2. What's the nature of internal energy? Int S K+U In Ini Sum of the kinetic energy associated with random motions of the atoms and the potential energy associated with the forces between the atoms Ch 13 Energy III: Conservation of energyCh.13 Energy III: Conservation of energy 2. What’s the nature of “internal energy”? Sum of the kinetic energy associated with random motions of the atoms and the potential energy associated with the forces between the atoms. Eint = Kint +Uint