Given a solution of substance A, how will you test whether it is saturated or unsaturated with respect to A at the prevailing temperature? What is observed when a hot saturated solution of a substance is allowed to cool?
To given solution add a small amount of substance A to its given solution. If A dissolves and clear solution is formed, then it is an unsaturated solution of substance A. If the substance A added does not dissovle and settles down, then the solution is saturated.
When a hot saturated solution of a substance is allowed to cool, some of the salt reappears.