Final answer:
The resulting heat from a reaction is the sum of the bonds broken minus the sum of the bonds formed, which is called the enthalpy change (ΔH). If more energy is consumed than released, ΔH is positive (endothermic reaction). Conversely, if more energy is released than consumed, ΔH is negative (exothermic reaction).
Step-by-step explanation:
The resulting heat from a reaction is equal to the sum of the bonds broken minus the sum of the bonds formed. The difference between the total heat absorbed (for bond breaking) and the total heat released (for bond making) during a chemical reaction is known as the enthalpy change (ΔH). When we calculate the enthalpy change, we add together the average energies of the bonds broken in the reactants and subtract the average energies of the bonds formed in the products. If more energy is required to break bonds in the reactants than is released when new bonds form in the products, the reaction is endothermic, and ΔH is positive. Conversely, if less energy is required to break bonds in the reactants than is released when new bonds form in the products, the reaction is exothermic, and ΔH is negative.