Seperation Techniques: Methods

  • Created by: Bulberman
  • Created on: 08-11-18 19:58

Evaporation

1)Pour the solution into an evaporating dish.
2)Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually crystals will start to form.
3)Keep heating the evaporating dish until the only thing left are dry crystals.

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Crystallisation

1)Pour the solution into an evaporating dish and gently heat it. Some of the solvent will vaporate.
2)Once the solvent has started evaporating/You see crystals start to form(known as the point of crystallisation), remove the dish and leave the solution to cool.
3)Salt should start to form crystals as it becomes insoluble in the cold.
4)Filter the crystals out and leave them in a warm place to dry for example a drying oven or a desiccator.

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Simple Distillation

Simple distillation is used to seperate a liquid from a solution.

1)The solution should be heated. The part of the solution with the lowest boiling point should evaporate first.
2)The vapour then cools and condenses and is collected.
3)The rest of the solution is left behind.
Fact:You can use simple distillation to get pure water from sea water as the water evaporates and is condensed and eventually the only thing left in the flask is the salt.
Disadvantage: You can only use it seperate things with very contrasting different boiling points, if the boiling poins are too similar the substances will mix together again which is bad. This can be solved by using fractional distillation

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Fractional Distillation

If you have a mixture of liquids you want to seperate you can use fractional distillation. This is how you do it.
1)You put your mixture in a flask and stick a fractionating column on the top. Then you should heat it.
2)The different liquids will all have somewhat different boiling points so they will evaporate at different temperatures.
3)The liquid with the lowest boiling point evaporates first, when the thermoemeter temperature matches the boiling point it will reach the top of the column.
4)Liquids with higher boiling might start to evaporate, however the column is cooler towards the top so they will condense on the way up.
5)When the first liquid has been collected, you raise the temperature until the next one gets to the top and you repeat the process.

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