Need help teaching the basics?

Sometimes I’m lucky just to get my teeth brushed in the morning, let alone design an experiment that illustrates Einstein’s photoelectric effect for my 7-year old son.  Luckily, though, YOU don’t need to reinvent the wheel (or the light bulb), because here’s a quick list of cheap and easy experiments that really drive home the basic principles in physical science.

I was thinking of titling it Quality Science in a Hurry on a Shoestring Budget.  But what do you think?
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Higher pressure always pushes: Blow hard over the top of a sheet of paper and watch it fly up to the horizontal. (This is the basic principle in all aerodynamics.)

Like charges repel; opposites attract: Rub your head with a balloon and hold the charged balloon near your head so the positively charged hair sticks to the negatively charged balloon. (Maxwell’s equations.)

Moving charges have magnetic and electric fields: Wrap wire around a nail and connect to power to create a simple electromagnet that can pick up paper clips. (Maxwell’s equations.)

Light travels like a wave but interacts like a particle: Wave: Grab red, green, and blue-tinted flashlights and make shadow puppets on a white wall.  Or dab two fingers into a pond of still water and watch the waves interfere with each other.  Particle: Charge a glow-in-the-dark object with a camera flash. The energy in (flash) causes the electrons to bump into a higher orbit, but when the flash shuts off, the electrons relax back down to their regular state and emit a photon (in a different wavelength, or color of light… which is the color of your glowing object)…or use a homemade electroscope and hit it with both a red light, then a blue.  You’ll find that the red light doesn’t knock the electrons out of orbit (and cause the two foil strips to separate), but the blue certainly does! (Duality principle of light.)

Three states of matter: solid, liquid, and gas: Grab a can of soda. The tin can is the solid, the drink is the liquid, and the bubbles are the gas.

In a system, Stuff In equals Stuff Out: Energy in = Energy out: a marble rolling down a hill.  The amount of energy the marble had while at rest at the top of the hill (potential energy) turns into kinetic energy while it zips to the bottom. Momentum in = Momentum out: Place your thumb partway over the end of a garden hose. The water shoots out faster because the same amount of “stuff” has to pass through the exit. When the exit area decreases, less mass can pass through at one time, so the velocity increases.  (These are the basic conservation laws: conservation of every, conservation of momentum, conservation of mass.)

Objects at rest stay at rest unless acted upon by an external force: Place an object on the floor and wait very carefully for it to move on its own. Ready for more action? Kick it… and there’s your external force. (This is the first law of physical motion.)

For every action, there is an equal and opposite reaction: Hold a balloon between your fingers and let it go. Note which way the air inside the balloon goes relative to the balloon itself initially. (This is the third law of physical motion.)

Four fundamental forces of nature: strong, weak, gravitational, and electromagnetic: The protons and neutrons on an atom are glued together via the strong force (which is broken when you dump salt into water and measure the temperature increase).  Gravitational forces happen every time you throw a ball.  Make the electromagnet mentioned above experiment to demonstrate electromagnetic forces. (Skip the weak force for now.)

Heat flows from hot to cold: Leave a cup of hot coffee out on the table.  Does it heat up or cool down after 5 minutes?  (This has to do with the second law of thermodynamics.)

For the Ideal Gas Law: When temperature increases, pressure and volume increase:  Blow up a balloon and stick it in the freezer.  When volume decreases, pressure increases – Connect two syringes together with tubing and press one plunger.[/am4show]