Why copper(II) pentahydrate change in color when these elements hydrate compouds are heated?

Answer 1

If I understand your question correctly you are asking why the colour of compounds like CuSO4.5H2O changes upon heating.

In this compound the water molecules are co-ordinated by the Cu(II) ion, forming a complex ion. Because of the interaction of the water molecules with Cu+2, the energy levels which can be occupied by electrons of Cu+2 take a certain value. The colour of the compound reflects the difference in the energy levels between the ground and excited states.

When you heat the compound, water evaporates, the complex ion is destroyed, thus the energy levels change, resulting in a change in colour.

Answer 2

when copper is heated at 5 degree intervals it does change color. just the addition of heat to the metal or a compound containing copper will undergo a chemical change but not a physical.