When a mixture of dissolved solid potassium nitrate in water cools down why..

Question

does the potassium nitrate crystallise ?

Answer 1

Because hot water can dissolve more of it. In hot water the molecules of water are further apart from each other leaving room for the KNO3 molecules. When it cools the "room" shrinks and some olecules are kicked out of the room- and so crystallize or become solid.