Year 7 REVISION – Particle Theory Brownian Motion: the random movement of microscopic particles in a fluid, as other particles randomly bump them. Solids, liquids and gases are all made up of PARTICLES. In a solid PARTICLES are held very CLOSE together to form a REGULAR pattern, where they can only VIBRATE. In liquids they are CLOSE together, but they can SLIDE past each other and they have no REGULAR pattern. In gases, PARTICLES Are free to MOVE in all DIRECTIONS at a very high speed. States of Matter KEYWORDS Particle A tiny portion of a substance Volume The amount of space taken up by a substance Density Heaviness for its size Compress Making a volume smaller by increasing the pressure Diffusion Random mixing of particles Vibration Movement of a particle around a fixed position. Gas pressure The force of collisions of particles from a gas on a container. Melting point The exact temperature at which a substance melts Boiling point The exact temperature at which a substance boils Evaporation When a substance turns from a liquid to a gas Condensation When a gas cools and turns into a liquid 1 2 3 4 Solid to liquid= MELTING Liquid to gas= EVAPORATION Liquid to solid= FREEZING Gas to liquid= CONDENSATION Extension:Some substances can turn from a solid to a gas. This is called SUBLIMATION. An example of this substance is dry ice.