Vapor pressure

Vapor pressure is the pressure of a gas in a container. It's like when you blow up a balloon: the air inside the balloon is pushing against the sides of the balloon, and this push is the pressure of the gas inside the balloon. Vapor pressure is the same thing, but with a gas in a container instead of inside a balloon. Think of the container like a big balloon: the gas inside the container is pushing against the sides of it, and this push creates pressure. The pressure of the gas is called its vapor pressure.