← Physics 2 syllabus

United StatesPhysics 2

Unit 9: Thermodynamics

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

Why does heat flow only from hot to cold, and what does entropy say about the direction of natural processes?

Topic 9.6 Entropy and the Second Law of Thermodynamics: relate entropy to disorder and apply the second law to the direction of energy transfer.
A focused answer to AP Physics 2 Topic 9.6, covering entropy as a measure of disorder and energy dispersal, the second law of thermodynamics, the irreversibility of natural processes, why heat flows only from hot to cold, and the impossibility of a perfectly efficient engine, with full worked examples.
10 min answer →

How does energy conservation apply to a gas, and how do you read the work done from a PV diagram?

Topic 9.4 First Law of Thermodynamics and PV Diagrams: apply the first law to track internal energy, heat and work, and read work as the area on a PV diagram.
A focused answer to AP Physics 2 Topic 9.4, covering the first law of thermodynamics as energy conservation, internal energy and its link to temperature, work done by and on a gas as the area on a PV diagram, the four named processes (isothermal, isobaric, isovolumetric, adiabatic), and the sign conventions, with full worked examples.
12 min answer →

How does the random motion of countless atoms produce the measurable pressure and temperature of a gas?

Topic 9.1 Kinetic Theory of Gases: relate the pressure and temperature of an ideal gas to the average kinetic energy and motion of its atoms.
A focused answer to AP Physics 2 Topic 9.1, covering the kinetic theory model of an ideal gas, how molecular collisions produce pressure, the link between absolute temperature and average translational kinetic energy, the relation between root-mean-square speed and temperature, and the assumptions of the model, with full worked examples.
11 min answer →

Why do different materials need different amounts of energy to heat up, and how fast does heat conduct through a slab?

Topic 9.5 Specific Heat and Thermal Conductivity: apply Q = mc(delta T) for heating and the conduction rate equation for steady heat flow.
A focused answer to AP Physics 2 Topic 9.5, covering specific heat capacity and the relation Q = mc(delta T), calorimetry with conservation of energy, the rate of heat conduction through a material, and the role of thermal conductivity, with full worked examples.
11 min answer →

How are the pressure, volume, temperature and amount of a gas tied together in a single law?

Topic 9.3 The Ideal Gas Law: apply PV = nRT (and PV = N k_B T) to relate the state variables of an ideal gas.
A focused answer to AP Physics 2 Topic 9.3, covering the ideal gas law in both molar and molecular forms, the meaning of each state variable, the use of absolute temperature, the special-case proportionalities (Boyle, Charles, Gay-Lussac), and the before-and-after ratio method, with full worked examples.
11 min answer →

What does temperature really measure, and why does heat always flow from hot to cold until equilibrium?

Topic 9.2 Thermal Equilibrium and Temperature: define temperature through average kinetic energy and explain heat transfer and thermal equilibrium between systems in contact.
A focused answer to AP Physics 2 Topic 9.2, covering temperature as a measure of average kinetic energy, the direction of heat flow from hot to cold, thermal equilibrium and the zeroth law, the three mechanisms of heat transfer (conduction, convection, radiation), and the distinction between heat and temperature, with full worked examples.
10 min answer →