If you blank water it turns into
Blank to form gas.

If you heat a liquid like water up even more (like if you put it in a pot on the stove), then the molecules will move around so fast that they can't even hold on to each other at all. When this happens, all of the molecules go flying apart and become a gas (like when you boil water to make steam).
So you basically need to heat the water to turn it into gas.

Answer : The reaction will be .

Now as the given enthalpy of  is -242 KJ
and the enthalpy of is -609 KJ.

According to the formula of Hess's summation, ΔHreaction= (ΣΔHproducts)-(ΣΔHreactants)

Therefore, ΔHreaction = [ + ] -

on substituting the values and omitting the value for oxygen as it is in gaseous state we get,
ΔHreaction = [0 + (2 X -242)] - [2 X -609] 

on solving we get, ΔHreaction = 734 KJ.