Curriculum Notes 

In addition to its obvious crowd appeal, detonating a hydrogen balloon can be used to demonstrate combination, redox, formation, and exothermic reactions and activation energy. The video link below downloads a RealMedia file of a recent shuttle launch. The main rocket engine of the shuttle burns hydrogen. Allow about 5 minutes for this demo.

One day of lead time is required for this project.

Discussion 

The formula for the combustion of hydrogen is:|
$\ce{2H2(g) + O2(g) -> 2H2O(g)}$ 

Materials 

• balloon filled with hydrogen gas
• candle taped to the end of a 1 meter long stick
• butane lighter to light candle
• hearing protection
• goggles

Procedure 

• Put on goggles and hearing protection.
• Light the candle that is taped to the end of the stick.
• Dim the lights (optional).
• Instruct the class to put their fingers in their ears. Do not proceed until you have observed that all of the students are complying.
• Standing as far away as possible, hold the flame up to the bottom half of the balloon using the candle on a stick.
• BOOM! The hydrogen in the balloon will explode in a ball of flame.

Safety Precautions 

• You will be standing rather close to an explosion. Be sure to wear safety goggles and hearing protection.
• Make sure that the nearest observer is at least 5m away.
• Check to be sure that students have actually put their fingers in their ears.
• Make sure that there are no flammable materials in the vicintiy of the demo. Know the location of the nearest fire extinguisher.

Prep. Notes 

Fill the balloon from the hydrogen tank in the lab. Be sure to wear goggles because it is possible that the dry gas flowing into the rubber balloon could generate static electricity and a spark could ignite the hydrogen.