Hi. If there are two objects A and B, the temperature of A is TA, the temperature of B is TB, and my questions are: 1). If TA = TB, their internal energy (which is the kinetic energy plus some other forms of energy) might not be the same. In this case, A and B are in thermal contact. Since TA = TB, no heat flow happens. Am I correct? The internal energies of A and B remain the same although the internal energy of A may be larger than the internal energy of B. 2). If TA > TB, heat flow is from A to B. Here, I know that the internal energy of B will increase (TB might not be increased though in the case of phase transition). However, how about the change of the internal energy of A? Is that all the heat flow from A is from the kinetic energy of A's molecules? or some of the heat flow come from the kinetic energy of A and some of it come from the other forms of energy of A such as the potential energy? thx.