According to the Royal Society of Chemistry, copper sulfate becomes dehydrated and changes physical properties when it is heated. The color as well as the makeup of the element changes when heat is applied.
Copper sulfate is generally a blue color. It is sometimes called blue copper for this reason. When the copper sulfate is heated up, it quickly turns to a pure white color that has no hint of blue in it. Water also comes out of the copper sulfate and is able to function as any other type of water would typically function.
When the copper sulfate becomes hot, it begins to become dehydrated. This also changes the makeup of the element and it can become less solid and in more of a powder form than it was before. Since it is a dehydrated substance, it does not have much water in it that can hold it together in a solid shape or form.
Copper sulfate that has been dehydrated has the possibility to rehydrate. The water that came out of the copper sulfate when it was dehydrated can be added back to the material and the copper sulfate will be able to return to its original form. Water from other sources can also be added to the copper sulfate to help it become blue and solid again.