Chemistry GCSE: Separation Techniques

Crystallisation

1. Pour the solution into an ==evaporating dish== and gently heat the solution. Some of the ==solvent== will evaporate and the solution will get more ==concentrated==.
2. Once some of the solvent has evaporated, ==or== when you see crystals start to form (the ==point of crystallisation==), remove the dish from the heat and leave the solution to cool
3. The salt should start to form ==crystals== as it becomes ==insoluble== in the cold, highly concentrated solution
4. ==Filter== the crystals out of the solution, and leave them in a warm place to ==dry.== You could also use a drying ==oven== or a ==desiccator==.

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 all you have left are ==dry crystals==.

Filtration

1. ==Grind== the mixture to make sure the salt crystals are small, so will dissolve easily.
2. Put the mixture in water and stir. The ==salt== will ==dissolve==, but the ==sand won't==.
3. ==Filter== the mixture. The grains of ==sand== won't fit through the tiny holes in the filter ==paper==, so they collect on the ==paper== instead. The ==salt== passes ==through== the filter paper as it's part of the solution.

==Evaporate== the water from the salt so that it form ==dry crystals.==

Paper Chromatography

1. Draw a ==line== near the bottom of a sheet of ==filter paper==. (use a pencil to do this ~ pencil marks are insoluble and won't dissolve in the solvent)
2. Add a ==spot== of the ink to the line and place the sheet in a beaker of ==solvent==, e.g water.
3. The ==solvent== used depends on what's being tested. Some compounds ==dissolve== well in ==water==, but sometimes other solvents, like ethanol, are needed.
4. Make sure the ink isn't touching the solvent - you don't want it to ==dissolve== into it.
5. Place a ==lid== on top of the container to stop the solvent ==evaporating==
6. The solvent ==seeps== up the paper, carrying the ink with it.
7. Each different ==dye== in the ink will move up the paper at a different ==rate== so the dyes will ==separate out==. Each dye will form a ==spot== in a different place - 1 spot per dye in the ink.
8. If any of the dyes in the ink are ==insoluble== (won't dissolve) solvent you've used, they'll stay on the ==baseline==.
9. When the ==solvent== has nearly reached the ==top== of the paper, take the paper out of the beaker and leave it to ==dry==.

The end result is a pattern of the spots called a ==chromatogram==.

Distillation

1. ==Simple distillation== is used for separating out a ==liquid== from a ==solution.==
2. The solution is ==heated==. The part of the solution that has the lowest boiling point ==evaporates== first.
3. The ==vapour== is then ==cooled, condenses== (turns back into a liquid) and is ==collected.==
4. The rest of the ==solution== is left behind in the flask.
5. You can use simple distillation to get ==pure water== from ==seawater==. The ==water== evaporates and is condensed and collected. Eventually you'll end up with just the ==salt== left in the flask.
6. The ==problem== with simple distillation is that you can only use it to separate things with ==very different== boiling points - if the temperature goes higher than the boiling point, they will mix again.
7. If you have a ==mixture of liquids== with ==similar boiling points== you need Pure distilled water another method to separate them

Fractional Distillation

1. If you've got a ==mixture of liquids== you can separate it using ==fractional distillation.==
2. You put your ==mixture== in a flask ==fractionating column== on top. Then you heat it
3. The ==different liquids== will all have ==different boiling points== - so they will evaporate at ==different temperatures==.
4. The liquid with the ==lowest boiling point== evaporates first. When the temperature on the thermomet matches the boiling point of this liquid, it will reach the ==top== of the column.
5. Liquids with ==higher boiling points== might also start to evaporate. But the column is ==cooler== towards the ==top==. So they will only get part of the way up before ==condensing== and running back down towards the flask
6. When the first liquid has been collected, you ==raise the temperature== until the ==next one== reaches the top.

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