Separation Methods AQA Triple Science Chemistry

  • Created by: MaganjotC
  • Created on: 16-04-19 16:16

Chromatography

Chromatography separates compounds out of a mixture.

1. draw a line near the bottom of the sheet in pencil

2. add a spot of ink on the line and add the sheet to the beaker of solvent 

3. make sure the ink isn't touching the solvent 

4. the different colours should make their way up the paper

5. once all the colours have separated, take the paper out to dry

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Filtration and Crystallisation

They are methods of seperating mixtures. Filtration seperates insoluble solids from liquids.

Two ways to seperate soluble liquids from solutions - evaporation and crystallisation.

evaporation - pour solution into evaporating dish, heat evaporating dish which will evaporate the liquid and form crystals, repeat until there are only dry crystals remaining.

crystallisation - pour soution into evaporating dish and gently heat, once some solvent has evaporated leave the dish to cool, salt should form crystals as it becomes insoluble in acold highly concentrated solution, filter the crystals and leave them to dry. 

Both can be used to separate rock salt 

1. grind the mixture to make the salt smaller

2. put the mixture in water to dissolve the salt  

3. filter the mixture, the salt will filter but the sand won't

4. evaporate the water so you are left with just the salt (crystallisation can also be used here)

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Distillation

Simple Distillation is used to separate out solutions. 

the solution is heated, the part of the solution with the lowest boiling point evaporates first. the vapor is then cooled, condenses and is turned back into a liquid. The rest of the solution is left in the flask. The problem with simple distillation is that you can only use it to seperate liquids with very different boiling points. 

Fractional Distillation is used to separate mixtures of liquids which have boiling points that are close together. 

Put mixture in a flask and stick a fractionating column on top and heat it. The different liquids will have different boiling points so they will evaporate at different temperatures. The liquid with the lowest boiling point will evaporate first and it will get sent to the top of the column. Once the first liquid is condensed, raise the temperature until the next one is separated out.

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