Entropy in thermodynamics is a measure of disorder, affecting chemical reactions and phase changes. It's denoted as S and measured in J/K, reflecting the number of microscopic configurations in a system. Standard entropy (S°) is crucial for predicting substance behavior under standard conditions. Factors like temperature and phase changes influence entropy, with equations available for calculating changes during reactions. The second law of thermodynamics relates to reaction reversibility and entropy's tendency to increase.
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Entropy measures the degree of disorder or randomness in a system
Macroscopic State
Entropy reflects the number of microscopic configurations a system can have given its macroscopic state
Measurement in Joules per Kelvin
Entropy is typically measured in joules per kelvin (J/K)
Entropy is a measure of the system's thermal energy per unit temperature that is not available for doing work
Entropy increases during phase transitions such as melting or vaporization
An increase in temperature generally causes an increase in entropy
A reaction that produces more moles of gas than it consumes will likely result in an increase in entropy
Standard entropy values are essential for calculating the entropy changes that accompany chemical reactions
The change in entropy during a chemical reaction is the difference in entropy between the final and initial states of the system
The second law of thermodynamics states that the entropy of an isolated system will tend to increase over time
Ideal gases exhibit specific entropy behaviors that can be predicted using simple equations
The entropy change for an ideal gas undergoing expansion or compression can be calculated using a specific equation
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Entropy symbol and units
Symbolized as S, measured in joules per kelvin (J/K).
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Entropy's relation to disorder
Measures degree of disorder; higher entropy indicates more disorder.
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Third law of thermodynamics
States entropy of perfect crystal at absolute zero is zero.
