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Topic 2b - Separation techniques - Coggle Diagram
Topic 2b - Separation techniques
Simple distillation
Used when dissolved solute has a much higher boiling point than the solvent
Method
4) The component with the higher boiling point is left in the flask
3) As the vapor rises, it passes into the condenser, where it is cooled by the water that runs between the two tubes but doesn't mix with the substance, and condenses back into liquid state, where it is collected in a container
2) Heat the distillation tube, and the component with the lowest boiling point will evaporate
1) Pour the sample into a distillation flask, that is connected to a cold tap, run water through it, to keep it cool
Used to separate out a solvent from a solution, in industry its used to get pure water from sea water
Fractional distillation
Used to separate a liquid from a mixture of miscible liquids (liquids that completely mix with each other)
Used to separate crude oil
Method
1) The different liquids will have different boiling points, so will evaporate at different temperatures
2)The liquid with the lowest boiling point will evapourate and reach the top of the column first.
3) Liquids with higher boiling points will also start to evaporate, but the column is cooler at the top, so they will only rise part of the way up before condensing and running back down due to the temperature gradient, hottest at the bottom, coldest at the top
4) When the vapour reaches the top, it passes into the condenser where it can be collected
The solution becomes more concentrated during simple distillation because the solute stays behind
Filtration
Used to separate and insoluble solid from a liquid
Method
1) Fold a piece of filter paper into a cone, and place it into a funnel which is sitting in the neck of a conical flask
2) Pour the mixture containing the insoluble solid into the funnel, the pores in the paper are large enough to let water molecules through by small enough to stop insoluble solid particles
3) The solid will be left behind in the funnel
4)Rinse with distilled water and leave to dry
Used to purify a liquid by removing solid impurities
Crystallisation
Used to separate a soluble solid and a solution
Method
1) Place and evaporating dish on top of a hot water bath on a tripod with a gauze mat, we use this because it gives more control over heating than using a Bunsen burner flame directly on the evapourating basin
2) Place a Bunsen burner underneath
3) Pour the solution into the dish and gently heat it
4) Once some of the water has evaporated, or when you see crystals starting to form, remove the dish from the heat and leave to cool
5) You should be left with pure crystals
If a solid can be dissolved it is soluble
The solution is heated to remove enough solvent to produce a saturated solution, one that cannot hold any more solute
Paper Chromatography
Used to separate a mixture of soluble substances and identify them
Phases
Mobile phase: always a liquid or gas, where the molecules can move,
Stationary phase: always a solid, where the molecules cannot move
In paper Chromatography, the paper is the stationery phase, and the water is the mobile
Method
1) Draw a line near the bottom of a sheet of paper with pencil
2) Spot the ink by placing a small amount on the line, when placing the paper in the container, make sure the solvent isn't touching the ink
3) Wrap the paper around a pencil so it is held in place, the solvent will begin to move up the paper
4) Different inks will move up the paper at different rates, so they will separate out, if any of the inks are insoluble, then they wont go up the paper
5) Once the water has almost reached the top of the paper, take the paper out from the beaker and leave to dry
6) Mark the point the solvent has reached
Results
The results are known as a chromatogram
The ratio between the distance traveled by the dissolved substance and the distance traveled by the solvent
Known as Rf value
Rf vale = distance traveled by solute/ distance travelled by solvent
Pure substaces
Mixture
Constists of 2 or more elements or compounds not chemically combined together
Chemical properties of each substance in the mixture are unchanged
Pure
Single element or compund, not mixed with any other substances
Melt and boil at a specific point