Question

brown coloured copper powder on heating in air turn into black colour substance.​

Answer 1

This is because ,

air contains oxygen and copper is a reactive metal which reacts with oxygen to form the respective oxide.

=> 2Cu+ O2 ----> 2CuO

Answer 2

Explanation:

copper combines with oxygen to form copper oxide. here oxygen is gained and the process is called oxidation .on heating copper it reacts with oxygen present in atmosphere to form copper oxide.

Cu+O2 on heating 2 CuO