When hydrogen is heated with oxygen, water is formed.
More water forms, more energy release . In the following experiment, you will find out the ratio of hydrogen to oxygen produce the greatest amount of water, as well as energy.

When the hydrogen to oxygen ration is 2:1, the sound of explode of the balloon is the loudest.
It matches the theory that water is made up of two hydrogen atoms and one oxygen atom. So called H₂O.