Question

Why do copper granules become black after heating?

Answer 1

Short Answer-

Copper granules are reduced to copper oxide, which is black in color. Hence, copper granules become black on heating.

Answer 2

The copper granules become black after heating because the hot metal of the copper forms a reaction with the oxygen (O2) in the air and in turn forms a black copper oxide. The copper oxide is black in colour; hence, it turns black.

The proper equation to signify the explanation is: 2 Cu (s) + O2 (g) ---> 2 CuO (s).