Tian2
The Tian2 Study Library AP Edition · Tian2 Editorial Bureau
Volume I · MMXXVI AP Physics 2: Algebra-Based
Library› AP Physics 2: Algebra-Based› Unit 9: Thermodynamics
⁂   AP Physics 2: Algebra-Based · Unit 9

9. Thermodynamics

15–18% of the AP exam. 11 key topics. 4 common errors analyzed.

15–18% exam weight

Unit 9: Thermodynamics

Unit 9 (Thermodynamics) extends the AP Physics 2 curriculum. Emphasize conceptual justification: FRQ scoring rubrics award points for physical reasoning stated in precise sentences.

Key topics in this unit

  1. Kinetic theory of gases and microscopic model of pressure
  2. Ideal gas law (PV = nRT)
  3. Internal energy and temperature
  4. First law of thermodynamics (ΔU = Q + W or Q − W)
  5. Second law of thermodynamics and entropy
  6. Thermodynamic processes: isothermal, adiabatic, isobaric, isochoric
  7. PV diagrams: work as area under curve, interpretation of processes
  8. Heat engines and efficiency (e = |W|/|Q_H|)
  9. Carnot efficiency (e_C = 1 − T_C/T_H)
  10. Heat transfer: conduction, convection, radiation
  11. Thermal equilibrium and zeroth law

Common errors — what the rubric penalizes

These are the most frequently penalized mistakes on AP exam FRQs and MCQs. Review each before your next practice session.

Common error

Applying the wrong sign convention for work (W done BY the system vs. ON the system) in the first-law equation, leading to ΔU errors in multi-step process problems

Common error

Reading PV diagrams incorrectly — confusing which direction around a cycle produces positive net work vs. negative net work, or failing to identify area under curve as work

Common error

Misapplying Carnot efficiency: using Celsius temperatures instead of Kelvin, or conflating heat-engine efficiency with coefficient of performance for refrigerators

Common error

Conflating entropy with heat or disorder qualitatively — FRQ justifications scored on precision; vague statements like 'entropy increases because it gets hotter' do not earn credit without linking to the second law and spontaneous processes

Study checklist

  • Can you list all key topics from memory without this page?
  • Have you worked through at least one FRQ-style question per topic?
  • Can you explain each common error above — and why the correct answer differs?
  • Have you reviewed the relevant College Board CED section and formula sheet entries?
Electric Force, Field, and Potential →
← Back to AP Physics 2: Algebra-Based
Our worked solutions and practice questions are original instructional content created by Tian2 AP. They are aligned to the concepts and skills described in College Board’s Course and Exam Description and are not reproductions of, or affiliated with, College Board’s official materials.