Physical separation techniques Flashcards
What are these techniques used to separate?
Mixtures
What is filtration used for?
- To separate an insoluble solid from a liquid
Filtration steps:
1) Pour the mixture into the filter paper which is positioned in the filter funnel above the flask
2) The liquid passes through the tiny pores in the filter paper
3) The solid cannot pass through the filter paper so is trapped and separated.
What is crystallisation used for?
- To separate a soluble solid from a liquid
What does aqueous mean?
Dissolved in water
Crystallisation steps:
1) Pour the solution into an evaporating dish and heat it
2) Stop heating when crystals form and allow it to cool down
3) Separate the left over liquid from the crystals
4) Dry the crystals
What is a solvent?
A liquid in which substances can dissolve
What is simple distillation used for?
To separate a dissolved solid from a liquid, while keeping the liquid
Simple distillation steps:
1) Place solution into flask
2) Evaporate the liquid by heating, turning it into a vapour.
3) Vapour rises up the glass tube
4) Vapour passes into the condenser which condenses the vapour back into a liquid
5) Collect the liquid in the beaker
Simple distillation apparatus:
- flask
- glass tube - surrounded by a condenser
- cold water running continuously through the condenser
- thermometer
What is fractional distillation used for?
- To separate a mixture of different liquids
Fractional distillation steps:
1) Pour the mixture into a flask
2) Gently heat, so the liquids will start to evaporate (the one with the lower boiling point will evaporate more easily)
3) When they reach the fractionating column, they will condense back into the flask
4) Evaporate again - repeated evaporating and condensing increases the amount of the lower boiling point chemical in the fractionating column
5) When the thermometer shows a constant temperature, we know the vapour is a pure substance, not mixture
6) Vapours pass into the condenser and turn back to a liquid
7) Collect liquid and then continue heating the leftover substance until the other liquid is collected
Fractional distillation apparatus:
- flask
- fractionating column
- thermometer
- condenser
- cold tap water
What is paper chromatography used for?
- To separate substances based on their different solubilities
Paper chromatography steps:
1) Draw a pencil line near the bottom of the chromatography paper
2) Put the dots of colours on the pencil line
3) Place the bottom of the paper in a solvent
4) The solvent makes its way up the paper and dissolves the ink in the coloured dots, carrying it up the paper
