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. Classically, this would be a state of motionlessness, but quantum uncertainty dictates that the particles. The third law of thermodynamics has two important consequences: it defines the sign of the entropy of any substance at temperatures above absolute zero as positive, and it provides a fixed reference point that allows us to measure the absolute entropy of any substance at any temperature. This is a state at which the enthalpy and entropy of a cooled ideal gas reaches its minimum value, taken as 0. This process also results in a more disordered universe. Absolute zero is the coldest theoretical temperature, at which the thermal motion of atoms and molecules reaches its minimum.

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.

What is entropy at absolute zero