1Simple distillation
Distillation separates a liquid from a solution. The water boils off, the vapour cools in the condenser, and pure water drips out.
distillationcondenser
Lesson 8.4 notes
Distillation and chromatography
Getting a pure liquid back from a solution, and separating the dyes in an ink.
2Boiling, then condensing
Distillation uses two changes of state: the liquid boils in the flask, then the vapour condenses back into a liquid.
boilingcondensing
3Drinking water from sea water
Distillation can turn sea water into drinking water. The water evaporates and condenses; the salt stays behind.
desalination
4Paper chromatography
In chromatography, a solvent moves up the paper and carries the dyes with it. Each dye moves a different distance.
chromatographysolvent
5Setting it up
Draw the start line in pencil, and keep it above the solvent, or the dyes dissolve into the solvent instead of moving up.
start line
6Reading a chromatogram
Spots at the same height on the same paper are the same dye. Ink X contains dyes A and B.
chromatogram
7Testing for purity
A pure substance gives just one spot. A mixture of dyes gives two or more.
pure substance
Explore: Chromatography lab
Pick an ink and a solvent, then run the chromatogram.
Common mistake: Distillation is not just evaporation
In evaporation the water escapes into the air and you keep the solid. In distillation the vapour is cooled and condensed, so you collect the pure liquid as well.
Remember
- Distillation: boil the liquid, then condense the vapour to collect a pure liquid.
- Chromatography separates dyes: each one moves a different distance up the paper.
- A pure substance gives one spot. Draw the start line in pencil, above the solvent.