Answer: (4) heat of reaction
Explanation:
1) Activation energy is defined as the extra energy required by the reactants to cross the energy barrier in order to get converted to products.
2) Heat of fusion is the the heat required to convert 1 mole of the solid into liquid state at constant pressure.
3) Thermal energy is the energy possessed by an object by virtue of its temperature.
4) Heat of reaction is defined as the difference between the potential energy of the products and the potential energy of the reactants in a chemical reaction.
\(\Delta H=E_p-E_R\)
