Separation Techniques Flashcards
What do separation techniques work for?
Mixtures
What are the 5 physical separation techniques
Filtration Crystallisation Simple distillation Fractional distillation Chromatography
How does chromatography work
1) Draw a line in pencil near the bottom of some filter paper
2) add a spot of ink onto the drawn line and place the paper into some solvent e.g water, ethanol (solvent depends on the whether the compounds dissolve in it
3) make sure the ink isn’t touching the solvent
4) place a lid on top so the solvent does not evaporate
5) the solvent seeps up the paper, carrying the ink with it
6) each different dye in the ink will move up the paper at different rates, and will separate out
7) if any of the dyes are insoluble(wont dissolve) then they stay on the drawn line
8) when the solvent has almost reached the top, take out the paper and dry
9) the end pattern is called a chromatogram
(The point the solvent reaches is called the solvent front)
What does filtration separate
Insoluble solids from liquids
How does filtration work?
Filter paper is place in a cone shape in a funnel
The liquid is poured in - the liquid goes through and the solid doesn’t
How does evaporation work
The solution is poured into an evaporating dish
The solution is heated, and the solvent will evaporate whilst the the solution will get more concentrated
Heat until only crystals are left
How does crystallisation work
Same first stages as evaporation
(Place solution in evaporating dish and heat)
But when some of the solvent has evaporated or some crystals appear remove the dish from heat and leave to cool
The salt should form crystals as it becomes insoluble in the cold, highly concentrated solution
Filter the crystals out and leave to dry in a warm place
When is crystallisation used and not evaporation
If the salt decomposes when it is heated
(The source of heat is removed in crystallisation and left to cool
What are the two ways of separating soluble solids from solutions
Evaporation
Crystallisation
When is fractional distillation used over simple distillation
When there is a mixture of liquids or if the liquids have similar boiling points
How does simple distillation work
The solution is heated in a flask.
The part of the solution with the lowest boiling point evaporates first
The vapour is cooled, and condenses in a CONDENSER and is collected in a beaker at the bottom
The rest of the solution is left behind in the flask
Can be used to get pure water from seawater
How does fractional distillation work?
*used for separating a mixture of liquids
Place the mixture in a flask and place a FRACTIONATING COLUMN on top (with a thermometer which only measures the top of the fractionating column)
The different liquids will all have different boiling temperatures, so will evaporate at different times
The liquid with the lowest boiling point will evaporate first. When the temperature on the thermometer matches the boiling point, the liquid will be at the top of the column, will condense and fall down into a beaker
Other parts of the solution may start to evaporate and rise, but will not reach the top as it is too cool for them up there
Once the lowest one has been collected, up the heat to evaporate the next one
