What is observed when anhydrous copper(II) sulfate is mixed with water?

When anhydrous copper(II) sulfate is mixed with water, it undergoes a hydration reaction. The anhydrous form of this compound is white in color, but when it is added to water, it absorbs water molecules and transforms into hydrated copper(II) sulfate, which is known as copper(II) sulfate pentahydrate. This hydrated form is blue in appearance.

This change in color is a characteristic property of copper(II) sulfate, where the white anhydrous salt becomes a vibrant blue as it hydrates. This process is often used in experiments to demonstrate hydration and is also a fundamental concept in understanding how certain salts can change their physical appearance based on their water content. The other responses do not accurately describe this reaction, as pink is not a color associated with copper(II) sulfate and evaporation does not occur in this scenario, while it does not remain white after the reaction.