From Thermodynamics to Economics and Ecology - Thanatia: The Destiny of the Earth's Mineral Resources - page 65

walls. Meanwhile, in an open system, its energy will be the sum of all work done,
heat absorbed or released and energy variations (due to the transfer of matter).
Once aware of the energy balance, one can save on measurements. If one wants to
assess the energy of what goes in and what goes out in an open system, only those
flows which are easy to obtain need to be measured, as the most di cult one will be
calculated by closing the balance, as stipulated by the First Law. The evolution of
science, technology and industry throughout the 20th century are indebted to this
Law, mainly because it is an equality equation.
In short, energy can neither be created, nor destroyed. It can only be trans-
formed. This is in effect the Law of Conservation of Energy, or the First Law of
Thermodynamics which many find familiar.

3.2.2 The Second Law

As seen above, for work a relationship exists between an intensive property and
its conjugated extensive property, e.g. expansion work is equal to pressure times
volume change. Heat equally has an associated intensive property: temperature.
Hence, its extensive conjugated property can be defined as:
dS = Q
T

(3.2)

This property is known as Entropy. Whilst entropy does not appear to have
anything particularly impressive about it, other than being the conjugated pro-
perty of temperature, it has a fundamental role in Nature and the continuation of
life. Entropy, like energy, is a state function and can be obtained by knowing the
intensive properties of a system, i.e., pressure, temperature and composition. The
fundamental idea behind it is that everything degrades or becomes dispersed.
So how does entropy relate to degradation? Unlike humans, Nature is not pur-
poseful in its actions. Man designs machines for domesticating “her” forces and
attempts to convert them into useful effects, as is the case of pumps used to revert
the natural flow. Left alone, sooner or later fluids will stop flowing, warm bodies
will get colder, pure substances will become impure. Everything will degrade spon-
taneously. Degradation may thus be controlled and slowed to a certain extent but
in the long run it cannot be avoided. This is an experimental fact and constitutes
the Second Law of Thermodynamics.
So if everything degrades yet energy is conserved, one is forced to admit that
there are some forms of energy which are more useful and less degraded than oth-
ers. During the act of tightening a screw on a wall, the screw becomes warm. That
warmth cannot be used to restore the wall to its initial state. Mechanical energy
has been exchanged for thermal energy and with time the screw will have, during
the cooling process, contributed a little to the heating up of the surrounding envi-
ronment. The mechanical energy applied to the screw came from food. One has
simply converted food's chemical energy into an insignificant heating of the atmos-
phere, a screw on the wall and waste. It is thus a given fact that any form of noble