You might have noticed that when copper powder is heated in a china dish, the surface of copper powder becomes coated with black colour substance.(i) How has this black-coloured substance formed?(ii) What is that black substance?(iii) Write the chemical equation of the reaction that takes place.

Yes, the formation of a black-colored substance on the surface of copper powder when heated in a china dish is a common observation. This phenomenon is known as the "oxidation of copper."

(i) Formation of the black-colored substance:
The black-colored substance is formed due to the oxidation of copper. When copper is heated in the presence of air, it reacts with oxygen to form copper oxide. This reaction is an example of a redox reaction, where copper loses electrons to oxygen.

(ii) Identity of the black substance:
The black substance formed on the surface of copper is called "copper oxide." There are two common forms of copper oxide: cupric oxide (CuO) and cuprous oxide (Cu2O). The specific form formed during the oxidation depends on the reaction conditions, but both are black in color.

(iii) Chemical equation of the reaction:
The reaction between copper and oxygen to form copper oxide can be represented by the following chemical equation:

2Cu(s) + O2(g) -> 2CuO(s)

In this equation:

Cu represents copper (in solid form).
O2 represents oxygen gas from the air.
CuO represents copper oxide, which is the black-colored substance formed on the surface of copper powder.