|Step 1. Rock salt is crushed into little pieces and added to water. The salt dissolves in the water but the earthy impurities are insoluble. |
Step 2. The solid sandy bits are separated from the salt solution using filtration. The mixture is passed through some filter paper held in a funnel. The salt solution can pass through the small holes in the filter paper because all the particles are tiny. The earthy impurities cant pass through the holes, because the particles are too big.
Step 3. The salt solution is changed to salt by evaporating the water. The solution is heated so that the water evaporates, leaving the salt behind.
Filtration is often used to separate the solid and liquid parts of a suspension. The liquid part is called the filtrate. The solid that remains on the filter paper is called the residue.