Hydrogen vs. Helium Balloon

We're all familiar with helium balloons and how they float.  Why do they float?  They float because helium is less dense (lighter) than the surrounding air, so the helium gas in the balloon causes the balloon to float upward.  The balloon will continue to float upward until it's blocked by something or the air density matches that of the balloon.

What happens to the helium balloon when you bring a flame to it?  It pops as normal, as you probably expected.  But what happens when you fill the balloon with hydrogen instead of helium?  My daughter and I went to a science show recently and saw this in action.

The hydrogen balloon will also float as hydrogen gas is lighter than the surrounding air.  When you bring a flame nearby something drastically different happens.  Hydrogen is very flammable, so instead of just popping, the gas inside the hydrogen balloon ignites into a big fire ball with a very loud boom!  This is definitely something you do NOT try at home!

Here's a link to a YouTube video showing something very similar to what we saw at the science show.

Slow Motion Hydrogen Balloon Explosion

Very impressive!  The demonstrators did this several times and each time it was just as impressive as the first!