Entropy (usual symbol S) is also sometimes referred to as the law of entropy or as the second law of thermodynamics. In any system, the measure of this disorganisation or disorder is called entropy. The more ordered energy is, the more available it is to do useful work; this happens in a system when entropy is at a minimum. Clausius enhanced the first statement of the second law of thermodynamics in 1865 as “entropy always increases in a closed system.” In other words, other energies in an isolated (i.e., closed) system will change toward heat and disorder. In the second Law of thermodynamics states that for a chemical process to be spontaneous, there must be an increase in entropy.