(i)What is it used for:
This is used to separate a liquid from a solution of a solid. The solid is called the solute and the liquid is called the solvent.
(ii)What happens:
The solution is heated in a round-bottomed flask. The solution boils. The solvent evaporates into vapour and rises. It is then cooled when passed through a condenser, which changes back to liquid, called the distillate.
(iii)How it works:
The solvent has a low boiling point and so is easily changed into a gas on heating. The solute has a high melting and boiling point and so does not boil and remains in the flask.
(iv)Experiment: Obtaining pure water from sea water
Heat the sea water in a round-bottomed flask. As the solution boils, water evaporates and become water vapour. The vapour rises and enters the condenser. It is cooled there and condenses into a liquid, and drips out of the other end into a beaker.
Result: Pure water is obtained as a distillate.
(v)Notes:
-The thermometer shows a constant temperature during the distillation as pure solvent is being distilled. Thus, this temperature = boiling point of solvent
-A thermometer is not essential in the apparatus. A cork can be used instead.
(vi)Apparatus needed:
Bunsen burner, round-bottomed flask, thermometer (optional), stoppers, condenser, beaker
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