Here's why:

* Copper is a relatively unreactive metal. It sits below hydrogen in the reactivity series, meaning it's less reactive than hydrogen.

* Water is a weak oxidizing agent. This means it's not strong enough to oxidize (remove electrons from) copper atoms.

However, copper can react with:

* Hot water: When heated, water becomes more reactive and can react with copper, especially in the presence of oxygen, forming copper oxide.

* Acidic water: Acids can react with copper, releasing hydrogen gas and forming copper salts.

* Dissolved oxygen: Oxygen dissolved in water can react with copper to form copper oxide, causing a green patina on the copper surface.

So, while copper doesn't react with cold water on its own, it can react under specific conditions like high temperatures or the presence of acidic solutions.