Vaporization of water at its boiling point is represented on an energy diagram with liquid water at 0 kJ and water vapor at +40.7 kJ per mole. Which classification best describes this phase change?
a) Exothermic, ΔH<0
b) Endothermic, ΔH<0
c) Endothermic, ΔH>0
d) Isothermal, ΔH=0