Thermodynamics and statistical mechanics
Connect heat, work, temperature, entropy, microscopic populations, and phase changes. Test engines, refrigerators, and equilibrium claims against explicit assumptions.
Prerequisite: High-school science and basic algebra. No calculus or prior thermodynamics required. Thirteen lessons and 26 illustrated exercises connect macroscopic balances to microscopic counting and equilibrium. Eleven interactive models compare heat capacities, transport, gas states and paths, entropy changes, cyclic devices, melting, and energy populations. The models separate physical constraints from material assumptions and measured performance.
Lessons
- 1
Define the system and its temperature
Temperature predicts thermal contact, but it does not count how much energy an object contains.
- 2
Keep heat, work, and internal energy separate
Use conservation to calculate what changes, then determine a shared temperature from heat capacities.
- 3
Distinguish heat transfer from heat storage
Conduction, fluid motion, and radiation explain transfer rates. Heat capacity explains storage.
- 4
Connect gas pressure to microscopic motion
An ideal gas links amount, volume, and absolute temperature. Its internal energy still needs a molecular model.
- 5
Calculate work along a path
The area under a pressure-volume path gives quasi-static expansion work. Equal endpoints can have different heat and work transfers.
- 6
Count microscopic alternatives
A coarse description can represent many microscopic arrangements. Counting explains why some macrostates are more likely.
- 7
Account for entropy across the boundary
Energy conservation does not determine the direction of heat flow. Entropy accounting adds the missing constraint.
- 8
Derive the limit on heat-engine work
A cyclic engine can conserve energy and still violate the second law. Reservoir temperatures set a stricter limit.
- 9
Explain refrigerators and heat pumps
Work can move heat from cold to hot. Performance greater than one is possible because most delivered heat is moved, not created.
- 10
Separate temperature rise from phase change
Added energy can change how much material is solid or liquid without raising temperature.
- 11
Predict equilibrium energy populations
A thermal bath favors lower-energy states, while the number of states at each energy also matters.
- 12
Choose the right equilibrium criterion
A system can lower its own free energy while increasing total entropy. Constraints and composition determine the correct criterion.
- 13
Audit a thermodynamic claim
Check boundaries, units, conservation, entropy, and rates before accepting a mechanism or performance number.