The Second Law of Thermodynamics: Entropy and Heat IV
1. The Second Law of
Entropy and Heat, plus
By Shawn P. Shields, Ph.D.
This work is licensed by Shawn P. Shields-Maxwell under a Creative Commons
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2. Recall: The Second Law of Thermodynamics
The total entropy change for any
spontaneous process is positive
Positional disorder- The distribution of
molecules (particles) in space (related to
Thermal disorder- The distribution of
energy states among the particles
(related to temperature)
3. Entropy and Heat
Heat flows occurs spontaneously
from hot objects to colder ones.
Objects in contact
will end up at the
4. Predicting the Sign of S for Changes in
Entropy increases with increasing
As heat is added to the system,
the number of accessible energy
5. Example: Entropy of Fusion (Sfus)
The entropy associated with fusion
qrev is the heat associated with a
6. Heating and
“A Generalized Plot of Entropy versus
Temperature for a Single Substance
steadily with T.
Large jumps are
7. S for Phase Transitions
S increases as a substance melts.
In the solid, particles are essentially
fixed into place.
As the substance melts, a larger
number of positions are accessible to
the molecules (in the liquid state)