Why does copper turn green?
Show answer & explanation
Answer: It forms copper carbonate
It grows mold — Wrong. The green color is not from mold or any biological growth. It's a chemical compound formed through reactions with the environment. This green layer is called patina and is actually protective.
It forms copper carbonate ✓ — Correct! Copper reacts with oxygen, water, and carbon dioxide in the air over time. This creates a green layer of copper carbonate (CuCO3) and copper hydroxide. This is why the Statue of Liberty is green - it's made of copper! The patina actually protects the metal underneath from further corrosion.
Paint oxidizes on it — Wrong. There's no paint involved. The green color comes from chemical reactions of the copper itself with environmental factors. Pure copper starts out reddish-brown and naturally develops the green patina over years.