Molecules have a certain size and mass; There is a certain interval between molecules; Molecules are constantly moving; There is a certain force between molecules; Molecules can make up matter, and in chemical changes, molecules can be divided into smaller particles: atoms. With the change of temperature, molecules can be transformed into each other in three States. The same molecule has the same properties, but different molecules have different properties. The smallest molecule is an isotope of hydrogen molecule, which is a hydrogen molecule without neutrons. A molecule with a mass of 1 has a relative molecular mass of several million. Molecules with relative molecular mass exceeding several thousand are called polymers.