Why does the match float?

So i saw a trick the other day where you place a coin under a match, and that match is leaning against another match that is standing upright, if you light the center of the leaning match on fire then it will start to float and you can remove the coin, what i am asking is how this works. Here is an example:

begins at 2:36

http://ift.tt/1ja1kGj