilled water to remove impurities and are then allowed to dry

Diagram showing the process of crystallisation

• This technique is used to separate substances that have?different?solubilities?in a given solvent (e.g., different coloured inks that have been mixed to make black ink)
• A?pencil?line?is drawn on chromatography paper and spots of the sample are placed on it. Pencil is used for this as ink would run into the chromatogram along with the samples
• The paper is then lowered into the solvent container, making sure that the pencil line sits?above?the level of the solvent, so the samples don’t wash into the solvent container
  • The paper is called the?stationary phase
• The solvent travels up the paper by?capillary action, taking some of the coloured substances with it; it is called the?mobile phase
• Different substances have different solubilities so will travel at different rates, causing the substances to spread apart
  • Those substances with higher solubility will travel further than the others

   

• This will show the different components of the ink / dye
• If two or more substances are the same, they will produce identical chromatograms
• If the substance is a mixture, it will separate on the paper to show all the different components as separate spots
• An impure substance will show up with more than one spot, a pure substance should only show up with one spot

Analysis of the composition of ink using paper chromatography