Depending upon the physical states of the solute and the solvent, the solutions can be classified into the following types:

Out of these nine types of solutions, three solutions, namely solid in liquid, liquid in liquid, and gas in liquid are very common. In all these three types of solutions, liquid acts as a solvent.

The solutions in which water is the solvent are called aqueous solutions while those in which the solvent is other than water are called non-aqueous solutions. The common non-aqueous solvents are ether, benzene, carbon tetrachloride, etc.

What is the observation on adding a solute crystal to a supersaturated solution?

The solute precipitates out of the solution

The answer is 4. The solute precipitates out of the solution.

A supersaturated solution is a solution that contains more solute than it can normally dissolve at a given temperature. When a solute crystal is added to a supersaturated solution, the solute will precipitate out of the solution. This is because the presence of the solute crystal provides a nucleation site for the solute to crystallize.

The other options are not correct. A colloidal solution is a solution that contains particles that are dispersed in a solvent, but the particles are too small to be seen with the naked eye. The solute will not dissolve in the solution because the solution is already saturated. The solution will not desaturate because the solute crystal provides a nucleation site for the solute to crystallize.

Therefore, the observation on adding a solute crystal to a supersaturated solution is that the solute precipitates out of the solution.