When would a gas be described as a vapor?

Answer 1

You might hear the term vapor. Vapor and gas mean the same thing. The word vapor is used to describe gases that are usually found as liquids. Good examples are water or Mercury (Hg). Compounds like carbon dioxide are usually gases at room temperature so scientists will rarely talk about carbon dioxide vapor. Water and mercury are liquids at room temperature so they get the vapor title.

Answer 2

A gas is described as a vapor when it is in the gaseous state at a temperature below its critical temperature. Vapor is often used to refer to gases that are close to condensing into a liquid or solid form.