Separation Techniques

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Separation Techniques

  1. 1.  A pure substance is made up of only onesubstance and is not mixed with any othersubstance. A mixture is a substance that contains two ormore substances that are not chemicallycombined. Purity of a substance can determined bytesting its melting and boiling points orchromatography.
  2. 2. FIXED BOILING POINT FIXED MELTING POINT A pure solid will meltcompletely at a fixedtemperature. Impurities lower themelting point of asubstances. Impurities causemelting to occur over arange of temperatures. A pure solid will boil atan exact and fixedtemperature. Impurities higher theboiling point of asubstances. Impurities causeboiling to occur over arange of temperatures.
  3. 3. Separation method What it separatesChromatography Compounds in a solution with same propertiesFiltration Solids or group of solids and liquids in a mixtureEvaporation Solids that cannot decompose when heated in a solutionCrystallisation Dissolved solids in a solutionSimple Distillation Liquids in a solutionFractional Distillation Mixture of miscible (dissolved) liquidsSeparating Funnel Immiscible (undissolved) liquidsSublimation Substances that sublime from two substancesMagnetic Attraction Magnetic substances from non-magnetic ones
  4. 4. Separation method Differences between objectsChromatography Solubility with ethanolFiltration Size of particlesEvaporation State of object (solid and liquid)Crystallisation State of object (solid and liquid)Simple Distillation Boiling pointsFractional Distillation Boiling pointsSeparating Funnel Both are immiscibleSublimation Ability to sublimeMagnetic Attraction Magnetism
  5. 5. Chromatography Apply a spot of food colouring to thechromatography paper. Dip the chromato-graphy paper in ethanol. Ethanol dissolves the dyes and travels up thepaper, carrying the dyes along. Coloured spots are left in different places ofthe paper depending on the solubility of thedye in ethanol.
  6. 6. Filtration Place a piece of filter paper in a filter funnel.Position a beaker under the filter funnel. Pour the mixture into the filter funnel.Theliquid passes through the filter paper while theinsoluble solids does not pass through. The filtrate will be collected in the beaker andthe residue remains on the filter paper. Wash the residue with distilled water and let itdry. Separation is complete.
  7. 7. Filtration Place a piece of filter paper in a filter funnel.Position a beaker under the filter funnel. Pour the mixture into the filter funnel.Theliquid passes through the filter paper while theinsoluble solids does not pass through. The filtrate will be collected in the beaker andthe residue remains on the filter paper. Wash the residue with distilled water and let itdry. Separation is complete.
  8. 8. Crystallisation Crystillisation applies to all substances whileevaporation applies to substances that do notdecompose when heated strongly. Set up an apparatus of a beaker of the solution. Apply heat under the beaker with a bunsenburner until a hot saturated solution is formed. The solution is allowed to cool and the mixtureis then filtered. Separation is complete.
  9. 9. Simple Distillation Place a distillation flask under a bunsen burnerand connect it to a condenser. Cold runningwater is allowed to enter from the bottomcondenser and leave from the top. Allow the condenser to slope downwardstowards a beaker where the distillate iscollected. Heat a distillation flask with the solutiontogether with porcelain chips until it boils. Pure solvent is collected in the beaker.
  10. 10. Fractional Distillation Place a distillation flask under a bunsen burnerand connect it to a fractional column.The fractionalcolumn is connected to a condenser. Cold running water is allowed to enter from thebottom condenser and leave from the top. Allow the condenser to slope downwards towards abeaker where the distillate is collected. Heat a distillation flask with the mixture togetherwith porcelain chips until it boils. The miscible liquid with a lower boiling point iscollected.
  11. 11. Separating funnel Pour the mixture into the separating funnel. Support the separating funnel using a retortstand and place the beaker below the funnel. Allow the liquids to separate completely.Thedenser liquid will fall to the bottom. Open the tap of the funnel to allow the bottomlayer to drain into the beaker. Close the tap when the liquid is fully drained. Place another beaker below the funnel tocollect a little of the top layer liquid so that theliquids are fully separated.
  12. 12. Sublimation Place the mixture in an evaporating dish.Position the dish under a bunsen burner. Place an inverted funnel just above the dish. The substance with high melting point wouldbe left on the dish. The other substance will vapourise andsolidify when it lands on the surface of thefunnel.
  13. 13. Magnetic attraction Place the mixture of magnetic and non-magnetic objects in a dish. Place a magnet directly above the dish. Magnetic objects will be attracted to themagnet while non-magnetic objects will be lefton the dish.
  14. 14. Separation method Common usesChromatography • Identify coloured substances used food products• Identify if foods contain banned dyesFiltration • Separating sand from water• Human nose traps dust and allows oxygen to passCrystallisation • Separating salt from salt waterSimple Distillation • Separating water from salt water in desalination
  15. 15. Separation method Common usesFractional Distillation • Separate petrol, kerosene and diesel from petroleum• Obtain nitrogen, argon and oxygen from airSeparating Funnel • Separate oil and waterSublimation • Separate iodine from sandMagnetic Attraction • Recycling magnetic materials by separating themfrom domestic waste

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