Many thanks to student Alex Blackwood who filmed them using the Sony FS-700 camera, filming at 800 FPS.
The reaction of hydrogen gas with oxygen in the air to form water can be demonstrated by igniting a balloon filled with hydrogen gas. WARNING: audiences should be advised to cover/protect their ears because the resulting explosion can be very loud especially if the balloon is large enough. The chemical reaction taking place is:
2 H2(g) + O2(g) → 2 H2O(g)
Although this is a fairly simple reaction, it makes a fantastic learning tool and can be applied in several topics in chemistry and science in general. However, it must always be remembered that H2(g) is very flammable in air and explosive if confined and must be handled with care.