Chapter
Entropy and Free Energy
14.1
Spontaneous Processes
14.2 Entropy
• A Qualitative Description of Entropy
• A Quantitative Definition of Entropy
14.3
Entropy Changes in a System
• Calculating ?Ssys • Standard Entropy, S°
• Qualitatively Predicting the Sign
of ?S°
sys
14.4
Entropy Changes in the Universe
• Calculating ?Ssurr • The Second Law
of Thermodynamics • The Third Law of
Thermodynamics
14.5
14.6
Predicting Spontaneity
• Gibbs Free-Energy Change, ?G
• Standard Free-Energy Changes, ?G°
• Using ?G and ?G° to Solve Problems
Thermodynamics in Living Systems
The illustration shows the process by which a polypeptide chain in a biological
cell folds into a three-dimensional structure called a protein. Although the original
polypeptide chain can assume any number of configurations, the protein, if it is to
function properly, must adopt a specific arrangement. Thus, the folding of a protein
is accompanied by a decrease in system entropy. According to the second law of
thermodynamics, any spontaneous process must result in an increase in the entropy
of the universe. It follows, therefore, that there must be an increase in the entropy of
the surroundings greater in magnitude than the decrease in entropy associated with
the protein folding. In fact, the folding of a protein is exothermic and does indeed
cause an increase in entropy of the surroundings via the spreading out of the energy
produced by the process.
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