States of Matter

All matter is composed of very small, discrete particles, either atoms, ions, or molecules. The nature of a particular substance depends on the type and arrangement of the atoms within the molecule.

It is possible for these particles to assume different arrangements in space. For example, they can be arranged close together or far apart. They can be neat and orderly or random and disordered. Since two particles cannot occupy the same place at the same time, they can be pushed closer together only if there is empty space between particles. Sometimes they slip and slide past each other and sometimes they are locked rigidly into a specific position. The state in which any particular piece of matter exists depends on these properties. Under the right conditions, any substance can exist in all of the states of matter: solid, liquid, gas, or plasma.

The atoms, molecules, and ions that make up all matter are in constant motion, which can range from vibrating within a fairly rigid position to moving randomly at very high speeds. Movement is always in a straight line until some other force interferes with the motion. Like billiard balls, the moving particles can hit other particles or objects such as the walls of their container. These collisions cause the particles to change direction and, although no energy is lost, it can be transferred to other particles.

Various forces exist between the particles of matter. The degree of attraction or repulsion depends on such factors as whether the particles are electrically neutral or carry a charge, whether the charges are localized or balanced out, how big or small the particles are, and how far apart the particles are from each other.