1. All matter is made up of tiny particles: This is the fundamental idea - everything, from a rock to air, is composed of tiny particles called atoms or molecules.
2. The particles are constantly moving: The particles are in constant random motion, with the amount of movement increasing with temperature.
3. There are spaces between the particles: These spaces are larger in gases, smaller in liquids, and very small in solids. This explains the compressibility of gases and the ability of liquids and solids to mix.
4. Particles attract each other: The strength of the attraction varies between different substances, explaining the different properties of solids, liquids, and gases.
There is no fifth principle in the standard particle theory.
