First Law of Thermodynamics

Question 1

Question 1: 1. As shown in Figure A is an automobile nitrogen damping device consisting of a cylinder, piston ro...

1. As shown in Figure A is an automobile nitrogen damping device consisting of a cylinder, piston rod, spring and upper and lower supports, a simplified schematic diagram is shown in Figure B. A certain mass of nitrogen (which can be regarded as an ideal gas) is enclosed in the cylinder, and the cylinder has good thermal conductivity and airtightness, and the ambient temperature remains unchanged. Without regard to all friction, the cylinder closed nitrogen gas is slowly compressed in the process, closed nitrogen gas ![](/images/questions/phys-thermodynamics-first-law/image-001.jpg) A ![](/images/questions/phys-thermodynamics-first-law/image-002.jpg) B

A. A. temperature rise
B. B. Increase in internal energy
C. C. do positive work on the outside world
D. D. Heat is released to the outside world

Answer

Answer: D

Solution: B. The cylinder conducts heat well, so the temperature remains constant and the internal energy is unchanged during the slow compression of the closed nitrogen gas in the cylinder, so B is wrong; A. The internal energy of a certain mass of ideal gas is determined by the temperature, combined with the above, the internal energy of the gas is unchanged, then the temperature of the gas is unchanged, so A is wrong; C. The volume of the closed nitrogen gas decreases as it is slowly compressed, and the outside world does work on the closed nitrogen gas, so C is wrong; D. Combined with the above, the internal energy of the closed nitrogen gas is unchanged, and the outside world does work on the gas, according to the first law of thermodynamics. $$ \Delta U = W + Q $$ It can be seen that the closed nitrogen gas releases heat to the outside world, so D is correct.

Question 2

Question 2: 2. One of the following statements is correct

2. One of the following statements is correct

A. A. As the distance between molecules increases, the gravitational force decreases but the repulsive force increases
B. B. The higher the temperature, the higher the average kinetic energy of the molecular thermal motion
C. C. The irregular motion of liquid molecules is called Brownian motion
D. D. The system absorbs heat from the outside world, the internal energy of the system must increase

Answer

Answer: B

Solution: As the distance between the molecules increases, the gravitational force and repulsive force decreases at the same time decreases, so A is wrong; temperature is the molecular thermal movement of the average kinetic energy of the sign, the higher the temperature, the molecular thermal movement of the average kinetic energy of the larger, so B is correct; Brownian motion is suspended in the liquid solid particles of the movement, not the liquid molecules of the irregular movement; so C is wrong; according to the first law of thermodynamics, the system from the outside world to absorb heat may be outside at the same time According to the first law of thermodynamics, the system absorbs heat from the outside world and may do work on the outside at the same time, so the internal energy of the system is not necessarily increased; so D is wrong. Therefore, B.

Question 3

Question 3: 3. As shown in the figure, the bottle is filled with a small amount of water, the mouth of the bottl...

3. As shown in the figure, the bottle is filled with a small amount of water, the mouth of the bottle has been plugged tightly, water vapor in the air above the water, with a pump to the bottle, when the plug from the mouth of the bottle jumped out of the bottle, the bottle appeared to be a "white mist", the phenomenon can be explained in the following three sentences: a, water vapor condensed into small droplets of water; b, the bottle gas to promote the stopper to do work, the internal energy decreases; c, the temperature decreases. Internal energy decreases; C, the temperature decreases. The correct order of the three sentences is ![](/images/questions/phys-thermodynamics-first-law/image-003.jpg)

A. A. A, B, C
B. B. B, C, A
C. C. C, A, B
D. D. B, A, C

Answer

Answer: B

Solution: According to the question of the cause and effect order of the process as : air to push the stopper to do work - the air internal energy decreases - the temperature of the air inside the bottle decreases - the bottle of water vapor liquefied into small droplets of water that is "white mist", and the cork jumped up because of the pump to the bottle so that the gas pressure increases due to. Therefore, the order is B, C, A, B is correct.

Question 4

Question 4: 4. The heat engine on a motorcycle operates to provide power for the stroke ( )

4. The heat engine on a motorcycle operates to provide power for the stroke ( )

A. A. suction stroke
B. B. compression stroke
C. C. the actuating stroke
D. D. exhaust stroke

Answer

Answer: C

Solution: Test Question Analysis: The heat engine on a motorcycle works to provide power during the stroke is a work stroke, so choose C. Points: heat engine In the four-stroke internal combustion engine work stroke, fuel combustion produces a large number of high-temperature and high-pressure gas to push the piston to do work, the internal energy into mechanical energy.

Question 5

Question 5: 5. The following statements about crystals and amorphous bodies are correct ()

5. The following statements about crystals and amorphous bodies are correct ()

A. A. Crystals must be anisotropic in physical properties
B. B. Any solid that does not have a definite melting point must be amorphous
C. C. Substances formed from the same chemical composition can only exist in one crystal structure
D. D. During the melting process, the crystal absorbs heat, but the temperature stays the same and so does the internal energy

Answer

Answer: B

Solution: A. Crystals are divided into single crystals and polycrystals, single crystals are anisotropic in physical properties and polycrystals are isotropic in physical properties, so A is wrong; B. Crystals have a fixed melting point, amorphous body has no fixed melting point, it can be seen, as long as the solid does not have a fixed melting point must be amorphous, so B is correct; C. Substances formed by the same chemical composition may exist in the form of multiple crystal structures at different temperatures, so C is wrong; D. In the melting process, the crystal to absorb heat, but the temperature remains unchanged, that is, the average kinetic energy remains unchanged, due to the absorption of heat, the internal energy increases, so D error.

Question 6

Question 6: 6. The following statements are correct ( )

6. The following statements are correct ( )

A. A. The pressure of a gas is due to the constant and frequent impact of a large number of gas molecules on the walls of the vessel
B. B. If the distance between the molecules is reduced, the molecular gravitational force will decrease and the molecular repulsive force will increase
C. C. If a gas absorbs heat, the internal energy of the gas must increase
D. D. Brownian motion is the irregular motion of molecules

Answer

Answer: A

Solution: A. According to the microscopic explanation of gas pressure, it can be seen that the pressure of a gas is due to the continuous and frequent impact of a large number of gas molecules on the walls of the vessel. Therefore, A is correct; B.If the intermolecular distance is reduced, the molecular gravitational force will increase, and the molecular repulsive force will also increase. Therefore, B is wrong; C. According to the first law of thermodynamics. It can be known that if the gas absorbs heat, the internal energy of the gas does not necessarily increase. Therefore, C error; D. Brownian motion is suspended small particles of irregular motion, indirectly reflecting the irregular motion of molecules. D. Brownian motion is the irregular motion of suspended particles, which indirectly reflects the irregular motion of molecules. D. Brownian motion is the irregular motion of suspended particles, which indirectly reflects the irregular motion of molecules.

Question 7

Question 7: 7. With regard to solids, liquids and gases, the following statements are correct ( ).

7. With regard to solids, liquids and gases, the following statements are correct ( ).

A. A. Crystals must have regular geometric shapes; irregularly shaped metals must be amorphous
B. B. Place a pin lightly on the surface of the water and it will float on the surface due to surface tension on the water surface
C. C. Wooden boats float on water due to surface tension
D. D. When the outside world does work on an object, the internal energy of the object must increase

Answer

Answer: B

Solution: A. Crystals must have regular geometric shapes, and irregularly shaped metals are polycrystals, so A is wrong; B. Put a pin lightly on the water, it will float on the water surface, this is due to the existence of surface tension on the surface of the water, so the B. This is due to the existence of surface tension on the surface of water, so B is correct; C. When a wooden boat floats on the surface of the water, part of the boat has been immersed below the surface of the water, is due to the buoyancy of the water, has nothing to do with the surface tension, so C is wrong; D. According to the first law of thermodynamics $\Delta U = W + Q$, it is known that the work done by the outside world on the object, the internal energy of the object does not necessarily increase, so D is wrong.

Question 8

Question 8: 8. The following statements about internal energy are correct ()

8. The following statements about internal energy are correct ()

A. A. Different objects that have equal temperatures also have equal internal energies
B. B. As the speed of an object increases, the kinetic energy of the molecules increases, and so does their internal energy
C. C. Doing work on an object or transferring heat to an object may change the internal energy of the object
D. D. Ice melts into water at the same temperature, so does the internal energy.

Answer

Answer: C

Solution: A. Internal energy includes molecular kinetic energy and molecular potential energy, and is also related to the amount of matter, A catalyst; B. The average kinetic energy of molecules is related only to temperature, not to the macroscopic motion of objects, B is wrong; C. by the first law of thermodynamics can be done work and heat transfer can change the internal energy of the object, C is correct; D. Ice melts into water, the volume decreases, the molecular potential energy increases, the internal energy increases, D wrong;

Question 9

Question 9: 9. The following statements are correct

9. The following statements are correct

A. A. The volume of a gas is the sum of the volumes of all the gas molecules
B. B. The volume of a gas is difficult to compress, which is a macroscopic manifestation of the existence of repulsive forces between molecules
C. C. The internal energy of an object is the sum of the kinetic energy of the thermal motion of all the molecules that make up the object
D. D. $1 \mathrm {~g} 0 ^ { \circ } \mathrm { C }$ The internal energy of water is greater than the internal energy of $1 \mathrm {~g} 0 ^ { \circ } \mathrm { C }$ ice

Answer

Answer: D

Solution: A. The gaps between the gas molecules are large, so the volume of the gas is much larger than the sum of the volumes of all the gas molecules, so A is wrong; B. The distance between the gas molecules is very large, the molecular force is gravitational, basically zero, and it is difficult to be compressed is the performance of the pressure, so B error; C. The internal energy of the object is composed of all the molecules of the object's kinetic and potential energy of thermal movement of the sum, so C error; D. Ice melting to absorb heat, so the internal energy of $1 \mathrm {~g} 0 ^ { \circ } \mathrm { C }$ of water is greater than that of $1 \mathrm {~g} 0 ^ { \circ } \mathrm { C }$ of ice, so D is correct. D is correct.

Question 10

Question 10: 10. A certain mass of an ideal gas is slowly compressed, and the temperature remains constant during...

10. A certain mass of an ideal gas is slowly compressed, and the temperature remains constant during compression. The following statements are correct)

A. A. The internal energy of the gas remains constant
B. B. The pressure of the gas remains constant
C. C. The average kinetic energy of gas molecules decreases
D. D. No heat exchange between the gas and the outside world

Answer

Answer: A

Solution: AC. If the temperature of an ideal gas remains constant, the internal energy of the gas remains constant and the average kinetic energy of the molecules remains constant, so A is correct and C is wrong; B. Ideal gases undergo isothermal compression process, according to Boyle's law can be seen that the pressure of the gas increases, so B error; D. The gas is compressed process, the outside world on the gas work, and the gas internal energy is unchanged, according to the first law of thermodynamics can be known to the outside world of the gas exothermic, so D error.

Question 11

Question 11: 11. With respect to a certain amount of gas, the following statement is correct

11. With respect to a certain amount of gas, the following statement is correct

A. A. Heat absorbed by a gas can be completely converted into work
B. B. As the volume of a gas increases, its internal energy must decrease
C. C. When a gas absorbs heat from the outside world, its internal energy must increase.
D. D. The work done on the gas by the outside world must increase the internal energy of the gas

Answer

Answer: A

Solution: A. If the gas expands isothermally, the internal energy of the gas remains unchanged and all the heat absorbed is used to do work on the outside, A is correct; B. When the volume of the gas increases, the external work, if at the same time to absorb heat, and the heat absorbed is greater than or equal to the value of the external work, the internal energy will not decrease, B error; C. If the gas absorbs heat and does work on the outside at the same time, its internal energy is not necessarily increased, C error; D. If the outside world on the gas work at the same time the gas to the outside heat, and the heat released more than the outside world on the work done by the gas, the gas internal energy not only did not increase but decreased, D error.

Question 12

Question 12: 12. The following description of the process of energy conversion or transfer is correct.

12. The following description of the process of energy conversion or transfer is correct.

A. A. A car's internal combustion engine does work on the outside by burning gasoline and also dissipates heat into the air, which violates the first law of thermodynamics
B. B. When cold water is poured into a thermos, the temperature of both the cold water and the cup become lower, which is impossible because of the violation of the first law of thermodynamics
C. C. A new type of heat engine works by converting all the heat absorbed from a high-temperature heat source into work without any other effect, which does not violate the first law of thermodynamics, nor the second law of thermodynamics
D. D. The refrigerator's chiller works to realize that heat is emitted from the cooler environment inside the box to the warmer room outside, which violates the second law of thermodynamics.

Answer

Answer: B

Solution: A. The internal energy generated by burning gasoline is converted to mechanical energy on the one hand, while heat transfer to the air at the same time, neither the first law of thermodynamics nor the second law of thermodynamics is violated, option A is wrong; B. Cold water poured into the thermos, no external work, but also no heat transfer, internal energy can not be reduced, so the first law of thermodynamics, option B is correct; C. A new type of heat engine work will be absorbed from a high-temperature heat source of all the heat into work, will inevitably produce other effects so against the second law of thermodynamics, option C is wrong; D. Refrigeration machine consumes electrical energy to work from the box in the low-temperature environment to extract heat emitted to the higher temperature of the room, the transfer of internal energy occurs, and at the same time have an impact on the outside world. Neither the first law of thermodynamics, nor the second law of thermodynamics, option D is wrong.

Question 13

Question 13: 14. When using a rubber-tipped burette, insert it into water, pinch the rubber tip at the end to red...

14. When using a rubber-tipped burette, insert it into water, pinch the rubber tip at the end to reduce its volume, and then expel a certain amount of air and stabilize it as shown in the figure. Then let go, the rubber tip volume increases $V _ { 1 }$, there is a volume of $V ^ { 2 }$ of water into the dropper. Neglecting the change in temperature, the following statement is correct ( ) ![](/images/questions/phys-thermodynamics-first-law/image-004.jpg)

A. A. $V _ { 1 } > V _ { 2 }$
B. B. The gas inside the dropper releases heat to the outside
C. C. The molecules within the surface layer of water are sparser than within the water, so there is only molecular gravity between the molecules within the surface layer
D. D. If you know the volume of gas inside the final dropper and the number of gas molecules you can find the diameter of a gas molecule.

Answer

Answer: A

Solution: A. Let the atmospheric pressure be $p _ { 0 }$ and the density of water be $\rho$, then the pressure of the gas in the beginning $$ p _ { 1 } = p _ { 0 } + \rho g h _ { 1 } $$ Pressure of the gas after inhaling the water $$ p _ { 2 } = p _ { 0 } + \rho g h _ { 2 } $$ Since $h _ { 1 } > h _ { 2 }$, the $$ p _ { 1 } > p _ { 2 } $$ Let the volume of the gas at the beginning be $V _ { 10 }$, the volume of the gas after water is drawn in is $V _ { 20 }$, and the temperature of the gas is constant, according to Boyle's law: $$ p _ { 1 } V _ { 10 } = p _ { 2 } V _ { 20 } $$ Since $$ p _ { 1 } > p _ { 2 } $$ then $$ V _ { 10 } < V _ { 20 } $$ For the rubber-tipped burette $$ V _ { 10 } + V _ { 1 } = V _ { 20 } + V _ { 2 } $$ So $$ V _ { 1 } > V _ { 2 } $$ Therefore, A is correct ; B. The volume of the gas inside the burette becomes larger, and work is done on the outside. Since the temperature remains the same and the internal energy remains the same, the gas absorbs heat, so option B is wrong; C. There are both gravitational and repulsive forces between molecules; the molecular distribution within the surface layer of the liquid is relatively sparse, the combined force of the intermolecular forces for the gravitational force, so C is wrong; D. If you know the final dropper internal gas volume and the number of gas molecules can be found a gas molecules occupy the volume of space, but can not be solved molecular diameter, option D error.

Question 14

Question 14: 15. The following statements are correct ()

15. The following statements are correct ()

A. A. Diffusion can only occur in solids and liquids
B. B. Heat cannot be transferred from a low temperature object to a high temperature object
C. C. Type II perpetual motion machines violate the first law of thermodynamics.
D. D. The small charcoal particles in the ink were observed under a microscope to be in constant irregular motion, which reflects the irregularity of the motion of liquid molecules

Answer

Answer: D

Solution: A. Diffusion can occur between solids, liquids and gases, so A is wrong; B. In the case of other changes, heat can be transferred from low-temperature objects to high-temperature problems, but not spontaneously from low-temperature objects to high-temperature objects, so B error; C.The second type of perpetual motion machine follows the law of conservation of energy, but violates the second law of thermodynamics, so C is wrong; D. The movement of the carbon particles in the ink is due to the imbalance of the impact force of a large number of water molecules on it leading to the movement in all directions, which reflects the irregularity of the movement of liquid molecules, so D is correct.

Question 15

Question 15: 16. A certain mass of closed gas pressure $p$ with the volume $V$ of the law of change as shown in t...

16. A certain mass of closed gas pressure $p$ with the volume $V$ of the law of change as shown in the figure, from the state $A$ to the state $B$ change in the state $B$ of During the process ![](/images/questions/phys-thermodynamics-first-law/image-005.jpg)

A. A. The gas temperature remains constant
B. B. The average force per unit area of the gas on the vessel wall is constant
C. C. External work on the gas
D. D. A gas absorbs heat from the outside world

Answer

Answer: D

Solution: A. During the change from state $A$ to state $B$, the value of $p V$ gradually increases, and according to the ideal gas equation of state $\frac { p V } { T } = C$, the temperature of the gas increases, so A is wrong; B. From state $A$ to state $B$, the gas pressure increases, and the average force per unit area of the gas on the wall of the vessel increases, so B is wrong; C. In the process of changing from state $A$ to state $B$, the volume of the gas increases, and work is done on the outside world, so C is wrong; D. In the process of changing from state $A$ to state $B$, the temperature of the gas rises, the internal energy increases, and work is done on the outside world. According to the first law of thermodynamics, the gas absorbs heat from the outside world, so D is correct.

Question 16

Question 16: 17. As shown in the figure is a closed cylinder, the external force pushes the piston P compresses t...

17. As shown in the figure is a closed cylinder, the external force pushes the piston P compresses the gas, the ideal gas in the cylinder to do work 800 J, while the gas to the outside world exothermic 200 J. The cylinder gas ![](/images/questions/phys-thermodynamics-first-law/image-006.jpg)

A. A. Increase in temperature increases internal energy by 600J
B. B. Increase in temperature decreases internal energy by 200 J
C. C. Temperature decreases, internal energy increases 600 J
D. D. Temperature decreases, internal energy increases by 200J

Answer

Answer: A

Solution: From the first law of thermodynamics $\Delta U = W + Q$ we get $\Delta U = 800 \mathrm {~J} + ( - 200 \mathrm {~J} ) = 600 \mathrm {~J}$ The magnitude of the internal energy of an ideal gas of a given mass depends only on temperature, $\Delta U = 600 \mathrm {~J} > 0$ Therefore, the temperature must increase.

Question 17

Question 17: 18. As shown in the figure, an ideal gas of a certain mass undergoes two processes $a \rightarrow b$...

18. As shown in the figure, an ideal gas of a certain mass undergoes two processes $a \rightarrow b$ and $a \rightarrow c$ respectively, where $a \rightarrow b$ is an isothermal process, and the states $b , c$ are of the same volume, then ![](/images/questions/phys-thermodynamics-first-law/image-007.jpg)

A. A. The internal energy of state $a$ is greater than that of state $b$.
B. B. The temperature of state $a$ is higher than state $c$.
C. C. $a \rightarrow c$ Heat absorbed by the process gas
D. D. If the process varies along $a b c a$ then the outside world does negative work on the gas.

Answer

Answer: C

Solution: A. Since the process of $a \rightarrow b$ is isothermal, i.e. state $a$ and state $b$ have the same temperature and the average kinetic energy of the molecules is the same, the internal energy of state $a$ is equal to the internal energy of state $a$ for an ideal gas. INLINE_FORMULA_6]], so A is wrong; B. Since the states $b$ and $c$ are of the same volume and $p _ { b } < p _ { c }$, according to the ideal gas equation of state, $p _ { b } < p _ { c }$ is the same. $$ \frac { p _ { b } V _ { b } } { T _ { b } } = \frac { p _ { c } V _ { c } } { T _ { c } } $$ B. Because $T _ { b } < T _ { c }$ is the same volume and $T _ { a } = T _ { b }$ is the same volume and $T _ { a } < T _ { c }$ is the same volume, it is wrong; C. Because $a \rightarrow c$ process of gas volume increases, the gas to the outside world to do positive work; and the gas temperature rises, the internal energy increases, according to the $$ \Delta U = W + Q $$ It can be known that the gas absorbs heat; therefore, C is correct. D. If along the $a b c a$ process changes, the gas volume first increased after the decrease, the gas first outside the work done by the outside world, after the outside world on the work done by the gas, from the figure we can see that the outside world on the work done by the gas is greater than the gas to the outside world to do the work, the two stages of the work and that $a b c a$ process enclosed area, we can see that the process of the outside world on the gas to do positive work work, D error. The gas does positive work work, D error.

Question 18

Question 18: 19. An air mass is rising near the ground with negligible heat exchange with the outside world. It i...

19. An air mass is rising near the ground with negligible heat exchange with the outside world. It is known that the atmospheric pressure decreases with height, the air mass in the process of rising (not counting the potential energy between molecules in the air mass)

A. A. Volume decreases, temperature decreases
B. B. Volume decreases, temperature stays the same
C. C. Volume increases, temperature decreases
D. D. Volume decreases, temperature stays the same

Answer

Answer: C

Solution: The pressure decreases during the rise of the gas mass, the gas volume expands, the gas does work to the outside world, the gas has no heat exchange with the outside world, according to the first law of thermodynamics can be known, the internal energy decreases, the ideal gas internal energy is only related to the temperature, so the temperature of the gas is lowered, so ABD is wrong, C is correct.

Question 19

Question 19: 20. The figure shows a simple thermometer designed by a student, a transparent pipette into a contai...

20. The figure shows a simple thermometer designed by a student, a transparent pipette into a container with good thermal conductivity, the connection is sealed, a small column of oil is injected into the pipette, and the external atmospheric pressure remains constant. The container is placed in hot water and a slow rise in the column of oil is observed, the following statements are correct () ![](/images/questions/phys-thermodynamics-first-law/image-008.jpg)

A. A. The work done by the gas on the outside is greater than the heat absorbed
B. B. The work done by the gas on the outside is equal to the heat absorbed
C. C. The average force per unit area on the inner wall of the container by the gas molecules increases
D. D. The average force per unit area on the inner wall of the container by the gas molecules is constant in magnitude

Answer

Answer: D

Solution: AB. According to $\Delta U = Q + W$, the work done by the gas is less than the heat absorbed. The work done by the gas is less than the amount of heat absorbed, so option AB is incorrect; CD.The pressure of the gas remains constant, then the average force per unit area of the inner wall of the container by the gas molecules remains unchanged, option C is wrong, D is correct.

Question 20

Question 20: 21. A certain mass of an ideal gas is kept at a constant pressure of $p$, and the volume of the gas ...

21. A certain mass of an ideal gas is kept at a constant pressure of $p$, and the volume of the gas is measured to be $0 ^ { \circ } \mathrm { C }$ at $V _ { 0 } , 10 ^ { \circ } \mathrm { C }$, and the volume is measured to be $V _ { 1 } , ~ 20 ^ { \circ } \mathrm { C }$, then the following statement is correct ( ). FORMULA_4]], then the following statement is correct ( )

A. A. $V _ { 2 } = V _ { 1 } + \frac { 10 V _ { 0 } } { 273 }$
B. B. $V _ { 2 } = V _ { 0 } + \frac { 10 V _ { 1 } } { 273 }$
C. C. In the process of increasing the temperature of the gas from $0 ^ { \circ } \mathrm { C }$ to $20 ^ { \circ } \mathrm { C }$, the work done by the outside world on the gas is $p \left( V _ { 1 } - V _ { 0 } \right)$
D. D. The number of molecules per unit time impacting a unit area of the container wall increases with increasing temperature

Answer

Answer: A

Solution: AB. An ideal gas of a certain mass keeps the pressure $p$ constant and according to Gay-Lussac's law we have $$ \frac { V _ { 0 } } { T _ { 0 } } = \frac { V _ { 1 } } { T _ { 1 } } = \frac { V _ { 2 } } { T _ { 2 } } $$ According to the relationship between thermodynamic temperature and Celsius temperature, we have $$ T _ { 0 } = 273 \mathrm {~K} , T _ { 1 } = ( 273 + 10 ) \mathrm { K } , T _ { 2 } = ( 273 + 20 ) \mathrm { K } $$ The solution is $$ V _ { 1 } = V _ { 0 } + \frac { 10 V _ { 0 } } { 273 } , V _ { 2 } = V _ { 1 } + \frac { 10 V _ { 1 } } { 283 } = V _ { 1 } + \frac { 10 V _ { 0 } } { 273 } = V _ { 0 } + \frac { 20 V _ { 1 } } { 283 } $$ Therefore, A is correct and B is wrong; C. The temperature of the gas increases from $0 ^ { \circ } \mathrm { C }$ to $20 ^ { \circ } \mathrm { C }$, the pressure of the gas stays the same, the volume increases, and the work done by the gas on the outside is $$ W = p \left( V _ { 2 } - V _ { 0 } \right) $$ Therefore, C is wrong; D. gas temperature increases, the average kinetic energy of the molecules increase, the volume of gas increases, the pressure remains unchanged, according to the pressure microscopic significance of the gas molecules per unit of time on the wall of the number of collisions per unit area of the wall is reduced, so D error.

Question 21

Question 21: 22. The following statements are false ( )

22. The following statements are false ( )

A. A. Many of the droplets in the splash caused by the athlete's entry into the water appear spherical because of the surface tension of the water.
B. B. In the absence of heat exchange with the outside world, compression of a certain mass of ideal gas, the gas temperature must rise
C. C. A solid with a fixed melting point must be a crystal
D. D. The wooden block floats on the water surface because of the surface tension of the liquid

Answer

Answer: D

Solution: A. In the splash of water stirred up by the athlete's entry process, many water droplets show a spherical shape under the action of surface tension, so A is correct and does not meet the meaning of the question; B. In the absence of heat exchange with the outside world under the conditions of compression of a certain mass of ideal gas, the outside world on the work done by the gas, according to heat B. In the absence of heat exchange with the outside world, the compression of a certain mass of ideal gas, the outside world on the gas work, according to the first law of thermodynamics can be known that the internal energy must increase, then the gas temperature must rise, so B is correct, does not accord with the meaning; C. crystals have a certain melting point, non-crystalline does not have a certain melting point, then a fixed melting point of the solid must be crystals, so C is correct, does not meet the meaning of the question; D. The wooden block floats on the water surface because the block is subject to the balance of buoyancy and gravity, not the role of the surface tension of the liquid, so D is wrong, in line with the meaning of the question.

Question 22

Question 22: 23. With respect to the laws of thermodynamics, the following statements are correct

23. With respect to the laws of thermodynamics, the following statements are correct

A. A. The temperature of an object can drop to 0 K under certain conditions.
B. B. An object cannot absorb heat from a single heat source and use it all for work without other effects
C. C. An object that has absorbed heat must have increased its internal energy
D. D. Compressing a gas always raises the temperature of the gas

Answer

Answer: B

Solution: A.Absolute zero can only be approached indefinitely and can never be reached, so A is wrong; B.It is impossible for an object to absorb heat from a single heat source and use it all for work without other effects, so B is correct; C. By the first law of thermodynamics, the change of internal energy is determined by the work and heat transfer, so the object absorbed heat, its internal energy is not necessarily increased. Compressing a gas does not necessarily increase the temperature of the gas, so CD is wrong.

Question 23

Question 23: 24. As shown in the figure, the cylindrical cylinder inside the piston closed with a certain amount ...

24. As shown in the figure, the cylindrical cylinder inside the piston closed with a certain amount of ideal gas, the initial state, the cylinder column length of ${ } ^ { L _ { 1 } }$, the temperature of ${ } ^ { T _ { 1 } }$, now the gas will be heated, the length of the column of gas from the ${ } ^ { L _ { 1 } }$ slowly change to [[[]]], the gas absorbs heat 360J, the piston does work of 100 J, the following statements are correct for the above change process. INLINE_FORMULA_3]], the gas absorbs 360 J of heat and does 100 J of work on the piston, and the following statements are correct about the above change. ![](/images/questions/phys-thermodynamics-first-law/image-009.jpg)

A. A. The pressure of the gas is increasing
B. B. The internal energy of the gas increases by 460J
C. C. The gas may return to its original state after giving off 200 J of heat.
D. D. The gas may return to its original state after giving off 300 J of heat.

Answer

Answer: D

Solution: A. Analyze the force on the piston, according to the equilibrium conditions, the pressure of the gas is unchanged, so A is wrong; B. According to the first law of thermodynamics $\Delta U = W + Q$, where $Q = 360 \mathrm {~J} , W = - 100 \mathrm {~J}$, solve for $$ \Delta U = 260 \mathrm {~J} $$ Therefore, the internal energy of the gas increases by 260J, so B is wrong; CD. If the gas to restore the initial state, then the internal energy needs to be reduced by 260 J, the process of volume reduction, the outside world on the gas to do work, according to the first law of thermodynamics, so the gas must be more than 260 J of heat released, so C is wrong, D is correct.

Question 24

Question 24: 25. One of the following statements about heat is correct

25. One of the following statements about heat is correct

A. A. All natural processes always proceed in the direction of decreasing disorder in the thermal motion of molecules
B. B. When an ideal gas is compressed under adiabatic conditions, the internal energy of the gas must increase
C. C. Brownian motion is the irregular movement of liquid molecules seen in a microscope
D. D. The greater the difference between the actual pressure of water vapor in air and the saturated vapor pressure at the same temperature, the more unfavorable it is for evaporation

Answer

Answer: B

Solution: A. All natural processes are always in the direction of molecular thermal motion of the increasing disorder, so A error; B. compression of an ideal gas under adiabatic conditions, the outside world on the gas to do positive work, according to the first law of thermodynamics can be known, the internal energy of the gas must increase, so B is correct; C. Brownian motion is the irregular motion of solid particles seen in the microscope, so C is wrong; D. The actual pressure of water vapor in the air and the same temperature saturation vapor pressure difference is greater, the more conducive to evaporation, so D error; Therefore, choose B.

Question 25

Question 25: 26. The following statements are correct

26. The following statements are correct

A. A. Objects with different internal energies cannot have the same average kinetic energy of their molecular thermal motion
B. B. The temperature of an ideal gas of a certain mass must decrease during isobaric expansion
C. C. For a given mass of gas, the average number of collisions of molecules per second with the walls of the vessel decreases with decreasing temperature at constant volume
D. D. When the outside world does work on a gas, its internal energy must increase

Answer

Answer: C

Solution: A. Because objects with different internal energies may have the same temperature, the average kinetic energy of molecular thermal motion may be the same, so A is wrong; B. By the ideal gas equation of state $$ \frac { p V } { T } = C $$ B. By the ideal gas equation of state $$ \frac { p V } { T } = C $$, the temperature of isobaric expansion must increase, so B is wrong; C. A certain mass of gas, in the volume of the same, the number of molecules in the density of the same, the temperature decreases, the pressure decreases, so that the average number of molecular collisions per second is also reduced, so C is correct; D. According to the first law of thermodynamics, the outside world on the gas work, if at the same time outward heat, then its internal energy is not necessarily increased, so D error.

Question 26

Question 26: 27. As shown in the figure is nowadays popular "self-heating rice", the bottom layer has a heating p...

27. As shown in the figure is nowadays popular "self-heating rice", the bottom layer has a heating package, add water, the rice layer cover, in the bottom layer will be sealed part of the gas, the heating package in the material and the reaction of water to release a large amount of heat, after a period of time that is heated up the rice. Bottom The gas in the layer can be regarded as an ideal gas, ignoring the volume change of the lunch box in the heating process, the following statements are correct ( ) ![](/images/questions/phys-thermodynamics-first-law/image-010.jpg)

A. A. The average kinetic energy of the underlying gas molecules increases after heating
B. B. The rate of motion of all gas molecules in the bottom layer increases after heating
C. C. The bottom gas does work on the meal after heating and the internal energy of the gas does not change
D. D. The pressure of the bottom gas remains constant after heating

Answer

Answer: A

Solution: AB . After heating, the temperature increases and the average kinetic energy of the gas molecules increases, but not every gas molecule in the box increases in rate, so A is correct and B is wrong; CD. the bottom of the gas can be regarded as an ideal gas, the temperature increases, the bottom of the internal energy of the gas increases, according to the ideal gas equation of state $$ \frac { p V } { T } = C $$ According to the ideal gas equation of state $$ \frac { p V } { T } = C $$, the heating process is regarded as an isovolumetric change in the work done is zero, then after heating the bottom gas pressure becomes larger, so CD error. Therefore, CD is wrong.

Question 27

Question 27: 28 . The following statements are true about solids, liquids, gases and changes of state ( )

28 . The following statements are true about solids, liquids, gases and changes of state ( )

A. A. Crystals must be characterized by anisotropy
B. B. Liquid surface tension is the interaction between molecules within a liquid
C. C. $0 ^ { \circ } \mathrm { C }$ for iron and $0 ^ { \circ } \mathrm { C }$ for copper, which have the same average molecular rate
D. D. An ideal gas of a certain mass does not necessarily change its internal energy when its state changes

Answer

Answer: D

Solution: A. Single crystals are characterized by anisotropy, while polycrystals exhibit isotropy, option A is wrong; B.Liquid surface tension is the interaction between molecules in the surface layer of a liquid, option B is wrong; C. Iron in $0 ^ { \circ } \mathrm { C }$ and copper in $0 ^ { \circ } \mathrm { C }$ have the same average kinetic energy of the molecules, but the average molecular rate is not the same; D. When the state of an ideal gas of a certain mass is changed, its internal energy remains unchanged if the temperature remains unchanged, so D is correct;

Question 28

Question 28: 29. Summer, if the bicycle inner tube is over-inflated, and placed in the sun, the tire is very easy...

29. Summer, if the bicycle inner tube is over-inflated, and placed in the sun, the tire is very easy to burst, about this phenomenon there are the following description (the inner tube in the process of exposure to the sun is almost unchanged), the error is ( )

A. A. Tire blowout, is the result of the temperature of the gas inside the tire rises, the repulsive force between the gas molecules increases dramatically
B. B. In the process before the burst of gas temperature increases, the molecular irregular thermal movement increases, the gas pressure increases
C. C. In the process leading up to the burst, the gas absorbs heat and increases its internal energy
D. D. At the moment of a sudden tire burst, the internal energy of the gas decreases

Answer

Answer: A

Solution: spacing between gas molecules, gas molecules between the molecular force (repulsion) is negligible, so A meets the meaning of the question; bicycle burst before the process of exposure to the sun, the gas inside the tire heat-absorbing temperature increases, the average kinetic energy of the molecules increased, while the volume of gas is unchanged, the number of molecules per unit of volume remains unchanged, so the gas pressure increases, so B does not meet the meaning of the question; according to the first law of thermodynamics, the gas before the burst of the internal energy should be increased, therefore C is not consistent with the meaning of the question; sudden burst of gas to the outside world to do work at the moment, its internal energy should be reduced, so D is not consistent with the meaning of the question.

Question 29

Question 29: 30. A reciprocating internal combustion engine operates using the Diesel cycle, which consists of tw...

30. A reciprocating internal combustion engine operates using the Diesel cycle, which consists of two adiabatic processes, an isobaric process and an isovolumic process. The diagram shows a Diesel cycle experienced by a certain mass of an ideal gas, which ( ) ![](/images/questions/phys-thermodynamics-first-law/image-011.jpg)

A. A. The internal energies in states c and d may be equal.
B. B. During $\mathrm { a } \rightarrow \mathrm { b }$, all of the work done on it by the outside world is used to increase internal energy
C. C. $\mathrm { a } \rightarrow \mathrm { c }$ process increases internal energy less than $\mathrm { c } \rightarrow \mathrm { d }$ process decreases internal energy
D. D. The amount of heat absorbed during a cycle is less than the amount of heat given off

Answer

Answer: B

Question 30

Question 30: 31. As shown in the figure, a valve $\mathrm { P } , \mathrm { Q }$ between two connected containers...

31. As shown in the figure, a valve $\mathrm { P } , \mathrm { Q }$ between two connected containers $\mathrm { K } , \mathrm { P }$ is filled with gas, Q is a vacuum, and there is no heat exchange between the whole system and the outside world. When valve K is opened, the gas in P enters Q and equilibrium is finally reached, then ( ) ![](/images/questions/phys-thermodynamics-first-law/image-012.jpg)

A. A. The gas expands in volume and the internal energy decreases
B. B. The potential energy of the gas molecules decreases and the internal energy increases
C. C. The kinetic energy of the gas molecules increases and the internal energy remains constant
D. D. It is not possible for the gas in Q to spontaneously return all the way back into $P$

Answer

Answer: D

Solution: ABC. After opening the valve K, the gas in P enters into Q. Since there is a vacuum in Q, there is no external work done when the volume of the gas increases, and the potential energy of the molecules remains unchanged, and since there is no heat exchange in the system, the internal energy remains unchanged and the temperature remains unchanged, the kinetic energy of the gas molecules remains unchanged, and the option ABC is wrong; D. By the second law of thermodynamics can be known, nature involves thermal phenomena in the macroscopic process have direction, then Q in the gas does not D. By the second law of thermodynamics, all macroscopic processes involving thermal phenomena in nature are directional, so the gas in Q cannot spontaneously return to P. Option D is correct.

Question 31

Question 31: 32. The following statements about thermal phenomena are correct

32. The following statements about thermal phenomena are correct

A. A. The phenomenon of diffusion indicates the existence of repulsive forces between molecules
B. B. An ideal gas of a certain mass does work on the outside, the internal energy does not necessarily decrease
C. C. A given mass of $0 ^ { \circ } \mathrm { C }$ ice melts into $0 ^ { \circ } \mathrm { C }$ water with no change in its internal energy
D. D. Brownian motion is the irregular movement of pollen particle molecules

Answer

Answer: B

Solution: A. Diffusion is a macroscopic manifestation of irregular molecular motion, and has nothing to do with intermolecular forces; B. According to the first law of thermodynamics $\Delta U = Q + W$ B. According to the first law of thermodynamics $\Delta U = Q + W$, if a gas does work on the outside but absorbs heat, $W$ is negative, $Q$ is positive, and the internal energy may be unchanged or increased, $B$ is correct; C. Ice melts into water and absorbs heat, the potential energy of the molecules increases, and the internal energy increases, C is wrong; D. Brownian motion is the pollen particles by the liquid molecules impact produced by the movement, reflecting the liquid molecules irregular movement, D error. Therefore, choose B.

Question 32

Question 32: 33. The following narratives are correct

33. The following narratives are correct

A. A. Macroscopic processes involving thermal phenomena carried out in nature are directional in nature
B. B. The greater the pressure of the gas, the greater the average kinetic energy of the gas molecules
C. C. During the adiabatic process, work is done on the gas, and the internal energy of the gas must decrease.
D. D. As the temperature increases, the rate of thermal motion of every molecule in the object increases

Answer

Answer: A

Solution: A. According to the second law of thermodynamics, macroscopic processes involving thermal phenomena carried out in nature are directional, option A is correct; B. The greater the pressure of a gas, the higher the temperature, so the average kinetic energy of the gas molecules is not necessarily greater, option B is wrong; C. In the adiabatic process of the outside world on the gas work, according to $\Delta U = W + Q$ get the internal energy of the gas is bound to increase, option C is wrong; D. Temperature increases, the average kinetic energy of molecules increases, but the rate of thermal motion of individual molecules does not necessarily increase, option D is wrong.

Question 33

Question 33: 34. The four-stroke internal combustion engine of an automobile operates using the Otto cycle, which...

34. The four-stroke internal combustion engine of an automobile operates using the Otto cycle, which can be regarded as consisting of two adiabatic processes and two isovolumic processes as shown in the figure for a certain mass of an ideal gas undergoes the Otto cycle, then the gas ![](/images/questions/phys-thermodynamics-first-law/image-013.jpg)

A. A. During $a \rightarrow b$, all the work done on it by the outside world is used to increase its internal energy
B. B. The average kinetic energy of gas molecules may be equal in states $a$ and $c$.
C. C. During $\mathrm { b } \rightarrow c$, the gas temperature remains constant
D. D. The heat absorbed by the gas during a cycle is less than the heat given off

Answer

Answer: A

Solution: A. $a \rightarrow b$ process is an adiabatic compression process, the outside world is doing positive work on it, and there is no heat exchange with the outside world, according to the first law of thermodynamics, all the work done by the outside world is used to increase the internal energy, so A is correct; A is correct. From the analysis of A, the temperature of state $b$ is higher than that of $a$, and the process of $b$ to $c$ is isovolumetric, and the pressure increases, and the temperature increases, so the $c$ is isovolumetric, and the pressure increases, and the temperature increases. INLINE_FORMULA_5]] is greater than $a$, so the average kinetic energies of the gas molecules cannot be equal, so BC is wrong; D. In the process of $\mathrm { b } \rightarrow c$, the gas absorbs heat from the $c \rightarrow d$ which is an adiabatic process, and the gas does work on the outside from the $d \rightarrow a$ which is an isothermal process. From $d \rightarrow a$ to $d \rightarrow a$ is an isovolumic process, the temperature decreases, the gas exothermic, in a cycle process, the gas internal energy change is zero, and the area in the image of $a b c d$ is the external work of the gas, so the gas absorbed heat is greater than that given out, so D is wrong.

Question 34

Question 34: 35. Experienced farmers often judge the water quality in the pond by the bubbles in the pond. Set un...

35. Experienced farmers often judge the water quality in the pond by the bubbles in the pond. Set underwater bubble air (can be regarded as an ideal gas) pressure is equal to the pressure of the water outside the bubble surface, when the temperature of the water up and down the same and remain unchanged, the bubble slowly rise in the process of the following statement is correct

A. A. The bubble does work on the outside world and the bubble absorbs heat from the outside world.
B. B. The outside world does work on the bubbles, and the bubbles release heat to the outside.
C. C. Bubbles do work on the outside, bubbles release heat to the outside
D. D. The outside world does work on the bubble and the bubble absorbs heat from the outside world.

Answer

Answer: A

Solution: During the rise of the bubble, the pressure inside the bubble decreases and the temperature remains constant, according to $p _ { 1 } V _ { 1 } = p _ { 2 } V _ { 2 }$. volume becomes larger, then the gas does work on the outside world, and according to the first law of thermodynamics $\Delta U = Q + W$, since the temperature remains the same, the $\Delta U = 0$ where ${ } ^ { W < 0 }$, so $$ Q > 0 $$ The bubble absorbs heat from the outside world.

Question 35

Question 35: 36. As shown in the figure, a metal cylinder with good thermal conductivity is enclosed in a certain...

36. As shown in the figure, a metal cylinder with good thermal conductivity is enclosed in a certain mass of ideal gas. Now slowly pour a certain mass of sand to the piston, ignoring the change in ambient temperature, in the process of ![](/images/questions/phys-thermodynamics-first-law/image-014.jpg) ![](/images/questions/phys-thermodynamics-first-law/image-015.jpg)

A. A. The average kinetic energy of a large number of molecules in the cylinder increases
B. B. The internal energy of the gas increases
C. C. Increase in the number of molecules per unit time hitting a unit area of the cylinder wall
D. D. The average force of a large number of molecules in the cylinder hitting the cylinder wall increases

Answer

Answer: C

Solution: AB. due to good thermal conductivity of the metal cylinder, and slowly to the piston on the pouring of sand, due to the ambient temperature is unchanged, the temperature of the cylinder gas is unchanged, so the average kinetic energy of the molecules is unchanged, the gas is unchanged, the internal energy, so the AB error; C. isothermal compression, according to the Boyle's law that the pressure increases, the number of molecules per unit of time to hit the cylinder wall per unit of area increases, so the C is correct; D. As the ambient temperature is unchanged, the average kinetic energy of the gas molecules is unchanged, the average rate of molecules did not change, so a large number of molecules in the cylinder impact on the cylinder wall of the average force did not change, so D error.

Question 36

Question 36: 37. a certain mass of ideal gas, starting from state A, through (1) (2) two different processes to r...

37. a certain mass of ideal gas, starting from state A, through (1) (2) two different processes to reach state C, $p - \mathrm { T }$ image shown in the figure, the following statement is correct ![](/images/questions/phys-thermodynamics-first-law/image-016.jpg)

A. A. Process (1) Gas does work on the outside
B. B. Process (2) the gas gives off heat before absorbing it
C. C. The heat absorbed by the gas in process (1) is less than the heat absorbed in process (2)
D. D. State A has more molecular collisions per unit time than state C per unit area of the wall.

Answer

Answer: C

Solution: AD. process (1) gas pressure and thermodynamic temperature is proportional to the gas isovolumetric changes, the volume of the gas is unchanged, the outside world on the gas does not do work, the gas temperature rises, the internal energy increases, by the first law of thermodynamics $$ \Delta U = Q + W $$ It can be seen, the gas absorbs heat, unit time, state A than state C, the number of molecular collisions per unit area of the wall is less, so AD error; B. AB process gas pressure is unchanged, the temperature rises, by the cover a Lussac's law can be known by its volume increases, the gas to the outside world to do work, the gas temperature increases, the internal energy increases, by the first law of thermodynamics $$ \Delta U = Q + W $$ It can be seen that the gas to absorb heat, and the work done by the gas to the outside world is less than the heat absorbed by the gas, BC process of isothermal changes in the gas, the internal energy of the gas remains unchanged, the pressure increases, by Boyle's law can be seen, the volume decreases, the outside world to the gas work, by the first law of thermodynamics $$ \Delta U = Q + W $$ It can be known that the gas exothermic, and the work done by the outside world on the gas is equal to the heat released by the gas, then the process (2) the gas first absorbed heat after the release of heat, so B error; C. The heat absorbed by the gas in process (1) is $$ Q _ { 1 } = \Delta U $$ The amount of heat absorbed by the gas in process (2) is $$ Q _ { 2 } = \Delta U + W $$ The amount of heat absorbed by the gas in process (1) is less than the amount of heat absorbed in process (2), so C is correct.

Question 37

Question 37: 38 . The following statements are correct ()

38 . The following statements are correct ()

A. A. Molecules in a crystal remain immobile in their respective equilibrium positions
B. B. All molecules in $- 260 ^ { \circ } \mathrm { C }$ nitrogen have a small rate of thermal motion
C. C. When a gas in a closed container expands adiabatically, the internal energy increases
D. D. When a gas in a closed container is compressed adiabatically, the pressure increases

Answer

Answer: D

Solution: A. The molecules in the crystal vibrate near the equilibrium position, not remain motionless, so A is wrong; B.When $260 ^ { \circ } \mathrm { C }$ is - $260 ^ { \circ } \mathrm { C }$, there are also molecules in the nitrogen gas with a large rate, but the proportion is small, so B is wrong; C. According to the first law of thermodynamics $\Delta U = Q + W$, the gas expands adiabatically and does work to the outside world, i.e. $Q = 0 , W < 0$, and $\Delta U < 0$, i.e., the internal energy decreases, so C is wrong; D. closed container of gas in the adiabatic compression, the gas volume decreases, the outside world on the gas work, the gas internal energy increases, the temperature rises, according to the ideal gas equation of state can be known, the gas pressure becomes larger, so D is correct.

Question 38

Question 38: 39. The relationship between the volume $V$ and the temperature $t$ of a certain mass of an ideal ga...

39. The relationship between the volume $V$ and the temperature $t$ of a certain mass of an ideal gas is shown in the figure, and the ideal gas undergoes the process of $A \rightarrow B \rightarrow C \rightarrow D \rightarrow A$ from the state A, where the $C D$ segment is parallel to the $t$ axis, and the extension of $D A$ crosses the origin $D A$. INLINE_FORMULA_4]] axis, the extension of $D A$ passes through the origin $O , A B$, and the inverse extension of $O , A B$ intersects with the $t$ axis with the coordinates $( - 273.150 )$. Then ( ) ![](/images/questions/phys-thermodynamics-first-law/image-017.jpg)

A. A. The pressure of the gas increases during $A \rightarrow B$.
B. B. The pressure of the gas remains constant during $D \rightarrow A$.
C. C. A gas emits heat to the outside world during $D \rightarrow A$, and its internal energy decreases
D. D. A gas absorbs heat from the outside world during $B \rightarrow C$ and increases its internal energy

Answer

Answer: C

Solution: A. Since $A \rightarrow B$ of the $V - t$ image of the inverse extension of the line and the axis of the intersection of the coordinates of $( - 273.15 )$ ), can be known that the gas from the state A to the state B is an isobaric change. Therefore, A is wrong; B. According to B. According to $$ \frac { p V } { 273.15 + t } = C $$ Combined with the extension line of $D A$ across the origin $O$, we can see that the pressure becomes stronger. Therefore, $B$ is wrong; C. gas in the $D \rightarrow A$ process, the temperature decreases, the internal energy decreases, the volume decreases, the outside world on the gas work, by the first law of thermodynamics can be known, the gas to the outside world to release heat. Therefore, C is correct; D. From the figure can be seen, the gas from state B to state C, the temperature remains unchanged, the volume becomes larger, it can be seen, the internal energy of the gas remains unchanged, the gas external work, by the first law of thermodynamics can be seen, the gas in the $B \rightarrow C$ process from the outside world to absorb heat. Therefore, $D$ is wrong.

Question 39

Question 39: 40. As shown in the figure, an ideal gas of a certain mass passes from state $A$ through states $B$,...

40. As shown in the figure, an ideal gas of a certain mass passes from state $A$ through states $B$, $C$, and $D$ and then returns to state A. In this case, $A \rightarrow B$ and $C \rightarrow D$ are isothermal processes. Among them, $A \rightarrow B$ and $C \rightarrow D$ are isothermal processes, and $B \rightarrow C$ and $D \rightarrow A$ are adiabatic processes (no exchange of heat between the gas and the outside). This is the famous "Carnot cycle", the following statements are correct ( ) ![](/images/questions/phys-thermodynamics-first-law/image-018.jpg) High School Physics Assignments, October 30, 2025

A. A. $A \rightarrow B$ process, the gas absorbs heat from the outside world and uses it all to do work on the outside world, so the second law of thermodynamics is violated B. $B \rightarrow C$ process, the average kinetic energy of the gas molecules decreases
B. B. As shown in the figure, an ideal gas of a certain mass passes from state $A$ through states $B$, $C$, and $D$ and then returns to state A. In this case, $A \rightarrow B$ and $C \rightarrow D$ are isothermal processes. Among them, $A \rightarrow B$ and $C \rightarrow D$ are isothermal processes, $B \rightarrow C$ and $D \rightarrow A$ are isothermal processes, $D \rightarrow A$ and $C \rightarrow D$ are isothermal processes, and $C \rightarrow D$ is isothermal processes.
C. C. $C \rightarrow D$ process decreases the number of molecules per unit time that collide with the wall per unit area of the apparatus
D. D. $D \rightarrow A$ process, the rate distribution curve of the gas molecules does not change

Answer

Answer: B

Solution: A. $A \rightarrow B$ process, the temperature is unchanged internal energy is unchanged, so the gas from the outside world to absorb heat and all used to do work outside, the process must have the role of the outside world, and therefore produced other effects, does not violate the second law of thermodynamics, A error; B. $B \rightarrow C$ for the adiabatic process, the volume increases external work, by the first law of thermodynamics can be known, the internal energy decreases the temperature decreases, so the average kinetic energy of the gas molecules decreases, B correct; C. $C \rightarrow D$ process, the temperature is unchanged, the volume decreases the pressure increases, from a microscopic point of view, the number of molecules per unit time collision per unit area of the wall of the increase, C error; D. $D \rightarrow A$ for the adiabatic process, the volume decreases, the outside world on the gas work, so the internal energy increases, the temperature increases, the average kinetic energy of the molecules increases, the rate distribution curve of the gas molecules will change, D error.

First Law of Thermodynamics

Topic Overview

Key Points

Study Tips

Practicing topics ≠ Passing the exam

Related Learning Resources