&gt;However, I do not see how this has anything to do with the concept of entropy.<p>in short - entropy of the system with lower gravitational potential is higher (<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Entropic_gravity" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Entropic_gravity</a>). When oil is mixed into water, the thermodynamic entropy &quot;St,mix&quot; of oil&#x2F;water system is higher than  &quot;St,unmixed&quot; while the entropy &quot;Sg,mix&quot; of the gravitational system of oil&#x2F;water&#x2F;Earth is lower when mixed than the &quot;Sg,unmixed&quot; of the unmixed case. In case of bad solubility, like oil in water, we have [&quot;St,mix&quot; - &quot;St,unmixed&quot; &lt; &quot;Sg,unmixed&quot; - &quot;Sg,mix&quot;] and thus system on its own will evolve toward unmixed state.