1. For a reaction to occur, energy must be
to break chemical bonds.
O A released
OB converted
OC absorbed

For a reaction to occur, energy must be absorbed to break chemical bonds

Explanation:

Reactions can be classified as chemical reaction, nuclear reaction, thermal reaction. So in these three reaction types, the nature of energy will only be varying.

But in order to execute a reaction, there should be breaking of existing bonds and then formation of new bonds. So for breaking of the bonds of reactants, energy should be absorbed from the surrounding.

Then the extra energy will be released after forming the products. Thus, the process of absorption of energy will lead to endothermic process and the process of releasing of energy will lead to exothermic reaction. So for a reaction to occur, energy must be absorbed to break the chemical bonds.