Entropy and the distribution of energy
The Second Law of Thermodynamics
the Second Law states that the operation of any spontaneous process leads to an (overall) increase of entropy . Our experi-
ence of this law is so intricately woven into the fabric of everyday life that we are scarcely aware of its existence, but its
impact on science is nonetheless profound. the expansion of a gas is a spontaneous process involving an increase of
entropy: a gas never spontaneously contracts into a smaller volume. Water never runs uphill. applying heat to an electric
fire will never generate electricity. all of these impossible events, were they to occur, would bring about a reduction of
entropy and therefore violate the Second Law.
entropy is lowest when energy is concentrated in one part of a system. this is a characteristic of all of the energy resources
that we exploit: water retained behind a hydroelectric dam, chemical energy stored in a tank of gasoline or in a charged battery,
nuclear energy in a uranium fuel rod, etc. entropy is highest when energy is evenly distributed throughout the system being
considered, and in such circumstances it cannot be put to good use. Spontaneous (entropy-increasing) changes are always
accompanied by a degradation in the 'quality' of energy, in the sense that it becomes dispersed more widely and uniformly.