Physics › Section J · Thermodynamics › Topic J.6
Entropy and its statistical meaning
Ice melts in a warm drink, but a lukewarm drink never sorts itself into ice and hot liquid. Entropy is the quantity that captures this one-way behaviour, and counting the microscopic arrangements of a system shows why it almost always increases.
In this topic
- A new quantity for the second law
- Defining a change in entropy
- Worked example: melting ice
- Entropy is a state function
- Worked example: heat flowing downhill
- The second law in entropy form
- Entropy and energy that can no longer do work
- Worked example: counting coin arrangements
- Why the second law is about probability
- Boltzmann's formula
- Common mistakes to avoid
- Key takeaways
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