A bar of soap in the microwave grows to tremendous proportions.
Little Shop of Physics
A light bulb has the glass carefully removed, leaving the glass base and filament intact. The bulb is connected to AC electricity, and the filament quickly and dramatically burns out. This leaves the two wires that originally supported the filament separated by the glass in the base. Take a propane torch and heat the glass base (the bulb remnants are still connected to the electricity), a point is reached where the heated glass is no longer isolating the two wires from each other, but has become a conductor of electricity. As the electricity flows, the heat generated lights up the glass, the propane torch can be removed, and the glass continues to glow very brightly.
A grape makes a great dipole antenna, and makes a great (small and safe) series of sparks in the microwave.
Passing a current through water makes hydrogen and oxygen, which fill a bubble that can be ignited.
An internally frosted, large light bulb is dipped into a fish tank of water, and the total internal reflection effect produces 'other-worldly' consequences to how the bulb looks in the water. The bulb goes from white to a silvery orb. Turning the bulb on, produces a similar, but more alluring effect.
A stream of air is used to levitate a small ball--and also a light bulb.
Passing a small electric current through a mechanical pencil lead causes it to glow brightly for several seconds.
You can push a knitting needle through a balloon if you take certain precautions.
A pencil lead and some batteries make a small plasma cutter that we use to etch a pattern in aluminum foil.
A piece of clear plastic shrinks and turns white with heat. Great way to use #1 containers!
A plastic frame can be used to create square--and other unusually shaped--bubbles