Question

Why copper turns green and silver turns black when exposed to air?

Answer 1

The reason for this process is oxidation.

In air oxygen presents and it oxidise copper and silver.
Due to oxidation copper form a thin layer of green coating and silver.

Answer 2

Answer:

Copper vessels turn green when exposed to air for a long period of time due to corrosion. The copper reacts with the moisture and the various gases present in the atmosphere to form a mixture of copper carbonate (CuCO3) and copper hydroxide (Cu(OH)2) . The reaction is as follows:

2Cu + H2O + CO2 + O2 = CuCO3 + Cu(OH)2

This corrosion can be prevented by applying a layer of grease or paint cover that will prevent the copper surface from coming in contact with the air.

Explanation: