Playbook
Thermodynamics
84 q - 1.92/paper - 21% HARD. The first law is cheap; the processes page holds the HARD at 31%.
- Questions in the bank
- 84
- q/paper (2024–25 papers)
- 1.92
- Tagged HARD
- 21%
- Subtopics
- 3
Strand: Long Tail
When you’ll see it
Heat supplied and work done by a gas, an isothermal or adiabatic change, a p–V diagram, or a heat engine or refrigerator.
How this chapter is tested
84 q at 1.92 a paper, 21% HARD. First Law, Internal Energy, and Work-Heat Relations (37 q, 11%) is the cheap page: ΔQ = ΔU + ΔW, with ΔU = nC_vΔT whatever the process.
The HARD sits on Isothermal, Adiabatic, Isobaric, and Isochoric Processes (36 q, 31%): PV^γ = constant for an adiabatic change, work in an isothermal expansion nRT ln(V₂/V₁), and work as the area under a p–V curve — enclosed by a cycle, positive if the cycle runs clockwise.
Carnot Engine, Efficiency, and Refrigerator is small (11 q, 27%): η = 1 − T₂/T₁ with temperatures in kelvin, and the coefficient of performance of a refrigerator T₂/(T₁ − T₂).
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
First law
ΔQ = ΔU + ΔW. ΔU depends only on ΔT: nC_vΔT.
The four processes
Isothermal ΔU = 0; adiabatic ΔQ = 0 and PV^γ = constant; isochoric ΔW = 0; isobaric ΔW = PΔV.
Work from a p–V diagram
Work = area under the curve; for a cycle, the enclosed area, clockwise positive.
Heat engines
η = 1 − T₂/T₁ (kelvin). Refrigerator COP = T₂/(T₁ − T₂).
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Letting ΔU depend on the path
Internal energy is a state function: two processes between the same end states have the same ΔU, however different their Q and W.
Celsius in the efficiency
η = 1 − T₂/T₁ needs kelvin. An engine between 27 °C and 327 °C has η = 1 − 300/600 = 50%, not 92%.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Thermodynamics notesDrill every thermodynamics question
84 questions from the bank, scoped to 3 bundled subtopics.
Drill one subtopic at a time
The 3 subtopics this playbook covers, in catalog order.
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Often paired with this one — the technique, the trap or the taxonomy overlaps. Drill these next.