A fireproof balloon is a great magic trick that will amaze the audience who knows balloons are fragile and would pop if heated.
A simple activity with a dramatic result that may inspire young kids to wanting to know more about STEM related subjects.
- 2 Balloons
- 60 ml of Water
- Matches or lighter
- Safety goggles
What Mystery Are We Solving?
Why is it that when a normal balloon is held over a fire or in the sun, the heat pops the balloon – but if it is filled with water the balloon doesn’t pop when held over a flame?
A simple water balloon experiment that is relatively safe to perform by younger kids. Adult supervision is recommended to prevent kids accidentally swallowing balloon pieces or burning their fingers with the candle.
- Light a candle.
- Blow up a balloon and tie the end.
- Hold the air-filled balloon over the candle and time how quickly it pops.
- Now add a little water to the second balloon or water balloon.
- Blow up the balloon.
- Now hold the balloon close to the candle flame
How Does The Fireproof Balloon Work?
When a balloon is too long in the sun it pops. The gas (air) inside the balloon expands adding pressure to the rubber of the balloon. The rubber has its limits of stretching and the balloon bursts.
When you hold a balloon filled with air over a candle, the air is a poor heat conductor. The rubber cannot withstand the heat and the balloon bursts.
A water balloon isn’t burst when held to the flame. The heat is transferred to the water which has a very high heat capacity. Water’s heat capacity is four times higher than air. It requires much more energy to separate the water molecules.
A convection current occurs when the heat is transferred through the rubber to the water. The water above the flame heats up and rises and is replaced with cool water. The constant interchanging of water molecules creates the convection current. The balloon rubber is cooled by the water. The water makes the balloon “fireproof”. (If the flame were hot enough, you could pop the balloon.)