Question

Why do copper vessels turn green with passage of time

Answer 1

Because as time passes it started corroded or reacting with H2O AND CO2 And thus turn greed due to corrosion

Answer 2

Copper turns green because of chemical reactions with the elements. Just as iron that is left unprotected in open air will corrode and form a flaky orange-red outer layer, copper that is exposed to the elements undergoes a series of chemical reactions that give the shiny metal a pale green outer layer called a patina.

2Cu + H2O + CO2 + O2 →CuCO3 + Cu(OH)2