AP Physics 2 Quiz: Thermal Energy Transfer And Equilibrium

20 questions · exam conditions

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Thermal Energy Transfer And EquilibriumQuestion 1 of 20

A student places a $25^\circ\text{C}$ glass beaker in direct contact with a $90^\circ\text{C}$ hot plate. The beaker is initially cooler than the hot plate, and they remain in contact until the beaker's temperature stops changing. Which statement best describes the thermal energy flow while they approach equilibrium?

Thermal energy flows from the beaker to the hot plate until both are at the same temperature.

No thermal energy flows because the beaker's temperature increases due to its material, not energy transfer.

Thermal energy flows from the hot plate to the beaker until their temperatures become equal.

Thermal energy flows equally in both directions, so the beaker's temperature stays at

25^\circ\text{C}

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AP Physics 2 Quiz

AP Physics 2 Quiz: Thermal Energy Transfer And Equilibrium

Practice Thermal Energy Transfer And Equilibrium in AP Physics 2 with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Thermal Energy Transfer And Equilibrium, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Physics 2.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Thermal energy flows from the beaker to the hot plate until both are at the same temperature.
No thermal energy flows because the beaker's temperature increases due to its material, not energy transfer.
Thermal energy flows from the hot plate to the beaker until their temperatures become equal. (correct answer)
Thermal energy flows equally in both directions, so the beaker's temperature stays at $25^\circ\text{C}$ .

Explanation: This question tests understanding of thermal energy transfer and equilibrium. The hot plate at 90°C is in contact with the glass beaker at 25°C, establishing a temperature gradient. Thermal energy flows from the higher temperature hot plate to the lower temperature beaker until they reach thermal equilibrium. Choice B incorrectly suggests no energy flows and attributes temperature change to the material itself rather than energy transfer, which violates the principle of energy conservation. The key concept is that thermal energy always flows from regions of higher temperature to regions of lower temperature through conduction.

Question 2

A student places a $40^\circ\text{C}$ steel sphere into a large bath of oil maintained at $20^\circ\text{C}$ . The sphere is fully submerged, and the bath is large enough that the oil temperature remains essentially constant. After a long time, the sphere's temperature becomes constant. At equilibrium, which statement best describes the thermal energy transfer between the sphere and oil?

Thermal energy continues flowing from the sphere to the oil because the sphere started hotter.
Thermal energy continues flowing from the oil to the sphere because the oil is denser.
No net thermal energy flows between the sphere and the oil because they are at the same temperature. (correct answer)
No thermal energy flows because equilibrium means both objects contain zero thermal energy.

Explanation: This question tests understanding of thermal energy transfer and equilibrium. Initially, the 40°C sphere transfers thermal energy to the 20°C oil bath until the sphere cools to 20°C. At equilibrium, both the sphere and oil are at the same temperature (20°C), so there is no net thermal energy flow between them. Choice A incorrectly suggests energy continues flowing based on initial conditions, but thermal energy flow requires a temperature difference. The fundamental concept is that at thermal equilibrium, no net energy transfer occurs because there is no temperature gradient.

Question 3

Two gases, A and B, are in thermal contact. The atoms of gas A have a higher average kinetic energy than the atoms of gas B. When an atom from A collides with an atom from B, which statement accurately describes the transfer of kinetic energy?

In every collision, kinetic energy will be transferred from the atom in A to the atom in B.
The transfer of kinetic energy is probabilistic, but on average, more energy is transferred from A to B than from B to A. (correct answer)
The probability of energy transfer from A to B is exactly equal to the probability of transfer from B to A.
In every collision, the atom with greater instantaneous speed will transfer energy to the atom with lesser instantaneous speed.

Explanation: Energy transfer in collisions is a statistical process. While a single collision could result in energy transfer from B to A (if a particularly fast atom from B hits a slow atom from A), the overall trend is governed by the average energies. Since gas A is hotter, it is far more probable that collisions will result in a net transfer of energy from A to B.

Question 4

A $0.10\,\text{kg}$ metal rod at $100^\circ\text{C}$ is pressed against a large wax block at $25^\circ\text{C}$ . The rod and wax are in direct contact, and the wax is thermally insulated from the surroundings. They remain in contact until the rod is no longer cooling. Which statement best describes the thermal energy flow during contact?

Thermal energy flows from the wax to the rod until both reach the same temperature.
No thermal energy flows because the rod cools due to radiation only, not contact transfer.
Thermal energy flows from the rod to the wax until they reach the same temperature. (correct answer)
Thermal energy flows equally in both directions at all times, so the rod cannot cool.

Explanation: This question tests understanding of thermal energy transfer and equilibrium. The metal rod at 100°C is pressed against wax at 25°C, creating a significant temperature difference. Thermal energy flows from the hotter rod to the cooler wax until they reach the same temperature. Choice D incorrectly claims energy flows equally in both directions at all times, which would prevent any temperature change and violates the principle of net energy flow from hot to cold. The fundamental rule is that thermal energy flows from higher to lower temperature until thermal equilibrium is established.

Question 5

Object X is at $25°C$ and object Y is at $75°C$ . They are brought into thermal contact inside a thermally isolated container. Which statement correctly describes the process as they approach thermal equilibrium?

The net energy transfer is from X to Y, and the final temperature will be greater than $75°C$ .
The net energy transfer is from Y to X, and the final temperature will be between $25°C$ and $75°C$ . (correct answer)
The net energy transfer is from X to Y, and the final temperature will be between $25°C$ and $75°C$ .
The net energy transfer is from Y to X, and the final temperature will be exactly $50°C$ .

Explanation: Thermal energy spontaneously flows from a region of higher temperature to a region of lower temperature. Therefore, energy is transferred from object Y to object X. The final equilibrium temperature must lie between the initial temperatures of the two objects.

Question 6

The spontaneous transfer of energy between two objects in thermal contact always occurs in a specific direction. Which of the following principles governs this directionality?

Energy is spontaneously transferred from the object with greater mass to the object with lesser mass.
Energy is spontaneously transferred from the object possessing greater total internal energy to the one with less.
Energy is spontaneously transferred from the object at a higher temperature to the object at a lower temperature. (correct answer)
Energy is spontaneously transferred from the object with a higher specific heat to the one with a lower specific heat.

Explanation: This is a consequence of the Second Law of Thermodynamics. The direction of spontaneous thermal energy transfer is determined by the temperature difference between the two objects, always flowing from hot to cold, regardless of their masses, internal energies, or specific heats.

Question 7

Two objects, A and B, are placed in an insulated container and are in thermal contact. Object A has a higher initial temperature than object B. Which of the following statements is true when the system reaches thermal equilibrium?

The net transfer of energy between objects A and B is zero. (correct answer)
Object A must have more internal energy than object B.
The total energy transferred from object B to object A is greater than the total energy transferred from A to B.
The temperature of object B is greater than the temperature of object A.

Explanation: By definition, thermal equilibrium is the state where there is no net flow of thermal energy between two systems in thermal contact. At this point, the rate of energy transfer from A to B equals the rate from B to A, resulting in a zero net transfer.

Question 8

A $1.0\,\text{kg}$ iron pan at $150^\circ\text{C}$ is placed in contact with $0.50\,\text{kg}$ cooking oil at $25^\circ\text{C}$ in an insulated setup so only pan and oil exchange energy. They are left until equilibrium. Which statement best describes the thermal energy flow?

Thermal energy flows from the oil to the pan until equilibrium because liquids transfer heat faster.
Thermal energy flows from the pan to the oil until both reach the same temperature. (correct answer)
No thermal energy flows at any time because equilibrium means both have zero thermal energy.
Thermal energy flows from the pan to the oil only after the oil becomes hotter than the pan.

Explanation: This question tests understanding of thermal energy transfer and equilibrium. The iron pan at 150°C is significantly hotter than the cooking oil at 25°C. When objects at different temperatures are in thermal contact, energy flows from the higher temperature object to the lower temperature object. Therefore, thermal energy flows from the hot pan to the cooler oil until both reach the same equilibrium temperature. Choice C incorrectly claims that equilibrium means zero thermal energy—equilibrium actually means equal temperatures, not zero energy. Always remember: thermal energy flows from regions of higher temperature to regions of lower temperature.

Question 9

A student places a $10^\circ\text{C}$ metal cube into $40^\circ\text{C}$ water in a well-insulated cup. The cube and water are left undisturbed until equilibrium is reached. Which statement best describes the thermal energy flow during this time?

Thermal energy flows from the cube to the water until both reach $10^\circ\text{C}$ .
Thermal energy flows from the water to the cube until both reach the same temperature. (correct answer)
No thermal energy flows because the cup is insulated, so temperatures remain fixed.
Thermal energy flows from the cube to the water because metals contain more heat than water.

Explanation: This question tests understanding of thermal energy transfer and equilibrium. The water at 40°C is warmer than the metal cube at 10°C, creating a temperature gradient that drives thermal energy transfer. Energy always flows from regions of higher temperature to regions of lower temperature, so thermal energy flows from the warmer water to the cooler metal cube. They will reach an equilibrium temperature between 10°C and 40°C. Choice D incorrectly suggests both reach 10°C, which would violate energy conservation since the water would lose more energy than the cube could absorb. Remember: thermal energy flows from hot to cold until temperatures equalize.

Question 10

A $2.0\,\text{kg}$ granite slab at $35^\circ\text{C}$ is pressed against a $2.0\,\text{kg}$ wooden board at $15^\circ\text{C}$ with no air gap, and the pair is insulated from the surroundings. After a long time, they reach equilibrium. Which statement best describes the thermal energy flow?

Thermal energy flows from the wood to the granite until equilibrium because wood is a better insulator.
No thermal energy flows because insulating materials prevent any energy transfer between objects.
Thermal energy flows from the granite to the wood until both reach the same temperature. (correct answer)
Thermal energy flows equally both ways at all times, so there is never a net flow.

Explanation: This question tests understanding of thermal energy transfer and equilibrium. The granite slab at 35°C is warmer than the wooden board at 15°C. When objects at different temperatures are in thermal contact, energy flows from the object at higher temperature to the object at lower temperature. Therefore, thermal energy flows from the warmer granite to the cooler wood until both reach the same equilibrium temperature. Choice A incorrectly suggests that being a better insulator reverses heat flow direction—insulation properties affect the rate of heat transfer, not its direction. Always apply: thermal energy flows from higher to lower temperature regions.

Question 11

A $0.30\,\text{kg}$ brass cylinder at $90^\circ\text{C}$ is clamped to a $0.30\,\text{kg}$ steel cylinder at $30^\circ\text{C}$ with thermal paste to ensure good contact. The pair is thermally isolated from the environment. Which statement best describes the thermal energy flow until equilibrium?

Thermal energy flows from the brass cylinder to the steel cylinder until they reach the same temperature. (correct answer)
Thermal energy flows from the colder steel cylinder to the warmer brass cylinder until both cool down.
Thermal energy flows from the steel cylinder to the brass cylinder because the masses are equal.
No thermal energy flows because thermal paste prevents energy transfer by filling air gaps.

Explanation: This question tests understanding of thermal energy transfer and equilibrium. The brass cylinder at 90°C is at a higher temperature than the steel cylinder at 30°C. When objects at different temperatures make thermal contact, energy always flows from the hotter object to the cooler object, regardless of their masses or materials. The thermal paste ensures good contact but doesn't change the direction of heat flow. Choice C incorrectly suggests thermal paste prevents energy transfer—it actually enhances it by eliminating air gaps. The key principle is: thermal energy flows from higher to lower temperature until equilibrium is reached.

Question 12

A $0.40\,\text{kg}$ lead sphere at $70^\circ\text{C}$ is dropped into a large insulated bath of oil initially at $20^\circ\text{C}$ . The sphere remains submerged until equilibrium is reached. Which statement best describes the direction of thermal energy flow?

Thermal energy flows from the oil to the lead sphere because the oil surrounds the sphere.
Thermal energy flows from the lead sphere to the oil until both reach the same temperature. (correct answer)
No thermal energy flows because the system is insulated, so the sphere stays at $70^\circ\text{C}$ .
Thermal energy flows from the colder oil to the hotter sphere until the oil reaches $70^\circ\text{C}$ .

Explanation: This question tests understanding of thermal energy transfer and equilibrium. The lead sphere at 70°C is at a higher temperature than the oil bath at 20°C. When objects at different temperatures are in thermal contact, energy always flows from the hotter object to the cooler one. Therefore, thermal energy flows from the hot lead sphere to the cooler oil until they reach the same equilibrium temperature. Choice C incorrectly claims insulation prevents all energy flow—insulation prevents energy exchange with the surroundings, not between the sphere and oil. The principle remains constant: thermal energy flows from regions of higher temperature to lower temperature.

Question 13

A sealed, rigid container holds liquid water at $60^\circ\text{C}$ . A metal spoon at $10^\circ\text{C}$ is submerged and the container is insulated from the room. After a long time, the spoon and water reach equilibrium. Which statement best describes the thermal energy flow during the process?

Thermal energy flows from the spoon to the water until both reach the same temperature.
Thermal energy flows from the colder spoon to the warmer water because metals transfer heat better.
No thermal energy flows because the container is sealed, so the spoon cannot gain energy.
Thermal energy flows from the water to the spoon until both reach the same temperature. (correct answer)

Explanation: This question tests understanding of thermal energy transfer and equilibrium. In this scenario, the water at 60°C is at a higher temperature than the metal spoon at 10°C. Thermal energy always flows from regions of higher temperature to regions of lower temperature, regardless of the materials involved. Therefore, thermal energy flows from the warmer water to the cooler spoon until both reach the same equilibrium temperature. Choice D incorrectly suggests that heat flows from cold to hot because metals are good conductors—this reverses the fundamental principle of heat flow. Remember: thermal energy flows from higher to lower temperature until thermal equilibrium is achieved.

Question 14

A sealed container holds two metal spheres in contact: sphere X at $40^\circ\text{C}$ and sphere Y at $90^\circ\text{C}$ , with no heat exchange to the outside. Which statement best describes the thermal energy flow?

At equilibrium, thermal energy flows equally both ways while temperatures remain different.
No thermal energy flows because the container is sealed, so temperatures remain fixed.
Thermal energy flows from X to Y until both spheres reach the same temperature.
Thermal energy flows from Y to X until both spheres reach the same temperature. (correct answer)

Explanation: This question tests understanding of thermal energy transfer and equilibrium. When two objects at different temperatures are in contact, thermal energy flows from the higher temperature object to the lower temperature object. Sphere Y at 90°C is hotter than sphere X at 40°C, so thermal energy flows from Y to X. This transfer continues until both spheres reach the same equilibrium temperature. Choice D incorrectly suggests equal flow maintains different temperatures, showing a misconception about what equilibrium means—it requires equal temperatures, not equal flows. To solve heat flow problems: compare temperatures, then apply the rule that energy flows from hot to cold.

Question 15

A $50\ \text{g}$ piece of wax at $55^\circ\text{C}$ is placed in contact with a $200\ \text{g}$ metal block at $15^\circ\text{C}$ inside an insulated box. Which statement best describes the thermal energy flow?

No thermal energy flows because the wax is a poor conductor, so its temperature changes without transfer.
Thermal energy flows from the colder metal to the warmer wax because the metal has larger mass.
Thermal energy flows from the metal block to the wax until both reach the same temperature.
Thermal energy flows from the wax to the metal block until both reach the same temperature. (correct answer)

Explanation: This question tests understanding of thermal energy transfer and equilibrium. When objects at different temperatures come into contact, thermal energy flows from the higher temperature object to the lower temperature object regardless of their masses or materials. The wax at 55°C is hotter than the metal block at 15°C, so thermal energy flows from the wax to the metal block. This continues until both reach the same equilibrium temperature. Choice C incorrectly claims no energy flows due to poor conductivity, confusing the rate of transfer with whether transfer occurs at all. Remember: thermal energy always flows from hot to cold until equilibrium, though the rate may vary.

Question 16

A glass beaker at $90^\circ\text{C}$ is placed in contact with a large metal plate at $30^\circ\text{C}$ in an insulated enclosure. Which statement best describes the thermal energy flow until equilibrium is reached?

Thermal energy flows from the colder plate to the hotter beaker until both reach the same temperature.
No thermal energy flows because the enclosure is insulated, so contact does not matter.
Thermal energy flows from the plate to the beaker until both reach the same temperature.
Thermal energy flows from the beaker to the plate until both reach the same temperature. (correct answer)

Explanation: This question tests understanding of thermal energy transfer and equilibrium. When objects at different temperatures make contact, thermal energy flows from the hotter object to the cooler object. The glass beaker at 90°C is hotter than the metal plate at 30°C, so thermal energy flows from the beaker to the plate. This flow continues until both reach the same equilibrium temperature. Choice C incorrectly states energy flows from cold to hot, demonstrating a fundamental misconception about the direction of spontaneous heat flow. To determine flow direction: identify temperatures, then remember thermal energy flows from hot to cold until equilibrium.

Question 17

A $0.20\ \text{kg}$ copper block at $80^\circ\text{C}$ is placed in contact with a $0.30\ \text{kg}$ aluminum block at $20^\circ\text{C}$ on an insulated table. Which statement best describes the thermal energy flow as they reach equilibrium?

No thermal energy flows because the table is insulated, so temperatures can change without energy transfer.
Thermal energy flows in both directions equally at all times, so the temperatures stay at $80^\circ\text{C}$ and $20^\circ\text{C}$ .
Thermal energy flows from the aluminum to the copper until both blocks reach the same temperature.
Thermal energy flows from the copper to the aluminum until both blocks reach the same temperature. (correct answer)

Explanation: This question tests understanding of thermal energy transfer and equilibrium. When two objects at different temperatures come into contact, thermal energy always flows from the higher temperature object to the lower temperature object. In this case, the copper block at 80°C is hotter than the aluminum block at 20°C, so thermal energy flows from the copper to the aluminum. This flow continues until both blocks reach the same equilibrium temperature, at which point the net energy transfer stops. Choice D incorrectly suggests equal flow in both directions maintains the original temperatures, revealing a misconception that equilibrium means no change rather than no net flow. Remember: thermal energy flows from higher to lower temperature until thermal equilibrium is reached.

Question 18

A hot ceramic mug at $90^\circ\text{C}$ is placed in contact with a room-temperature countertop at $22^\circ\text{C}$ ; both are left until equilibrium. Which statement best describes the thermal energy flow?

No thermal energy flows because solids cannot exchange thermal energy through contact.
Thermal energy flows from the mug to the countertop, but the mug's temperature increases.
Thermal energy flows from the countertop to the mug until both reach the same temperature.
Thermal energy flows from the mug to the countertop until both reach the same temperature. (correct answer)

Explanation: This question tests understanding of thermal energy transfer and equilibrium. When a hot object contacts a cooler object, thermal energy flows from the higher temperature object to the lower temperature object. The ceramic mug at 90°C is much hotter than the countertop at 22°C, so thermal energy flows from the mug to the countertop until they reach thermal equilibrium. Choice D incorrectly suggests that the mug's temperature could increase while losing energy, violating conservation of energy and revealing a fundamental misconception about heat flow direction. Remember that thermal energy flows from higher to lower temperature until equilibrium is reached.

Question 19

A $0.10\,\text{kg}$ ice cube at $0^\circ\text{C}$ is placed in $0.40\,\text{kg}$ of liquid water at $25^\circ\text{C}$ in an insulated cup until equilibrium. Which statement best describes the net thermal energy flow?

Net thermal energy flows from the ice to the water until both reach the same temperature.
Net thermal energy flows from the water to the ice only if the final temperature is above $25^\circ\text{C}$ .
Net thermal energy flows from the water to the ice until both reach the same temperature. (correct answer)
No net thermal energy flows because the ice is at $0^\circ\text{C}$ , so it cannot absorb energy.

Explanation: This question tests understanding of thermal energy transfer and equilibrium. When ice at 0°C is placed in warmer water at 25°C, thermal energy flows from the higher temperature water to the lower temperature ice. This energy transfer first melts the ice (phase change at 0°C) and then raises the temperature of the resulting water until thermal equilibrium is reached. Choice C incorrectly suggests that ice at 0°C cannot absorb energy, revealing a misconception that objects at phase transition temperatures cannot receive thermal energy. The key principle is that thermal energy flows from higher to lower temperature until equilibrium, including during phase changes.

Question 20

A beaker of water at $60^\circ\text{C}$ is poured into a foam cup containing water at $20^\circ\text{C}$ ; the cup is covered and reaches equilibrium. Which statement best describes the net thermal energy flow?

No net thermal energy flows because both samples are water, so temperature equalizes without transfer.
Net thermal energy flows from the $20^\circ\text{C}$ water to the $60^\circ\text{C}$ water until their temperatures match.
Net thermal energy flows from the $60^\circ\text{C}$ water to the $20^\circ\text{C}$ water until their temperatures match. (correct answer)
Net thermal energy flow stops immediately because covering the cup prevents any energy exchange between samples.

Explanation: This question tests understanding of thermal energy transfer and equilibrium. When two samples of the same substance at different temperatures are mixed, thermal energy flows from the higher temperature sample to the lower temperature sample. The 60°C water has more thermal energy per unit mass than the 20°C water, so net thermal energy flows from the warmer to the cooler water until they reach the same equilibrium temperature. Choice C incorrectly suggests that identical substances don't transfer energy, revealing a misconception that material type prevents heat transfer rather than temperature difference driving it. Remember that thermal energy flows from higher to lower temperature until equilibrium, regardless of whether the materials are identical.