In which equation does the term "heat" represent heat of fusion?

(1) NaCl (s) + heat - - >NaCl (l)

(2) NaOH (aq) + HCl (aq) - - >NaCl (aq) + H2O (l) + heat

(3) H2O (l) + heat - - > H2O (g)

(4) H2O (l) + HCl (g) - - >H3O + (aq) + Cl - (aq) + heat

Heat of Fusion is defined as the energy required to turn a liquid into a solid, or said phase changing latent heat. In this case the only choice that represents that phase change is (1). Where the heat removed to turn a liquid of a substance into it's solid form is instead added to excite the bonds and liquify it. Yet, heat of fusion (s) - > (l)

is still the same as going from liquid to solid just one is adding and the other is removing, respectively.