A science teacher inflated three 30 cm (12″) helium-quality balloons with gas. One balloon had oxygen, another balloon had hydrogen, and a third balloon had a combination of oxygen and hydrogen. The students were requested to predict which balloon would give the loudest ‘bang’ when ignited.
One at a time, each balloon was attached with a string to the taps at the teacher’s sink, with the balloon approximately midway between the taps and the ceiling. The teacher approached the balloon with a flame attached to the end of a one-metre ruler. Once the flame touched the balloon, the gas inside the balloon exploded. The explosion in each case was sudden and brief.
A student suffered serious ear damage as a result!!!