Unit 1: Thermodynamics
Physics 2 · Unit 1 · Paper 2

Thermodynamics unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1Paper 2Paper 3
Each paper is built from this unit’s 45 terms and is the same for everyone, so a teacher can assign “Unit 1, Paper 2” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.
Suggested time 37 min 34 points0/17 attempted
1

Maxwell-Boltzmann distribution

2

Adiabatic

3

Work on a PV diagram

4

Reading engine versus refrigerator off a PV loop

5

Zeroth law

6

Coefficient of performance

7

Temperature vs thermal energy

8

Average kinetic energy per molecule

9

What internal energy depends on

10

Isochoric

11

RMS speed

12

Three modes of heat transfer

Short answer 1. Define or explain: Internal energy of an ideal gas

3 pts

Short answer 2. Define or explain: Kelvin is not optional

3 pts

Short answer 3. Define or explain: First law of thermodynamics

3 pts

Short answer 4. Define or explain: Root-mean-square speed

3 pts

Free response

10 pts

MATHEMATICAL ROUTINES (Question 1, 10 points). A sample of n moles of a monatomic ideal gas is in a large, sealed, thermally conducting container of fixed volume. A small sphere of mass mS (volume negligible next to the container's) is inside, initially in thermal equilibrium with the gas. The gas is initially in State X with pressure P and volume V. The gas is heated until it reaches State Y with pressure 3P, and the sphere is again in thermal equilibrium with the gas. The total energy transferred to the sphere during the heating is QS. (Figure 2 shows the Maxwell-Boltzmann speed distribution for State X — number of atoms per unit speed versus atom speed.) For B: an insulated container holds a liquid of mass mL and specific heat cL. The original sphere (mass mS < mL, specific heat cS < cL) is submerged in the liquid, starting hotter than the liquid; they reach thermal equilibrium, with temperature-change magnitudes |ΔTL| and |ΔTS|.

A(i). Describe the curve on Figure 3 that could represent the atoms-per-unit-speed distribution for State Y, compared with the State X curve.

A(ii). Derive an expression for the change ΔT in gas temperature from State X to State Y, in terms of n, P, V, and physical constants, as appropriate.

A(iii). Derive an expression for the specific heat cS of the sphere, in terms of n, mS, P, V, QS, and physical constants, as appropriate.

B. Indicate whether |ΔTS| is greater than, less than, or equal to |ΔTL|, and justify with conceptual reasoning beyond algebraic solutions.