is converted to the internal energy of the gas, as evidenced by a rise in gas
temperature, creating a higher level of molecular disorder in the container.
This process is quite different from raising a weight since the organized
paddle-wheel energy is now converted to a highly disorganized form of
energy, which cannot be converted back to the paddle wheel as the rota-
tional kinetic energy. Only a portion of this energy can be converted to work
by partially reorganizing it through the use of a heat engine. Therefore,
energy is degraded during this process, the ability to do work is reduced,
molecular disorder is produced, and associated with all this is an increase in
entropy.
The quantityof energy is always preserved during an actual process (the
first law), but the quality is bound to decrease (the second law). This
decrease in quality is always accompanied by an increase in entropy. As an
example, consider the transfer of 10 kJ of energy as heat from a hot medium
to a cold one. At the end of the process, we still have the 10 kJ of energy,
but at a lower temperature and thus at a lower quality.
Heat is, in essence, a form of disorganized energy, and some disorganiza-
tion (entropy) flows with heat (Fig. 7–25). As a result, the entropy and the
level of molecular disorder or randomness of the hot body decreases with
the entropy and the level of molecular disorder of the cold body increases.
The second law requires that the increase in entropy of the cold body be
greater than the decrease in entropy of the hot body, and thus the net
entropy of the combined system (the cold body and the hot body) increases.
That is, the combined system is at a state of greater disorder at the final
state. Thus we can conclude that processes can occur only in the direction
of increased overall entropy or molecular disorder. That is, the entire uni-
verse is getting more and more chaotic every day.Entropy and Entropy Generation in Daily Life
The concept of entropy can also be applied to other areas. Entropy can be
viewed as a measure of disorder or disorganization in a system. Likewise,
entropy generation can be viewed as a measure of disorder or disorganiza-
tion generated during a process. The concept of entropy is not used in daily
life nearly as extensively as the concept of energy, even though entropy is
readily applicable to various aspects of daily life. The extension of the
entropy concept to nontechnical fields is not a novel idea. It has been the
topic of several articles, and even some books. Next we present several ordi-
nary events and show their relevance to the concept of entropy and entropy
generation.
Efficient people lead low-entropy (highly organized) lives. They have a
place for everything (minimum uncertainty), and it takes minimum energy
for them to locate something. Inefficient people, on the other hand, are dis-
organized and lead high-entropy lives. It takes them minutes (if not hours)
to find something they need, and they are likely to create a bigger disorder
as they are searching since they will probably conduct the search in a disor-
ganized manner (Fig. 7–26). People leading high-entropy lifestyles are
always on the run, and never seem to catch up.
You probably noticed (with frustration) that some people seem to learn
fast and remember well what they learn. We can call this type of learning348 | Thermodynamics
HOT BODY
80 °C(Entropy
decreases)COLD BODY
20 °C(Entropy
increases)HeatFIGURE 7–25
During a heat transfer process, the net
entropy increases. (The increase in the
entropy of the cold body more than
offsets the decrease in the entropy of
the hot body.)
FIGURE 7–26
The use of entropy (disorganization,
uncertainty) is not limited to
thermodynamics.
© Reprinted with permission of King Features
Syndicate.
WshGASTFIGURE 7–24
The paddle-wheel work done on a gas
increases the level of disorder
(entropy) of the gas, and thus energy is
degraded during this process.