- Matches / lighter
Water is a great substance for soaking up heat. The thin balloon allows the heat to pass through very quickly and warm the water. As the water closest to the flame heats up, it begins to rise and cooler water replaces it at the bottom of the balloon. This cooler water then soaks up more heat and the process repeats itself. In fact, the exchange of water happens so often that it keeps the balloon from ever popping! The soot on the bottom of the balloon is actually carbon. The carbon was deposited on the balloon by the flame, and the balloon remains undamaged.