Students are introduced to the idea that matter is composed of atoms and molecules that are ... molecules as they experiment with and observe the heating and cooling of a solid, liquid, and gas.

Substances can exist in three states of matter - solid, liquid and gas. All substances are made from particles, and the forces between the particles are different in solids, liquids and gases.

Matter is the "stuff ... Most substances can exist as a solid, liquid or gas. They can change state, usually when they are heated or cooled. For example, liquid water turns into water vapour ...