When a solute has been added to a solvent in such as amount that no more solute can dissolve in the solvent, the solution is said to be saturated. The concentration of the solution at this point is called its solubility. If any less than this amount is added, the solution is unsaturated. If more than this amount is added, the solution is supersaturated. Since a supersaturated solution by definition contains more solute than can be dissolved, a precipitate forms in the solution. Once a solution is saturated, individual molecules of the solute are constantly precipitating and dissolving again. However, no change in the actual solution occurs; for every molecule that precipitates, another molecule dissolves. A saturated solution is therefore a dynamic equilibrium where the precipitation of molecules and dissolution of molecules occur at the same rate. In other words, at any given moment, the amount of the precipitated solute is the same. Likewise, the amount of the dissolved solute is constant. For example, the equation representing the dissolving of table salt in water would be represented by the following equation.
