# Why is anhydrous copper sulfate a white powder, while CuSO_4*5H_2O a blue crystal?

$\text{Copper sulfate pentahydrate}$, $C u S {O}_{4} \cdot 5 {H}_{2} O$, gives beautiful macroscopic crystals.....
The water molecules are actually incorporated into the coordination sphere of the copper ion. Dry the crystals thoroughly (no easy task), and you are left with anhydrous $C u S {O}_{4}$, a white salt.