1. Lead a discussion about matter. Begin by choosing a common object and breaking it down hypothetically into smaller and smaller components. For example: chair > wood > vascular cells > cellulose molecules > carbon atoms > protons, neutrons, and electrons. Describe matter as a collection of atoms and molecules. Describe elements as a collection of atoms of the same kind.

2. Show students the The Origin of the Elements video and discuss the following:

• Where did the matter that makes up Earth come from? (It formed in stars.)
• How do stars make carbon and other elements from hydrogen? (Great heat and pressure causes hydrogen atoms to fuse.)
• How do the elements formed in stars elements get scattered through space? (through star explosions)
• What do these new elements sometimes become? (new planets or part of new stars)

3. Lead a discussion about solid matter. Ask students:

• What does the term solid matter mean to you?
• What makes matter solid? If we could see the particles that make up matter, what would they look like?

4. Show students the Atoms: The Space Between video and discuss the following:

• How much of an atom is relatively solid? How much is empty space? (A good analogy is the comparison between a large courtyard and a small grain of sand.)
• What keeps you from falling through your chair? (electric fields)

5. Lead students through the following thought experiment: A pitch-dark room contains a tired helium balloon that is neutrally buoyant. You need to determine the location of that balloon. It could be anywhere in the room. You can detect the balloon only by poking it with a broomstick. Is it possible to determine the location of the balloon by poking it? (No, because each attempt to detect it causes its location to change.) Explain that this is analogous to Heisenberg's uncertainty principle, which states that the act of detecting an electron necessarily causes its location to change.

6. Watch the Quantum Mechanics video and discuss the following:

• Ernest Rutherford disproved the prevailing notion that the atom was a solid ball. How did he describe the structure of an atom? (as a small nucleus with electrons orbiting it like planets orbiting the sun)
• Rutherford realized that there was a problem with his idea. What was it? (Orbiting electrons would soon spiral into the nucleus, destroying all matter in a short time.)
• Niels Bohr provided a solution to Rutherford's problem by proposing a special restriction on the orbits of electrons. What was this restriction? (Electrons are restricted to specific energy levels; they can't exist outside of these energy levels.)
• Erwin Schrödinger added special equations to the Bohr-Heisenberg model that allowed physicsts to determine the probability of an electron occupying a particular energy level. What were these equations called? (wave equations)