Two identical copper disks, Disk A at an initial temperature of 80 °C and Disk B at an initial temperature of 20 °C, are placed on a thin insulating stand inside a rigid, perfectly insulated chamber that prevents any exchange of energy or matter with the surroundings. No phase changes occur and the disks remain in thermal contact with each other until equilibrium is reached.
(a) Describe the final equilibrium state of the two-disk system in terms of temperature and macroscopic observables.
(b) Using the concept of entropy, explain why energy flows in the direction you described in part (a) rather than the reverse direction.
(c) State whether the total entropy of the isolated two-disk system increases, decreases, or remains constant during the process, and justify your answer qualitatively without performing numerical calculations.