If gasoline turns from liquid to a high pressure gas

[Qaiphyx]

in internal combustion engines, how do they run hydrogen in these engines like the BMW hydrogen car when hydrogen combusts into H2O?

 

[Curl]

Its not about the phase transition but the chemical reaction that makes it work.

 

[daumphys]

Combustion heat makes the gas which is introduced into the engine expansion. At that moment the engine generates work. Q=m Cp del T + del (PV). And del (PV) makes work. Ideal work is like this.
W= Int (V_int to V_final) P dV