An explanation of how the mass of atoms varies depending upon the element. Gold and silver rings are shown and an explanation of why the gold ring is heavier is given. The fact that gases also have mass is described. This is explained by stating that an opened bottle of lemonade is lighter than an unopened one. The mass of Helium being lighter than air is also mentioned.

First broadcast:
25 March 2003

Use the clip as an introduction to explain the concept of atomic mass. Relate this to the three subatomic particles and their masses, allowing students to link the properties of the three particles to mass number. The class could carry out simple card sorts for elements where they are given some of the properties, including atomic mass, and have to arrange elements into order.