Incorporate fun, interactive activities to teach younger kids about the states of matter. Begin with what matter is before breaking the subject material down into the three major states: solids, liquids and gases.
Start out a discussion on matter by talking about what things are made up of atoms. Atoms make up everything: people, air, water and even buildings. Incorporate movement into a lesson plan to teach kids that atoms and molecules are always moving. Solids are atoms that are packed tightly together, so they move very little. They maintain the same shape at room temperature. Liquids are not packed as tightly together and take on the shape of the container that holds them. Gases are made up of atoms that are always moving; they never stay still. Kids can create the different states of matter in groups by moving slower or faster, closer together or further apart.
Another simple way to teach students about the states of matter is with a piece of ice. The ice begins as a solid. As it melts, kids see the ice become water, or a liquid. Finally, boil the water to show them how the matter turns into a gas. This also teaches students about phase change, which is the term used when matter moves from one state to another.