Baby, it’s cold outside! This time of year, it’s important to stay warm however you can. Hosing yourself off with water is not the best way to do this, of course; nor is just lighting random things on fire. But, with this nifty demonstration, you can put the two together to show students the excellent heat absorbing properties of water, and how this can affect other materials. Plus, there’s open flame involved, which should help hold the attention of even the most ADDlepated kids in your class.
For this science demo, you will need the following supplies: two identical balloons, a lighter, and some water. Inflate the first balloon with air and tie it closed, as you do. Skillfully pour about a quarter cup of water into the second balloon, inflate it to the same size as the first balloon, and tie it closed, as well.
Flick your Bic and hold it under the air-only balloon. Pop! It will burst faster than you can say, “Hey, I bet if I hold a flame under this balloon it will pop before I can finish this sentence.”
Repeat the previous step with the air-and-water balloon. No pop. Why not? An unsolvable mystery, that.
Wait—No It Isn’t! Read On for Science
The first balloon popped because the rubber material from which it’s made became very hot while in contact with the flame. This heat weakened the rubber, and the air pressure inside broke on through to the other side.
The second balloon got hot, too, but it didn’t break because the water in it absorbed most of the flame’s heat. This took the heat-stress off the rubber, preventing it from bursting. Ergo, water has been proven to be a better absorber of heat that air.
Water and fire best air and fire. Not sure how earth fits into this equation, but please feel free to conduct a few experiments of your own and let me know who the ultimate elemental grand champion is.