Filtration and Evaporation
Rock salt is a mixture of salt and sand.
Salt and sand are both compounds but because the salt is soluble in water and the sand isn't, the two can be separated using the following methods:
Simple distillation is used to separate a mixture of a liquid and a solid, for example ink.
(1) The liquid is heated and boils off.
(2) The vapour is cooled by cold water, condensed and collected leaving the solid behind.
This can be used to purify sea water or tap water.