Most matter^* on Earth exists in one of three phases: solid, liquid, gas.

Matter is made up of tiny invisible^* particles that move. The space between the particles and the speed at which they move (their energy^*) determines the matter's phase. Solid particles are close together and move slowly. Liquid particles are farther apart and have more energy than solid particles. Gas particles are very far apart and move very fast.
Matter can change from one phase to another. Gases can become liquids if the particles are cooled (slowed down) or squeezed together under high pressure^*. Many gases are transported and stored as liquids because liquids take up less space than gases. (28.8K) (56.7K) (download)