Thus the concentration of a substance [ (amount in moles)/(volume) ], pure solids and pure liquids have definite a constant concentration, for a given volume, whereas gases have a variable concentration. read more
Pure solids and liquids are not dissolved, therefore concentration is a concept that you can not apply to them. 2 Another way. If you consider only the molecules of solvent or gas surrounding these phases to calculate a concentration you come to the conclusion that this concentration is constant in a practical way. read more