gas

Gas is the invisible stuff that is all around us in the air. Gas is made up of tiny particles called molecules, which can move around and bounce off each other. Most of the air we breathe is a kind of gas called nitrogen. Another type of gas found in the air is called oxygen, which helps us to breathe. Gas can also be in liquid form, like gasoline and propane, which can be used for energy. In its solid form, gas has a different name: it's called a gas.