Question

A metal when left in air for many days it turns green but when heated in air turns black thos metal is

Answer 1

iron rron because they turn black in heating

Answer 2

Answer:

A metal when left in air for many days it turns green but when heated in air turns black that metal is copper.

Explanation:

Copper reacts with moist CO2 in the air to form green colored CaCO3 called as patina.  The corrosion of copper due to reaction with oxygen and carbon dioxide for green color copper carbonate.

2Cu + O2 -> 2CuO  

CuO + CO2 -> CuCO3

Many copper statues are turned green due to corrosion of copper in form of copper carbonate. Rain water reacts with carbon dioxide form acid rain containing carbonic acid (H2CO3).

Acid rain water reacts with copper statues to turn them green.  

Cu + H2CO3 -> CuCO3 + H2  

Heating of copper undergoes oxidation of copper with oxygen to turn it black due to formation of layer of copper oxide.