Answer:
Do you want me to give you the definition in math, science or just what a product means because there's different types.
True becuase the substance changed into another substance which is a example of a chemical reaction.
The thing that governs whether a reaction is exothermic is the energy given out / used up to break / form the bonds in the reaction.
<span>When two substances react, the bonds in those substances first break up, releasing energy, before re-forming in a different way, taking in energy. The nature of the bonds that are broken up and reformed determines whether more energy is given out (exothermic) or taken in (endothermic)</span>