Where does the energy change in chemical reaction come from?

According to the nature of the reaction, chemical reaction must be accompanied by the exercise of old chemical bonds and the formation of new chemical bonds. The rupture of old chemical bonds will absorb energy, and the formation of new chemical bonds will release energy, so chemical reactions will inevitably be accompanied by quantitative changes.

Judging from the total energy changes of reactants and products. When the total energy of reactants is higher than that of products, there is energy release in chemical reactions. When the total energy of reactants is lower than that of products, there is energy absorption in chemical reactions.