This Weeks Experiment - Heating a Balloon
Taken from the original version of experiment #13, written May 15, 1997.

You can see the video version of this experiment at:
http://www.krampf.com/experiment_vid.html

*WARNING* This experiment uses fire. Be safe, use common sense, and be sure there is an adult in the room, so you have someone to blame if something goes wrong.

This is a variation of an old, Victorian parlor trick, but even after more than 100 years, it is still just as amazing. In Victorian times, the experiment was done by folding a calling card (much like a modern business card) into a square container. When the paper container was filled with water, it could be held over a candle to boil the water without the paper catching fire.

For this modern version, you will need:

a candle
matches or a lighter
several balloons
water

Blow up one of the balloons and tie it off. Light the candle. Now, what do you think would happen if you held the balloon in the candle flame? Lets try it and see. Carefully, hold the balloon just at the top of the candle flame. BANG! Just as you probably predicted, the balloon pops and it blows out the candle.

Now, lets try that again, but this time with a twist. Instead of filling the balloon with air, lets make it a little more fun. Lets try the experiment with a water balloon! Carefully stretch the mouth of the balloon over a water faucet and slowly fill the balloon with water. Then blow in a little air and tie it off.

At this point, work over a sink or outside, just in case things don't work as they should. Once again, light the candle, and hold the balloon over the candle, just at the top of the flame. What happens? You probably expected the balloon to pop, getting you wet. Instead, the bottom of the balloon turned black, but it did not pop. Why?

Understanding the Science
Water is very good at soaking up heat. Because the balloon is very thin, heat energy passes through it quickly heating the water on the inside. As the water near the flame starts to get hot, it rises, letting cooler water take its place to soak up more heat. This process lets the water balloon absorb a tremendous amount of heat without popping.

The black stuff on the balloon is the element carbon. It did not come from the balloon. Instead, it was deposited by the candle flame. The balloon has not been burned or damaged.

The idea of absorbing heat to control it is a very useful idea indeed. Firefighters use it to protect themselves while they are fighting fires. The radiator in your car absorbs heat from the engine to keep it from overheating. Heat sinks in computers absorb heat to protect delicate circuits. The idea even applies to ice cream, which absorbs the heat from hot fudge sauce, cooling it enough so you can eat it without burning your mouth. That sounds like an experiment worth trying.

Have a wonder-filled week!