> In it's gaseous state Hydrogen is very volitile. In the fuel cell cars however Hydrogen is kept in its liquid state at very low temperatures.

Notice that you have used it's and its for exactly the same purpose. This message courtesy of the grammar curmudgeon.

The liquid hydrogen becomes gaseous when it warms, in which case it is highly dangerous (if there is any oxidizer in the neighborhood). And since liquid hydrogen has to be kept very cold compared to our ordinary surroundings, its warming is very easy.