Answer the following question given this paragraph: 

Nuclear changes occur with a simultaneous release of energy. Where does this energy come from? If we could precisely measure the masses of the reactants and the products of a nuclear reaction, we would notice that the amount of mass drops slightly in the conversion from reactants to products. Consider the following nuclear reaction, in which the molar mass of each species is indicated to four decimal places:.


Q: Nuclear changes occur with a simultaneous release of what, and a slight drop in mass?


A:
energy