![]() But what happens if the temperature goes to zero, T → 0 T → 0? It turns out this is not a question that can be answered by the second law.Ī fundamental issue still remains: Is it possible to cool a system all the way down to zero kelvin? We understand that the system must be at its lowest energy state because lowering temperature reduces the kinetic energy of the constituents in the system. For any other thermodynamic system, when the process is reversible, the change of the entropy is given by Δ S = Q / T Δ S = Q / T. The second law of thermodynamics makes clear that the entropy of the universe never decreases during any thermodynamic process. Discuss how this result can be related to an increase in disorder of the system. In Example 4.7, the spontaneous flow of heat from a hot object to a cold object results in a net increase in entropy of the universe. The net result is an increase in entropy and an increase in the disorder of the universe. ![]() However, this ordering process is more than compensated for by the disordering of the rest of the universe. After all, a single cell gathers molecules and eventually becomes a highly structured organism, such as a human being. You might suspect that the growth of different forms of life might be a net ordering process and therefore a violation of the second law. The increased disorder of the ice more than compensates for the increased order of the reservoir, and the entropy of the universe increases by 4.6 J/K. However, the reservoir’s decrease in entropy is still not as large as the increase in entropy of the ice. Although the change in average kinetic energy of the molecules of the heat reservoir is negligible, there is nevertheless a significant decrease in the entropy of the reservoir because it has many more molecules than the melted ice cube. The molecular arrangement has therefore become more randomized. The ice changes from a solid with molecules located at specific sites to a liquid whose molecules are much freer to move. ![]() This process also results in a more disordered universe. If we considered only the phase change of the ice into water and not the temperature increase, the entropy change of the ice and reservoir would be the same, resulting in the universe gaining no entropy. The entropy of the universe therefore is greater than zero since the ice gains more entropy than the reservoir loses. ![]()
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