By Teachers, For Teachers
As Halloween approaches, I try to use the holiday as an excuse to amaze my students with science demonstrations that capture their attention, challenge their expectations, and teach them a thing or two about physics, chemistry, or biology.
And, best of all, by using pretty common supplies they can share the amazement with their friends and families.
Here a list of my five favorite Halloween science demonstrations:
Using that staple of Halloween science--dry ice--we can create bubbles that appear to “hover”. All that you need is a small aquarium with a small amount of dry ice and warm water in the bottom. Give the carbon dioxide gas from the subliming dry ice to accumulate in the bottom of the aquarium. A layer of “fog” will be visible, but above that will be an invisible layer of gas that is heavier than air. Now, blow some ordinary bubbles (using, for example, bubble solution and a bubble wand) gently into the aquarium. Watch as the bubbles appear to float in the middle of the aquarium, held aloft by their density which is slightly lower that the surrounding carbon dioxide gas.
Black Light Magic
With the purchase of a standard black light--either a flashlight-style, special incandescent bulb, or a small fluorescent light--you can perform some pretty fantastic tricks. Try writing with standard highlighter on paper, skin, or even clothing, and using the ultraviolet-emitting black light to make the writing glow. Compose secret messages or draw cryptic symbols and let the light bring it to life. This works best in low light, such as a darkened porch on Halloween night.
Also, try shining the light on tonic water or laundry detergent.
Every sorcerer, wizard, and witch knows that a puff of smoke from your fingers can add some flair to your spell casting. It’s easy for any would-be magician to amaze his audience with the help of some glycerol, using the same process that allows fog machines to work. In fact, the best source of glycerol is a small bottle of fog machine liquid, rubbed on the middle finger and thumb. All that’s needed is some heat, generated by snapping one’s fingers, and *poof* you have a small puff of smoke.
The key to this trick is the combination of a soapy solution, dry ice fog, and a smooth-rimmed bowl. Start by putting a small amount of warm water in the bowl and adding a couple of pieces of dry ice and a glow stick for good measure. As the fog begins to form, take a piece of string slightly longer than the diameter of the bowl and soak it in a soapy solution. Drag the string across the edge of the bowl to create a film that stretches over the entire top of the bowl. Then, sit back and watch as a fog-filled bubble forms. Predict the future at your own risk.
The last trick is the easiest to pull off! All that you need is a normal latex balloon and a small nut from the hardware store. Place the nut inside the balloon and then inflate the balloon and tie a knot in the neck. Swirl the balloon by holding the knot at the top with one hand and moving the other end in a circular motion. As the nut begins to roll around in the inside surface of the balloon, you will hear an eerie sound that is reminiscent of an Irish banshee howling across the moors.
The best part about surprising folks this Halloween with these trick is explaining the science behind them. Education and entertainment all in one!
How do you bring Halloween into the classroom? Share in the comments section!