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🧲AP Physics 2
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🧲AP Physics 2

FRQ 4 – Qualitative/Quantitative Translation
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Unit 9: Thermodynamics
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FRQ Types & Units

Each FRQ type tests specific skills taught in particular units. Here's why certain units appear for each question type:

This mapping reflects College Board's exam structure - each FRQ type tests specific skills that are taught in particular units.

Practice FRQ 1 of 201/20

4. A rigid, sealed container holds n=0.50 moln = 0.50\ \text{mol}n=0.50 mol of a monatomic ideal gas, as shown in Figure 1. The gas is initially in thermal equilibrium with a reservoir at temperature T1=300 KT_1 = 300\ \text{K}T1​=300 K and has pressure P1=1.0×105 PaP_1 = 1.0× 10^5\ \text{Pa}P1​=1.0×105 Pa. The container is then placed in thermal contact with a hotter reservoir at temperature T2=600 KT_2 = 600\ \text{K}T2​=600 K until the gas reaches a new thermal equilibrium. Assume the gas remains ideal, the container volume remains constant, and the gas temperature is uniform at all times.

Figure 1. A rigid, sealed, constant-volume container holding n = 0.50 mol of monatomic ideal gas is heated by thermal contact with a hotter reservoir, raising the gas temperature from T1 = 300 K to T2 = 600 K (with initial pressure P1 = 1.0×10^5 Pa).

Figure 1
A.

A student claims that when the gas is heated from T1T_1T1​ to T2T_2T2​ at constant volume, the pressure increases because gas atoms collide with the container walls more frequently and with greater average momentum change per collision.

Indicate whether the student's claim is correct or incorrect. Without manipulating equations, justify your answer by referencing how increasing temperature changes the microscopic motion of the gas atoms and how that microscopic motion is related to the pressure exerted on the container walls.

B.

Derive an expression for the energy QQQ transferred to the gas by the hot reservoir as the gas warms from T1T_1T1​ to T2T_2T2​ at constant volume. Express your answer in terms of nnn, T1T_1T1​, T2T_2T2​, and physical constants, as appropriate. Begin your derivation by writing a fundamental physics principle or an equation from the reference information.

C.

Indicate whether the expression you derived in part B is or is not consistent with the student's claim in part A that the pressure increases when the gas is heated at constant volume. Briefly justify your answer by referencing how pressure depends on temperature for an ideal gas at constant volume.

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Free Response Question Practice

This practice environment simulates the AP AP Physics 2 Free Response Questions section. Here are some guidelines:

  • Read each question carefullybefore responding. Pay attention to command verbs like "identify," "explain," "analyze," or "evaluate."
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Tip: Answer all parts of each question. Partial credit is often available, so even if you are unsure, provide what you know.