What would happen if you could tear a very small piece of a substance in half, then keep on tearing it in half? Could you tear it in half forever? Or would you finally come to one last piece too tiny for you to tear in half?

If you could keep tearing a piece of copper in half until you got to the tiniest piece possible, and if you could still see it, you would find that this last piece would still be copper and would have the physical characteristics of copper.

If you could tear a piece of iron the same way, the last piece would still be iron.

Scientists call the very smallest piece of a substance an "atom." Atoms are so small, they can't even be seen by the naked eye.

[Is a "naked eye" an eye with no clothes on? Probably, it means a person's eyes without the help of a magnifying glass or microscope.]

The smallest piece of copper is a copper atom.

The smallest piece of iron is an iron atom.