So, naturally we find Gray Matter's demonstration of fiery hydrogen bubbles pretty awesome. But the most interesting part is the reason behind the demonstration. Did you know the same gas that heats your house can also make it explode?
Gray Matter explains why:
"Without oxygen, propane can't burn. You could light a match inside a propane tank, and nothing would happen. Furnaces control the rate of burning by mixing propane with air slowly as it burns. But premix large amounts, and the results are very different.
To show this, I filled soap bubbles with hydrogen gas and lit them with a lighter. (I used hydrogen because it makes the bubbles float, so they're safer to light at a distance. Propane bubbles would sink.) Pure-hydrogen bubbles burn quietly as the hydrogen mixes with air and burns over several seconds. Fill the bubbles with a mixture of hydrogen and oxygen, though, and what was a gentle whoosh becomes a chest-thumping bang. When fuel and air mix in advance, the entire volume of gas burns in a fraction of a millisecond -- which is to say, it explodes."