energy
Energy is the ability to cause changes in matter. For example, your body uses chemical energy when you lift your arm or take a step. In both cases, energy is used to move matteryou. Any matter that is moving has energy just because its moving. The energy of moving matter is called kinetic energy. Scientists think that the particles of all matter are in constant motion. In other words, the particles of matter have kinetic energy. The theory that all matter consists of constantly moving particles is called the kinetic theory of matter . You can learn more about the theory at this URL: http://www. youtube. com/watch?v=Agk7_D4-deY .