Consider the phase change H2O (l) → H2O (g). This equation describes the phase change from liquid water to steam. Think about the heat flow that is necessary for this change to take place. What do you predict about the process?

Heat is absorbed during the phase change. The bonds are stronger when the water is in the liquid phase in order to break these bonds energy should be supplied. Hope this answers the question. Have a nice day. Feel free to ask more questions.