Separation techniques Flashcards
Name and define words to do with this unit
Any of
Pure, impure, solution, solute, soluble, insoluble, dissolves, residue, filtrate
refer to book for defintions
What is crystillisation?
Used to separate a solid from a liquid e.g salt from water. The solution/mixture is boiled until there is very little liquid, then it is left to evaporate fully
What is distillation?
This method is used to separate liquids with different boiling points (e.g ethanol and water) or liquids from dissolved substances (e.g water from saltwater)
What is fractional distillation
This is used to separate liquids with close boiling points (e.g ethanol and water), The glass beads in the fractionating column have a large surface area. So the liquids go through a process of vaporisation and condensation. The liquid with the lower boiling point will spend more time as a vapour and rise up the column faster.
What is thin layer chromatogrophy
Thin layer chromatography works similarly to paper chromatography except the stationary phase is a thin layer of silica gel of alumina powder on a plastic or glass plate and the mobile stage is a solvent of choice. It’s more accurate/sensitive than paper chromatography, faster, has a larger range of solvents/stationary phases and the results are easier to interpret. It’s often used for more delicate and complex substances.
What is paper chromatography
This is used to separate multiple substances in a single mixture like in ink. It relies on two stages: the stationary and mobile phase, in paper chromatography, the stationary phase is the paper and the mobile phase is the solvent (a liquid). A drop of the substance is put on the paper and the solvent will carry it up the paper. The substances with a greater affinity for the mobile phase will travel further
What is gas chromatography
In gas chromatography, the stationary phase is a column lined with silica gel of alumina powder and the mobile phase is the carrier gas (which is unreactive e.g nitrogen). The sample is turned into the gas state and injected into the column. This form of chromatography relies on an affinity for the stationary phase. Each substance in the sample will take different times to pass depending on how strongly they bond to the stationary phase. When a substance pass through the detector, a signal is sent to the computer where a chromatogram is recorded.
How can you tell if a substance is pure or unpure
- if the subsatance has a melting point over a range then it is unpure
- Through chromatography
What is filtration
This method is used to separate a liquid from a solid. The solid remains on the filter as residue, and the liquid that passes through is the filtrate
Which separation technique?
A student wants to find out the pigements in her pen
Chromatography
Which separation technique
Retriving water from a solution (the 2nd substance has a much lower boiling point)
Which separation techniques
Two substances with similar boiling points
Fractional distillation
Which separation technique
oh no! I’ve dropped all my expensive himilayan in a big bowl of water
Crystilliastion
