Mixtures can be easily separated into pure substances. This process is called purification. It is done by using physical methords without chemical reactions. There are several methods of purification but in this post, filtration would be the one we would be talking about.
Filtration is used to separate an insoluble solid from a liquid. A simple way of doing this is in shown in this figure.
The mixture is poured through a filter which is usually made of paper. The filter paper has tiny holes which the particles of the liquid are able to pass through. The particles of the solid are large. They cannot pass through the holes and are trapped by the filter paper. The holes allow water and dissolved substances to pass through, but not the large insoluble particles.
The solid collected in the filter paper is called the residue. The liquid passing through the filter paper is called the filtrate.
Filtration is used to purify drinking water by removing insoluble solids. Small filter systems are used in the home to filter tap water. At water purification plants, large filters are used to remove sand and mud from the water. The filters at these plants do not use filter paper, but consist of layers of sand, gravel and pebbles.
2.2: Words used
Soluble: A substance that will dissolve.
Insoluble: A subsance that will not dissolve
Solute: Normally a solid which dissolves
Solvent: Normally a liquid which does the dissolving
Solution: Solute + Solvent
Residue: Insoluble solid which is trapped in filter funnel
Filtrate: A solution that passes through the filter funnel.
Crystal: A solid that reappears from the solution.