The copper sulfate compound (CuSO4) is a salt and it is used to illustrate the inorganic chemical reaction called mineral hydration.
The pentahydrate copper sulfate usually has a blue color.
When pentahydrate copper sulfate is heated, to prove the exothermic reaction, the water inside evaporates, leaving behind a new anhydrous form whose color is white.
If water is added to the new anhydrous form, it will become the original blue pentahydrate copper sulfate.
Do you mean it as Copper metal metal? If yes, the metal copper is first converted to blue coloured copper sulphate by the reaction with concentrated sulphuric acid.
Cu + H2SO4 -----> CuSO4 (aq) (Blue)
the solution on evapourasion gives the Blue crystals of CuSO4*5H2O which on further heating gives anhydrous CuSO4 which is colourless.
CuSO4*5H2O Blue --Heating--> CuSO4 white + 5H2O
Other method is the blue coppersulphate solution will react with ammonium thiocyanate (NH4CNS) salt solution to give the white (colourless) precipitate of copper thiocyanate Cu(CNS)2.
hydrogen sulphide because its not stable and gets oxidized in air........!