-2 round balloons
-Several matches or a butane lighter
Inflate one balloon and tie it closed. Pour about 1/4 cup of water in another balloon, inflate it, and tie it shut. Light a match and hold it under the first balloon. Allow the flame to touch the balloon. The balloon will burst. Light another match and hold it directly under the second balloon. The balloon does not break.
The flame heats the rubber of both balloons. The rubber of the first balloon becomes so hot that it becomes too weak to resist the pressure of the air inside of the balloon. With the second balloon, the water absorbs most of the heat from the flame. The rubber of the balloon does not become as hot. Water is a particularly good absorber of heat-the balloon does not break.