The entropy of an isolated system always do what when natural processes occur?
increase
if you mix hot and cold water and get warm water the entropy is higher, even if the energy did not change. The availability of that energy is what changed. Between a glass of hot water and a glass of cold water you can run an engine. However there is not much you can do with a glass of warm water alone even though the amount of heat energy is the same.
This is the trouble with OTEC (Offshore Thermal Energy Conversion) where the difference in temperature between deep ocean water and water at the surface (in tropics of course) can be used to run a turbine system and generate electricity or whatever. However the efficiency is low because although the surface water seems warm and the deep water cold, the difference in degrees Kelvin is just not very much so the efficiency stinks no matter what you do.
When natural processes occur in an isolated system, the entropy of the system always tends to increase. This is known as the second law of thermodynamics. The concept of entropy is a measure of the system's disorder or randomness.
To understand why entropy tends to increase in natural processes, let's consider an example. Imagine you have a box filled with gas molecules, and initially, all the gas is concentrated in one corner of the box. In this state, the system has low entropy because the gas molecules are highly ordered in a small region.
Now, if you were to remove the barrier dividing the box, the gas molecules would naturally spread out and occupy the entire volume of the box. This leads to an increase in the system's entropy because the gas molecules become more randomly distributed throughout the available space.
This example illustrates how natural processes tend to drive a system towards more probable, disordered states. While it is technically possible for the system to return to a lower entropy state, such occurrences are highly unlikely and require specific conditions or external intervention to take place.
To summarize, the second law of thermodynamics states that in an isolated system, the entropy tends to increase during natural processes as the system moves towards more disordered states.