Combustion of Hydrogen
Materials
Balloon filled with Hydrogen (big bang)
Balloon with about 1/3 Oxygen and 2/3 Hydrogen (bigger bang)
Yardstick
Matches
Tape
Earplugs
2 weights with string to tie to balloons
Goggles and gloves
Procedure
Balloons filled with hydrogen gas are tethered to a weight with a string and lit with a match taped to a yardstick.
Reactions:
2H2 (g) + O2 --> 2H2O (g)
The Change in Enthalpy (delta H)
dH = -232 kJ/mole
Note on Safety: Both balloons in this demo should be behind the large plex shield (to protect the audience from small pieces of balloon) and the the balloons should be sized (about 4 inches in diameter is what I use for the fuel/oxygen balloon) so that the bang is not loud enough to cause ringing in the ears.
When I do this type of demonstration I also warn the audience to cover their ears for the "loud" explosion and light off the balloon on the count of 3... [and I do it at the end of the period because it brings down lots of chalk dust which can irritate eyes & lungs].