The four states of matter in the Kinetic Theory of Matter are solid, liquid, gas and plasma. Solids are basically objects, such as a rocks and humans. They have a definite volume and shape. They cannot be compressed as the molecules in a solid are very closely packed due to strong intermolecular forces that bonds the molecules together. They expand when heated and contract when cooled. When heated, the molecules vibrate the more and more vigorously in their places when the temperature increases. Liquids are water-like matter, such as seawater and paint. They have a definite volume, however have no definite shape, as the intermolecular forces are not as strong as those in solids to bond the molecules together. Hence, the molecules will move around the container when tilted to reach a horizontal level (plane). They can be compressed, however only to a small extent. They expand when cooled (ice in solid state) and contract when heated (water vapour in gaseous state). The molecules will then become compacted or move further apart when in the respective states. The molecules will lose energy when steam condenses to water. Gas is basically the air. The air is usually made up different kinds of gases, such as oxygen and carbon dioxide. However, they all share common characterisics. Gases do not have a definite volume and shape, thus able to fill up anything, such as the atmosphere. They can be compressed as the intermolecular forces are weak. The gas molecules are spaced far apart, and they move in a continuous and random motion. Their speed varies according to the temperature and the number of atoms. The higher the temperature or the less the atoms, the faster they move. They bounce away from any other molecules (gas, dust or smoke), thus have no fixed motion. This is called the Brownian Motion. Diffusion is greatly present, where the molecules will diffuse in the air till it reaches a state of equilibrium. Gas also expands greatly when heated and contracts greatly when cooled.
Plasma is the superheated phase were electrons get torn from the atom (ionization). It is the rarest phase of matter on earth although it is the most common in the universe. They can be natural (lightning and the Sun) or man-made (fluorescent light tubes).