Separation Techniques

Text by Mrs Teo Video clips taken from school video repository

Instructions 1. You have learnt that a mixture is made up of components not chemically combined together. Thus the components can be separated by several methods. 2. Go through this lesson package on the various separation techniques. 3. Follow up by reading your textbook.

1. A mixture is made up of components not chemically combined together, e.g. ink, fizzy drinks, mineral water, crude oil, air 2. The components of a mixture can be separated by several methods or techniques. 3. Each separation technique makes use of differences in the physical properties of the components

The Different Separation Techniques are as follows: • Magnetic attraction • Filtration • Evaporation • Crystallisation • Distillation • Chromatography

Magnetic Attraction • used to separate magnetic materials, e.g. iron, steel, nickel, cobalt from non-magnetic ones in a mixture

e.g. separating iron filings from sulphur powder

Applications of Magnetic Attraction

1.Electromagnets are used to remove steel and iron scrap at the junk-yard. 2. In hospitals, magnets are often used

to remove iron splinters from a patient’s eyes.

Using a Separating Funnel • can be used to separate two

immiscible liquids, such as oil and water

http://vle.hci.edu.sg/chemistry/beijing/expt%20techniques/lesson5.html

Filtration

• used to separate (i) an insoluble solid from a liquid in a solid-liquid mixture e.g. sand from a mixture of sand and water

sand)

(water that passes through filter paper)

Filtration (ii) used to separate an insoluble solid from a soluble solid e.g. insoluble calcium carbonate from soluble copper(II) sulphate

•

Filtration • insoluble solid that remains on the filter paper - residue • liquid that passes through- filtrate

(filtrate can be water, any other solvent, or a solution)

Applications of Filtration • hair in our nostrils trap the dust particles that we breathe in and allow only clean air to pass through

• air filters in air conditioners remove solid impurities from air • oil and air filters in cars remove solid impurities found in engine oil and air

Evaporation to dryness • used to separate a dissolved solid (solute) that does not decompose on heating from a solution solution,,

e.g. common salt from a salt solution

Procedure of Evaporating a Solution 1. Pour the solution into an evaporating dish. 2. Heat the solution to dryness to evaporate away the solvent, leaving behind the solute. 3. Make the Bunsen flame smaller when almost all the solvent has been evaporated away to reduce spitting.

Applications of Evaporation • drying wet clothes • drying hair with a hair -dryer hair-dryer • obtaining common salt from the sea

Crystallisation • process to obtain a solid that decomposes on heating from its solution e.g. sugar crystals from sugar solution and copper(II) sulfate crystals from copper(II) sulfate solution

Procedure of Crystallisation 1. Pour the solution, e.g. copper (II) sulfate solution, into an evaporating dish. 2. Heat the solution to evaporate away the solvent until some solid starts to appear or a saturated solution is obtained. 3. Leave the solution to cool. 4. On cooling crystals of the solute that can no longer disssolve in the solution will be deposited as crystals. 5. Filter the mixture to collect the crystals which will be the residue.

Simple Distillation

• process used to separate a pure liquid (solvent) from a solid-liquid solution

e.g. pure water can be distilled from soft drinks, sea-water, etc

Distillation

Simple Distillation • solution boiled in distilling flask and vapour/steam cooled and condensed in a Liebig condenser • condenser consists of jacket of cold water with coldest

water entering bottom of jacket and circulating out through the top ensuring that coldest part of condenser is just before the vapour escapes and that the jacket is completing full of water • condensed solvent – distillate • all impurities left in distilling flask • anti-bumping granules/boiling chips/beads-ensure even boiling

Fractional Distillation • process can be used to separate

miscible liquids with different boiling

points

• liquid with lower boiling point will vaporise first e.g. to separate alcohol and water

Fractional Distillation

Industrial Applications of Fractional Distillation

• oil refineries - separating the various components of

crude oil or petroleum

Industrial Applications of Fractional Distillation industries supplying oxygen to hospitals, shipyards, etc •

– separating the

components of air

Paper Chromatography • process used to separate the different components in a liquid mixture For example it can be used 1. to separate the different coloured components that make up black ink 2. to detect tiny amounts of drugs or certain other chemicals in urine samples

Paper Chromatography 1. Apply a small but concentrated spot of the solution on a piece of chromatography paper. 2. Suspend the chromatography paper in a beaker or boiling tube of solvent with the spot above the level of the solvent.

Paper Chromatography 3. Separation takes place because some components of the liquid mixture travel at a faster pace than other components on the paper or any other absorbent material.

Paper Chromatography 3. As the solvent travels up the paper, the mixture is separated into its respective components. A chromatogram of the separated components is obtained. YouTube video clip

Applications ••analysing analysing ink dyes for forgery cases ••analysing analysing food dyes to ensure that only permitted colourings are used in foodstuffs •checking whether pesticides on vegetables exceed safe levels ••detecting detecting trace levels of drugs in urine samples

Sublimation - process by which a substance changes from solid state to vapour state on heating - e.g of substances which sublime - iodine - ammonium chloride On heating, they do not melt. Iodine changes into a beautiful violet vapour while ammonium chloride changes into a white vapour. They change back into solid crystals on cooling.

Sublimation - process used to separate a solid that sublimes from one that does not e.g. iodine or ammonium chloride from common salt

Sublimation When a mixture of a solid that sublimes and a solid that does not is heated, the solid that sublimes will turn into a vapour and separates from the other solid which remains in the container.

The End

ACE Suggestions 1. Production of whisky by distillation of barley mash

ACE Suggestions 2. Commercial Production of sodium chloride by: (i) Mining

(ii) Evaporation of sea water