The above diagram shows the problem description. I have to find the final temperature distribution after thermal equilibrium. I am assuming that the thermal energy is conserved but not the temperature.(Correct me if I am wrong) Energy of the materials at initial state is (Refer Image) For material 1 - m.Cp.T = 100*1*45 W = 4500W For material 2 - m.Cp.T = 200*1*50 W = 10000W So the system would achieve equilibrium when the energy in both material are same i.e. 7250W If that happens Material 1 would be at a temperature of 72.5 C Material 2 would be at a temperature of 36.25 C I know that this method is wrong indeed. But can anyone explain me why we would conserve the temperature instead of energy of the system??