Fireproof Balloon

Age

Elementary School

Format

Stage Show

Materials

   Two round balloons
   Several matches
   Water 

Safety Precautions

Science Theatre demonstrators must keep the safety of themselves and their audience in mind at all times. All Science Theatre demonstrators must have read through the Safety Training page. The ST Safety Box with first aid kit, fire extinguisher, etc. should always be available to demonstrators. Always wear safety gloves, glasses, and a labcoat if handling chemicals; always perform potentially dangerous demonstrations at a safe distance from the audience; and always keep a very close eye on any volunteers you call from the audience. be careful when handling matches to avoid burning yourself or causing accidental fires.

Preparation

Inflate one of the balloons and tie it closed. Place 60 milliliters (1/4 cup) of the water in the other balloon, and then inflate it and tie it shut.

Demonstration

Light a match and hold it under the first balloon. Allow the flame to touch the balloon. What happened? The balloon breaks, perhaps even before the flame touches it.

Light another match. Hold it directly under the water in the second balloon. Allow the flame to touch the balloon. What happens to the balloon? The balloon doesn't break. You may even see a black patch of soot form on the outside of the balloon above the flame.

What to Say

Why does the balloon with no water break in the flame? The flame heats whatever is placed in it. It heats the rubber of both balloons. The rubber of the balloon without water becomes so hot, that it becomes too weak to resist the pressure of the air inside the balloon.

How does the balloon with water in it resist breaking in the flame? When water inside the balloon is placed in the flame, the water absorbs most of the heat from the flame. Then, the rubber of the balloon does not become very hot. Because the rubber does not become hot, it does not weaken, and the balloon does not break.

Why It Is

Water is a particularly good absorber of heat. It takes a lot of heat to change the temperature of water. It takes ten times as much heat to raise the temperature of 1 gram of water by 1C than it does to raise the temperature of 1 gram of iron by the same amount. This is why it takes so long to bring a teakettle of water to boil. On the other hand, when water cools, it releases a great deal of heat.

Real Life Examples

This is why areas near oceans or other large bodies of water do not get cold in the winter as areas at the same latitude further inland.