Matter is everything around you. Atoms and molecules are all composed of matter. Matter is anything that has mass and takes up space. (examples of things made from matter - a shoe, a lightbulb, a rock, the air you breath)
Particle - A particle is a tiny piece of matter
Substance - Made up from particles of matter.
States of matter - The three most common states of matter on Earth are liquids, solids, gases (there are also Bose Einstein Condensates which are found at extremely low temperatures, and Plasmas)
Common Phase changes Melting - Change of state from a solid to a liquid. Evaporation - Change of state from a liquid to a gas. Condensation - Change of state from a gas to a liquid. Freezing - Change of state from a liquid to a solid.
Irreversible - When something cannot be undone
Reversible - When something can be made to return to its original state.
Reaction - Reactions occur when two or more molecules interact and the molecules change.