Hydrogen Bubbles

Alternate titles:

Soap Bubbles, Exploding Bubbles

Purpose:

To demonstrate that the density of hydrogen is less than that of air.

Materials:

• Long candle or long lighter
• Rubber/vinyl tubing
• Y-shaped tubing adaptor
• Plastic/metal tub/tray

Reagents:

• Dawn (or other) dish soap
• Glycerol
• O_2(g)
• H_2(g)

Hazards and PPE:

• Caution audiences to protect their own ears.
• Use a long candle or lighter to ingite bubbles to avoid injury to hands/arms.
• Wear approved safety goggles and gloves.
• Wear ear protection, as exploding gas bubbles will go off with a bang.

Protocol:

Preparation

1. Prepare the soap bubble solution (this can be reused for many future iterations)
   1. Add 2.52L DI H₂O to a 4L plastic container/bottle.
   2. Add 300mL dish soap.
   3. Add 180mL glycerol.
   4. Mix well.
   5. Allow to rest until bubbles dissipate.
2. Connect H₂ and O₂ gas lines to a y-shaped adaptor, with several feet of tubing connected to the other end of the adaptor.
3. Fill a tray/pan with enough bubble solution to comfortably submerge the full diamater of the tubing used.
4. Immediately prior to demonstration, open/activate H₂ and O₂ gas lines if applicable to your setup.

Demonstration

1. Light a long candle/taper if using one.
2. Submerge the end of the combined gas line to bubble the gas mixture into the solution.
3. As bubbles float away, ignite them with the candle/lighter.

Additional Notes:

• Experiment with different ratios of hydrogen and oxygen gas to achieve varying bubble results!
• If the bubbles are heavy enough, you can instead use a hand soaked in water to scoop up a handful of bubbles and ignite this. Perform this version only with pure hydrogen bubbles.

Disposal:

• Remaining solution can be poured back into the labeled soap bubble container and reused, or poured down the sink.

Reactions:

• 2H_2(g) + O_2(g) → 2H₂O_(g) + ΔH

Citations:

1. This demo adapted from the demo library of the Chemistry department at the University of Illinois at Urbana-Champaign.

Videos:

• Exploding Hydrogen Bubbles in Your Hands

  Flinn Scientific

  This video differs from the protocol in two ways. First, a chemical method of hydrogen gas generation is used, which is perfectly viable for this demonstration. Second, this presenter shows only the version of the demonstration involving the conflagration of a handful of bubbles. The other listed video demonstrates what they look like ignited in midair.

• Exploding Hydrogen Bubbles

  Periodic Videos

  This video excludes nearly all of the setup of the demonstration, but exhibits beautifully and in slow-motion the ignition of airborne hydrogen bubbles.