If there is no particle of solute left undissolved in a solution, the solution is called homogeneous solution. From a homogeneous solution no solute is obtained on filtration. The entire solution passes through the filter paper.
From a homogeneous solution, soluble solute cannot be separated from the solvent by filtration. Solvent and solute can sometimes be separated by heating the solution.
When a pan containing salt solution is heated, the water of the solution evaporates and salt particles are left behind in the pan. In slow evaporation of the water from the solution, the left behind particles of the salt have geometrical shape. These are called the crystals of salt.
When the solution of a substance is placed in a vessel and is allowed to evaporate without heating, the crystals of the solute are obtained after a few days. This way we get the crystals of substances like common-salt, alum, sugar, etc.
When an insoluble substance is dropped in water, it settles down to the bottom of the vessel containing water. The settling down of the substance in the liquid is known as sedimentation. When an insoluble substance settles down to the bottom of the vessel, the clear liquid can be poured slowly into another vessel. This is known as decantation.