Key Idea: All matter is made up of atoms.

Students are expected to know that:

  1. Matter is anything that has mass and takes up space.
  2. Matter includes all gases, liquids, and solids, which make up all living and non-living things.
  3. Light and heat are not matter.
  4. All matter—solids, liquids, and gases—is made up of discrete particles (atoms), rather than being continuous, and that these atoms are the matter rather than contained in matter. In other words, the atoms are not floating or embedded in some other substance, such as air or a liquid.
  5. Matter can exist even when it cannot be seen. For example, gases or vapors are matter even though some of them cannot be seen.
  6. Anything made up of atoms is matter.
  7. It is because atoms take up space and have mass that all matter takes up space and has mass.


  1. It is not expected that students will know about the internal structure of atoms or the existence of subatomic particles and, therefore, that these subatomic particles have mass.