Exploding bubbles of hydrogen

Soap bubble becomes a fireball.

Scientific name: Soap bubble filled with hydrogen ignites.


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Wear eye protection goggles and gloves. Hydrogen gas is very flammable and yields explosive mixtures with air. Perform this demonstration outdoors. Perform away from all flammable materials.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

2Al + 6H2O + 2NaOH → 2NaAl(OH)4 + 3H2

2H2+O2 → 2H2O

Step-by-step instruction

WARNING! This experiment is dangerous! You should NOT perform this at home. ONLY carry out this experiment, if you are a trained chemist, and you understand local safety and legal requirements, which are required to perform such experiments

  1. Put several pieces of aluminum foil in a flask.
  2. Pour sodium hydroxide solution in this flask. Sodium hydroxide solution is often sold as a drain cleaner.
  3. Reaction producing hydrogen begins.
  4. Fit the flask with a rubber stopper and gas delivery tube.
  5. Dip the tube into the soap solution.
  6. Light up a splinter.
  7. Pull the tube and let the soap bubble form. It is filled with hydrogen which is lighter than air and hops off.
  8. Hold the splinter to the bubble. The bubble rapidly catches fire.

Scientific background

Aluminum is a very reactive metal but it does not react with water because it is covered with a protective layer of aluminum oxide. Sodium hydroxide will remove the aluminum oxide cover layer and aluminum starts to react with water:

2Al + 6H2O + 2NaOH → 2NaAl(OH)4 + 3H2

In this reaction hydrogen gas is produced. Soap bubbles are formed by the gas passing through the soap solution. Thus they are filled with hydrogen. Hydrogen is a very flammable gas and easily ignites when you hold the burning splinter to the bubble. When it burns it looks like a fireball. The reaction is:

2H2+O2 → 2H2O


Published on 14 March 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst