Question

Are all the hydrated salts crystalline? What are anhydrous salts?

Answer 1

Hydrated salts have water within their crystals when the crystals are formed from water; an anhydrous salt is where the crystal has had the water driven out.

An example is the cupric ion, reasonably shown with copper sulphate. Water bonds to it and the ion goes blue. Ammonia leads to a more intense blue. The hydrated ions form the crystal, on heating, the crystal powders and the material goes white.