Plaster of Paris should be stored in a moisture-proof container. Explain why?

Explanation

Plaster of Paris (POP) should be stored in a moisture-proof container because Plaster of Paris, a powdery mass, absorbs water (moisture) to form a hard solid known as gypsum.
`underset((POP))CaSO_(4)
.(1)/(2)H_(2)O+1(1)/(2)H_(2)O to underset("gypsum"("Hard solid"))CaSO_(4).2H_(2)O`