Entropy of isolated systems never decreases
Second law of thermodynamics
Entropy of isolated systems never decreases
The second law of thermodynamics establishes entropy as a physical property of a thermodynamic system. It predicts whether processes are forbidden despite obeying the first law of thermodynamics and provides criteria for spontaneous processes. For instance, while the first law allows a cup to fall and break, the second law denies the reverse process of fragments spontaneously reassembling.
Example
Consider a cup falling off a table and breaking. The first law of thermodynamics allows this process. However, the second law of thermodynamics states that the entropy of the isolated system (the cup and the table) never decreases, meaning the fragments cannot spontaneously come back together and jump onto the table.
Remember this
Understanding this principle is crucial for predicting the direction of natural processes and understanding the limitations of energy conversion systems.
Text adapted from Wikipedia, licensed under CC BY-SA 4.0.
Related concepts
Demon (thought experiment)
Maxwell's demon challenges the Second Law of Thermodynamics by suggesting information can decrease entropy
Uncertainty principle
Landauer's principle resolves: erasing one bit of information dissipates at least kT ln 2 of energy
Equipartition theorem
Equipartition theorem: Each degree of freedom contributes ½kT of energy at thermal equilibrium
Boltzmann's entropy formula
Boltzmann's entropy formula: S = k ln Ω
universality means in phase transitions
Universality in phase transitions implies identical critical exponents across diverse systems
Symmetry (physics)
Symmetry leads to energy conservation
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