I am a mechanical engineering student, but have yet to take thermodynamics. For months now, I have been reading up on thermo and am actually quite interested in it. However, I am still quite confused with the concept of entropy. Its pretty much the consencus that the "disorder" explanation is not true, and it is the measure of energy that is wasted or unavailable to do useful work in a system. Can someone explain how this concept of disorder arises from the mthematically definition and if there is any truth to it?