Kinetic Theory of Gases

Question 1

Question 1: 1. Brownian motion was discovered in 1826 by the English botanist Brown when he used a microscope to...

1. Brownian motion was discovered in 1826 by the English botanist Brown when he used a microscope to observe pollen suspended in water. Brownian motion can be observed not only for pollen and small charcoal particles, but also for different suspended particles in liquids, such as colloids. For Brownian motion, the following statements are correct ( )

A. A. Brownian motion is the motion of molecules
B. B. Brownian motion shows that there are only repulsive forces between molecules
C. C. The higher the temperature, the more pronounced the Brownian motion
D. D. The larger the particle suspended in the liquid, and the more liquid molecules that hit the particle at the same instant, the more pronounced the Brownian motion is

Answer

Answer: C

Solution: A. Brownian motion refers to the irregular motion of particles suspended in a liquid, not the molecules themselves, just reflecting the irregular motion of molecules, A error; B. Brownian motion phenomenon is the irregular motion of suspended particles, it shows that the liquid molecules never stop doing irregular motion, B error ; C. The higher the temperature of the liquid, the more intense the movement of liquid molecules, Brownian motion is due to the impact of liquid molecules formed, the more significant Brownian motion, C is correct; D. Suspended in the liquid or gas particles in the smaller, liquid molecules or gas molecules on the particles caused by the impact of the imbalance of the more obvious, the more obvious Brownian motion, D error.

Question 2

Question 2: 2. There are both gravitational and repulsive forces between molecules, the following statements are...

2. There are both gravitational and repulsive forces between molecules, the following statements are correct ( )

A. A. Gravitational forces between solid molecules are always greater than repulsive forces
B. B. A gas can fill any apparatus because the repulsive force between molecules is greater than the gravitational force
C. C. The gravitational force between molecules increases as the distance between them increases, while the repulsive force decreases as the distance increases
D. D. Both gravitational and repulsive forces between molecules decrease as the distance between molecules increases

Answer

Answer: D

Solution: The gravitational force between molecules of a solid is always equal to the repulsive force, otherwise the volume of the solid should be reduced, so A is wrong; the gas can fill any instrument because the molecules are in a never-ending irregular motion, so B is wrong; there are interactions between the molecules of the gravitational force and repulsive force, the gravitational force and repulsive force with the distance between the molecules decreases and increases, with the molecular distance increases and decreases, so C is wrong, D is correct. Therefore, D is correct and ABC is wrong.

Question 3

Question 3: 3. The following statements about the characteristics of the thermal motion of gas molecules are cor...

3. The following statements about the characteristics of the thermal motion of gas molecules are correct ( )

A. A. Gas molecules are more widely spaced, so they don't collide as often
B. B. The average rate of gas molecules increases with increasing temperature
C. C. The rate of motion of gas molecules can be found from Newton's laws of motion
D. D. When the temperature increases, the rates of gas molecules will deviate from the normal distribution

Answer

Answer: B

Solution: A. Because never stop doing irregular motion, so the molecules can not avoid each other collision. B. Temperature is the average kinetic energy of molecules, the average rate of gas molecular movement is related to the temperature, the average rate of gas molecules with the increase in temperature and increase, so B is correct; C. Newton's laws of motion are macroscopic laws, which cannot be used to find the rate of motion of microscopic molecules. C. Newton's laws of motion are macroscopic laws and cannot be used to find the rate of microscopic molecular motion; D. The rate distribution of gas molecules is "more in the middle and less at both ends", which has nothing to do with whether the temperature increases. Therefore, D is wrong.

Question 4

Question 4: 4. The following statements are true about Brownian motion

4. The following statements are true about Brownian motion

A. A. The larger the volume of small solid particles, the more pronounced the Brownian motion is
B. B. The greater the number of liquid molecules that collide with a small solid particle, the more significant the Brownian motion is
C. C. The irregularity of Brownian motion, which mirrors the irregularity of molecular motion in liquids
D. D. Brownian motion is the irregular motion of liquid molecules

Answer

Answer: C

Solution: Brownian motion is suspended in the liquid solid particles of the irregular movement, because the liquid molecules in the process of irregular movement of the impact of solid particles in the imbalance caused by the liquid molecules, so it can reflect the irregular movement of liquid molecules, can not be said to be the liquid molecules of the irregular movement; the smaller the solid particles, at the same time that the number of molecules that impact the solid particles is the smaller the number of the imbalance will be the more pronounced, the Brownian motion will be more pronounced, so the C is correct, ABD is wrong.

Question 5

Question 5: 5. As shown in the figure, a fixed cylinder $A$ and $B$ each contain a certain mass of an ideal gas ...

5. As shown in the figure, a fixed cylinder $A$ and $B$ each contain a certain mass of an ideal gas enclosed by pistons whose areas are proportional to $S _ { A } : \mathrm { S } _ { \mathrm { B } } = 1 : 2$. The two pistons are connected by a rigid rod passing through the bottom of $B$ and can slide horizontally without friction. Neither cylinder leaks. When the system is in equilibrium, the pressure of the gas in $A$ is $\mathrm { p } _ { \mathrm { A } } = 1.5 p _ { 0 } , p _ { 0 }$ is the atmospheric pressure outside the cylinders, so the pressure of the gas in $B$ at this time is ![](/images/questions/phys-kinetic-theory/image-001.jpg)

A. A. $0.75 p _ { 0 }$
B. B. $0.25 p _ { 0 }$
C. C. $0.5 p _ { 0 }$
D. D. $p _ { 0 }$

Answer

Answer: A

Solution: For gases in $A$, there are $$ p _ { A } S _ { A } = F + p _ { 0 } S _ { A } $$ For the gas in $B$, there is a [BLOCK_FORMULA_0]]. $$ p _ { B } S _ { B } + F = p _ { 0 } S _ { B } $$ The association, can be obtained $$ p _ { B } = 0.75 p _ { 0 } $$

Question 6

Question 6: 6. A certain mass of ideal gas from the state $a$, through the $a b , b c , c a$ three processes, th...

6. A certain mass of ideal gas from the state $a$, through the $a b , b c , c a$ three processes, the $V - T$ image shown in the figure, the following statements are correct ( ) ![](/images/questions/phys-kinetic-theory/image-002.jpg)

A. A. The pressure in the $a$ state is less than the pressure in the $b$ state.
B. B. The pressure in the $b$ state is greater than the pressure in the $c$ state.
C. C. $c$ The average kinetic energy of the state molecule is greater than the average kinetic energy of the $a$ state molecule
D. D. The kinetic energy of each molecule in the $c$ state is greater than that in the $a$ state

Answer

Answer: C

Solution: A. The $V - T$ image of $a$ to $b$ is an isothermal change by Boyle's law $$ p V = C $$ By Boyle's law $$ p V = C $$, the pressure in the $a$ state is greater than that in the $b$ state, so A is wrong; B. From the image, $b$ to $c$, the volume is unchanged. $$ \frac { p } { T } = C $$ By Charlie's law $$ \frac { p } { T } = C $$, the pressure in the $b$ state is less than that in the $c$ state, which is wrong; C. From the diagram, the temperature of the $c$ state is greater than that of the $a$ state, so the average kinetic energy of the molecules in the $c$ state is greater than that of the molecules in the $a$ state, C is correct; D. The average kinetic energy of the molecules in the $c$ state is greater than the average kinetic energy of the molecules in the $a$ state, but not every molecule has a greater kinetic energy $c$ than that in the $a$ state, D. Correct. D is incorrect.

Question 7

Question 7: 7. A drop of ink is placed in a glass of water to make a suspension for observation under a microsco...

7. A drop of ink is placed in a glass of water to make a suspension for observation under a microscope. If tracking the movement of a small charcoal particles, every 30 s to observe the position of the charcoal particles recorded, and then connect these positions with a straight line in turn, you get the folding line shown in the figure. Then the following judgment is correct ( ) ![](/images/questions/phys-kinetic-theory/image-003.jpg)

A. A. The folded line in the figure shows the trajectory of the small charcoal particle movement
B. B. The motion of the small charcoal particles can be seen to be irregular
C. C. Recorded as the irregular motion of carbon molecules
D. D. It can be seen that the larger the charcoal particles the more pronounced the Brownian motion is

Answer

Answer: B

Solution: A. According to the meaning of the question, every 30 s to observe the position of the charcoal particles recorded, and then use a straight line to connect these positions in turn into a folding line; therefore, the Brownian motion image is every 30 s the position of the solid particles, rather than the trajectory, but only according to the time interval to record the position of the connecting line in turn. Therefore, A is wrong; B. The movement of the small charcoal particles can be seen from the figure is irregular, so B is correct; C. Recorded by the impulse of the liquid molecules hit by the charcoal particles to do irregular movement, reflecting the liquid molecules of the thermal movement of the chaotic, so C error; D. The larger the charcoal particles, the more easily balanced by the impulse of the liquid molecules hit, the less significant Brownian motion, so D error. Therefore, choose B.

Question 8

Question 8: 8. Two molecules, which are very far apart, move in opposite directions with a certain initial veloc...

8. Two molecules, which are very far apart, move in opposite directions with a certain initial velocity until the distance is minimized. During this process, the two molecules interact with each other in the form of

A. A. Always for gravity.
B. B. Always for repulsion
C. C. Gravity first, then repulsion.
D. D. impossible judge

Answer

Answer: C

Solution: The variation of molecular force with distance is shown in the figure, so that as two molecules approach from a great distance apart, the molecular force behaves first as a gravitational force and then as a repulsive force.

Question 9

Question 9: 9. The following statements are correct

9. The following statements are correct

A. A. Diffusion is Brownian motion.
B. B. Brownian motion is a special case of diffusion
C. C. Brownian motion is molecular heat.
D. D. Diffusion phenomena, Brownian motion and molecular thermal motion all become violent with increasing temperature

Answer

Answer: D

Solution: Brownian motion is the motion of small solid particles, not the thermal motion of molecules; diffusion phenomenon is the thermal motion of molecules, option ABC is wrong; diffusion phenomenon, Brownian motion and the thermal motion of molecules with the increase in temperature and become violent, option D is correct; therefore, choose D.

Question 10

Question 10: 10. The following statements about the internal energy of an object are correct

10. The following statements about the internal energy of an object are correct

A. A. Different objects, with equal temperatures, have equal internal energies.
B. B. The potential energy of all molecules increases, as does the internal energy of the object
C. C. As the temperature increases, the average kinetic energy of the molecules increases, but the internal energy does not necessarily increase
D. D. As long as the mass, temperature, and volume of two objects are equal, the internal energy of the two objects must be equal

Answer

Answer: C

Solution: Temperature is the sign of the average kinetic energy of molecules, the average kinetic energy of molecules at the same temperature of the object is the same, but the internal energy also includes the potential energy of molecules; so you can't say that the same temperature is the same as the internal energy is the same, so A is wrong; the potential energy of molecules increases, if the temperature is lowered, then the object's internal energy may be reduced or unchanged, so B is wrong; the temperature is the sign of the average kinetic energy of molecules, the temperature is higher, the average kinetic energy of molecules increases, but the internal energy also includes the potential energy of molecules The temperature is a sign of the average kinetic energy of molecules, the temperature increases, the average kinetic energy of molecules increases, but the internal energy also includes the potential energy of molecules, so the internal energy is not necessarily increased, so C is correct; the internal energy is also related to the amount of material, the same temperature, volume, the internal energy is not necessarily equal, so D error. Therefore, C is correct and ABD is wrong.

Question 11

Question 11: 11. The operating principle of the following electrical appliances involves the application of the e...

11. The operating principle of the following electrical appliances involves the application of the eddy current phenomenon.

A. A. hair dryer
B. B. induction cooker
C. C. refrigerator
D. D. TV sets

Answer

Answer: B

Solution: A. The hairdryer is made by using the principle that an energized conductor is rotated by force in a magnetic field, which is the same as the principle of an electric motor, A is wrong; B. The induction cooker uses periodic changes in the alternating current in the coil to produce induced currents in nearby conductors to heat the food, i.e., it uses the eddy current principle to heat the food, B is correct; C.The refrigerator is made using a compressor to compress the gas and using the principle of heat transfer, C is incorrect; D. Television sets work by using the principles of emission and reception of electromagnetic waves and the deflection of charged particles in an electric field, D is wrong.

Question 12

Question 12: 12. One of the following statements is correct

12. One of the following statements is correct

A. A. The larger a solid particle suspended in a liquid is, the more liquid molecules will hit it at a given instant, and the more pronounced the Brownian motion will be
B. B. Knowing the molar mass of water and the mass of a single water molecule, Avogadro's constant can be calculated
C. C. Knowing the molar volume of a gas $V$ and knowing Avogadro's constant you can find the volume of a gas molecule
D. D. As the temperature rises, the average kinetic energy of the thermal motion of the molecules must increase, and the rate of all molecules increases

Answer

Answer: B

Solution: A. The larger the particles suspended in the liquid, the more the number of liquid molecules colliding with it at a certain moment, the more unbalanced the impact is less obvious, the less obvious Brownian motion. Therefore, A error; B. The ratio of the molar mass of water to the mass of a water molecule is equal to Avogadro's constant, so B is correct; C. known molar volume of a gas and Avogadro's constant, you can find a gas molecule occupies the size of the space, because the distance between the gas molecules is relatively large, so you can not calculate the volume of the molecules, so C error; D. The average kinetic energy of molecules must increase when the temperature rises, but not all molecules of the rate increases, the rate of individual molecules may decrease, so D error.

Question 13

Question 13: 13. One of the following statements is correct

13. One of the following statements is correct

A. A. As the temperature of an object increases, the object contains more heat
B. B. If the temperature of an object is constant, the internal energy must be constant
C. C. The units of heat and work are the same as the units of internal energy, so both heat and work are used as measures of an object's internal energy
D. D. Heat and work are determined by the process, while internal energy is determined by the state of the object

Answer

Answer: D

Solution: A. Heat is a process quantity, and you can't say how much heat an object contains, so A is wrong; B. The temperature of the object remains the same, the internal energy is not necessarily unchanged, for example, $0 ^ { \circ } \mathrm { C }$ of the ice into $0 ^ { \circ } \mathrm { C }$ of the water internal energy increased, B error; C. Work and heat are both measures of energy transformation, and both heat and work can be used as a measure of the change in internal energy of an object rather than a measure of internal energy, C is wrong; D. heat and work are determined by process, while internal energy is determined by the state of the object, D is correct.

Question 14

Question 14: 14. The following account of thermal phenomena is correct

14. The following account of thermal phenomena is correct

A. A. Brownian motion reflects the irregular motion of molecules in particles
B. B. When an object absorbs heat from the outside world, its internal energy must increase
C. C. Gas molecules are difficult to compress because of repulsive forces between molecules
D. D. The average kinetic energy of the molecules of an ideal gas of a given mass may increase as the pressure decreases

Answer

Answer: D

Solution: A. Brownian motion suspended in the liquid particles in motion, and particles are composed of a large number of molecules, so Brownian motion can not reflect the irregular movement of molecules in the particles, so A error; B. objects from the outside world to absorb heat, according to the first law of thermodynamics $$ \triangle U = Q + W $$ Analysis shows that its internal energy does not necessarily increase, but also with the work situation, so B error; C. Gas molecules are difficult to compress because of the pressure rather than intermolecular repulsion, so C error; D. A certain mass of ideal gas pressure decreases, according to the gas equation of state $$ \frac { p V } { T } = C $$ According to the equation of state of the gas $$ \frac { p V } { T } = C $$, if the volume increases, the temperature may increase and the average kinetic energy of the molecules may increase, so D is correct.

Question 15

Question 15: 15. The following statements about diffusion and Brownian motion are correct.

15. The following statements about diffusion and Brownian motion are correct.

A. A. Peppercorns tumble in a pot of boiling water, indicating that the higher the temperature the more violent Brown's movement is
B. B. Brownian motion proves that the molecules that make up the small particles of a solid move irregularly
C. C. Both free expansion and diffusion phenomena are reversible in both directions
D. D. The volume of water and alcohol after mixing is less than the sum of the volumes before mixing, indicating that there are gaps between the liquid molecules

Answer

Answer: D

Solution: A. Pepper tumbling in a pot of boiling water is the phenomenon of boiling water, and Brownian motion cannot be observed directly with the naked eye, A is wrong; B. Brownian motion is suspended in the gas or liquid solid particles in the irregular movement, reflecting the gas or liquid molecules of the irregular movement, so B error; C. and thermal phenomena related to the free expansion and diffusion phenomena are one-way irreversible, C error; D. half a test tube of water and half a test tube of alcohol after mixing the total volume to be less than the volume of the entire test tube, indicating that the liquid molecules are interstitial, D is correct.

Question 16

Question 16: 16. Move the oxygen cylinder from the cold outdoors to the warm indoors and leave it for a period of...

16. Move the oxygen cylinder from the cold outdoors to the warm indoors and leave it for a period of time, the oxygen in the bottle

A. A. The average kinetic energy of the molecules in thermal motion becomes smaller, and the pressure becomes smaller
B. B. The average kinetic energy of the molecules in thermal motion becomes smaller and the pressure increases
C. C. The average kinetic energy of the thermal motion of the molecules increases and the pressure decreases
D. D. The average kinetic energy of the molecules in thermal motion increases and the pressure becomes stronger

Answer

Answer: D

Solution: The oxygen cylinder is moved from the cold outdoor to the warm indoor and placed for a period of time, the temperature of the oxygen in the cylinder increases, the average kinetic energy of the thermal movement of the gas molecules increases; the volume of the cylinder remains unchanged, so the volume of oxygen remains unchanged, and according to Charlie's law, there are $$ \frac { p _ { 1 } } { T _ { 1 } } = \frac { p _ { 2 } } { T _ { 2 } } $$ It can be seen that the temperature increases, so the pressure of the gas becomes greater.

Question 17

Question 17: 17. air spring is a widely used in commercial automobiles, buses, high-speed railroads and building ...

17. air spring is a widely used in commercial automobiles, buses, high-speed railroads and building base shock absorbers, its basic structure and principle as shown in the figure, in the heat conduction of good cylinder and free sliding piston sealed between a certain mass of ideal gas, if the external temperature remains unchanged, slowly increase the mass of the weight, the following statements are correct ![](/images/questions/phys-kinetic-theory/image-004.jpg)

A. A. The pressure of the gas in the cylinder is always equal to the outside atmospheric pressure
B. B. The internal energy of the gas in the cylinder must have increased
C. C. The gas in the cylinder must absorb heat from the outside
D. D. Increase in the number of molecules impacted per unit time by the gas in the cylinder against the bottom of the cylinder

Answer

Answer: D

Solution: A. The mass of the piston is ${ } ^ { M }$, and according to the equilibrium condition, we can get $p S = p _ { 0 } S + ( M + m ) g$. The pressure of the gas in the cylinder is greater than the outside atmospheric pressure, so A is wrong; BC. Because the cylinder conducts heat well, the outside temperature remains unchanged, then the temperature of the gas inside the cylinder remains unchanged, the gas inside the cylinder The internal energy of the cylinder remains unchanged; slowly increase the mass of the weight, the pressure of the gas in the cylinder increases, according to $p V = C$, it can be seen that the volume of gas According to $p V = C$, the volume of the gas decreases, the outside world does positive work on the gas, and according to the first law of thermodynamics $\Delta U = W + Q$, it can be known that the gas in the cylinder releases heat from the outside world. The gas in the cylinder emits heat from the outside world, so BC is wrong; D. As the temperature of the gas in the cylinder remains unchanged, the average kinetic energy of the gas molecules is unchanged, and the pressure of the gas in the cylinder increases, according to the microscopic significance of the pressure can be known, the gas in the cylinder to the bottom of the cylinder within a unit of time to increase the number of molecules, so D is correct. Therefore, D is correct.

Question 18

Question 18: 18. The following statements about the molecular dynamics theory are correct

18. The following statements about the molecular dynamics theory are correct

A. A. Brownian motion is the irregular motion of molecules of small solid particles suspended in a liquid
B. B. The thermal motion of gas molecules is not necessarily more intense than that of liquid molecules
C. C. When a gas is compressed, it exhibits forces that resist compression because of repulsive forces between the gas molecules.
D. D. If the two systems are in thermal equilibrium, they must have the same internal energy

Answer

Answer: B

Solution: Brownian motion is suspended in the liquid solid particles of motion, not molecular motion, is due to the collision of liquid molecules around it, so Brownian motion is a reflection of the irregular thermal motion of the liquid molecules, but not the liquid molecules of the irregular movement, A error; molecular thermal motion intense degree and temperature, so the thermal motion of the gas molecules is not necessarily more intense than that of the liquid molecules of the thermal motion, B correct; gas compression can be ignored intermolecular forces, compression of gas will show resistance to compression is due to the gas pressure, and molecular forces have nothing to do, C error; if the two systems are in a thermal flat If the two systems are in thermal equilibrium, they must have the same temperature, but not the same internal energy, because it is also related to the mass, D error.

Question 19

Question 19: 19. When a certain mass of $0 ^ { \circ } \mathrm { C }$ ice melts into $0 ^ { \circ } \mathrm { C }...

19. When a certain mass of $0 ^ { \circ } \mathrm { C }$ ice melts into $0 ^ { \circ } \mathrm { C }$ water, the sum of the kinetic energies of the molecules $E _ { k }$ and the sum of the potential energies of the molecules $E _ { p }$ changes as follows

A. A. $E _ { k }$ becomes larger, $E _ { p }$ becomes larger
B. B. $E _ { k }$ becomes smaller, $E _ { p }$ becomes smaller
C. C. $E _ { k }$ unchanged, $E _ { p }$ larger
D. D. $E _ { k }$ becomes larger, $E _ { p }$ becomes smaller

Answer

Answer: C

Solution: Since the temperature remains the same, the average kinetic energy of the molecules is the same; since the melting of ice into water absorbs heat from the outside world, the potential energy of the molecules is different. $0 ^ { \circ } \mathrm { C }$ of ice melted into $0 ^ { \circ } \mathrm { C }$ of water need to absorb heat, so the same mass of $0 ^ { \circ } \mathrm { C }$ of water than $0 ^ { \circ } \mathrm { C }$ of the ice of the internal energy, that is, the E becomes larger; because the internal energy including molecular kinetic energy and molecular potential energy Since the temperature remains the same and the average kinetic energy of the molecules is the same, the molecular potential energy of water should be greater than that of ice; i.e., $\mathrm { E } _ { \mathrm { k } }$ does not change, and $\mathrm { E } _ { \mathrm { p } }$ becomes larger. A. $E _ { k }$ becomes larger, $E _ { p }$ becomes larger, which is inconsistent with the conclusion, option A is wrong; B.$E _ { k }$ becomes smaller, $E _ { p }$ becomes smaller, which is inconsistent with the conclusion, and option B is wrong; C. $E _ { k }$ does not change, $E _ { p }$ becomes larger, which is consistent with the conclusion, option C is correct; D. $E _ { k }$ becomes larger and $E _ { p }$ becomes smaller, which is inconsistent with the conclusion;

Question 20

Question 20: 20. The following statements are correct

20. The following statements are correct

A. A. Gases always fill the entire container easily, which is a macroscopic manifestation of the repulsive forces between molecules
B. B. When molecular forces behave as gravitational forces, the molecular potential energy decreases with increasing intermolecular distance
C. C. The sum of the kinetic and potential energies of 10 molecules is the internal energy of those 10 molecules.
D. D. Knowing Avogadro's constant and the molar mass of a substance, you can find the mass of the molecules of that substance

Answer

Answer: D

Solution: A. The distance between the gas molecules is very large, the molecular force is basically zero, the gas is easy to fill the container, which is the result of molecular thermal movement, so A error; B. When the molecular force is expressed as gravitational force, the distance between the molecules increases when the molecular force to do negative work, the molecular potential energy with the increase in the distance between the molecules and increase, so B error; C. The internal energy of the object is composed of all the molecules of the object's kinetic energy and molecular potential energy of the irregular thermal motion of the sum, with statistical significance, for a single or a few molecules have no significance, C error; D.Knowing Avogadro's constant and the molar mass of a substance can be determined by the $$ m = \frac { M } { N _ { A } } $$ to find the mass of the molecules of the substance, so D is correct.

Question 21

Question 21: 21. As shown in the figure, in the experiment demonstrating that work can change the internal energy...

21. As shown in the figure, in the experiment demonstrating that work can change the internal energy of a gas, the following statements are correct. ![](/images/questions/phys-kinetic-theory/image-005.jpg)

A. A. To slowly depress the piston to prevent damage to the cylinder
B. B. The experiment was conducted on the air in the cylinder
C. C. The observation that the ether caught fire indicates that the work done increased the internal energy of the cotton
D. D. The piston should be pressed down slowly

Answer

Answer: B

Solution: ACD. In order to reduce the impact of heat transfer, the piston should be quickly downward pressure piston, rapid downward pressure piston, the piston on the air inside the cylinder to do work, will be converted into mechanical energy inside the cylinder of the air's internal energy, so that the temperature of the air, indicating that the work can be done to change the internal energy of the object; the cylinder of the air and the heat transfer to the cotton, when the temperature of the cotton reaches the ignition point, the cotton will be burned, so the cotton increase in the internal energy by means of heat transfer to achieve B. Demonstrate that work can change the energy of a gas; B. Demonstration of work can change the internal energy of the gas, is the work of external forces on the air, the air's internal energy increased; the object of study is the cylinder of air, so B is correct.

Question 22

Question 22: 22. The following statements are true about energy

22. The following statements are true about energy

A. A. The internal energy of each molecule is equal to the sum of its potential and kinetic energy
B. B. Every form of motion of matter in nature has its corresponding energy
C. C. When energy is transferred or transformed, it must be accompanied by the process of doing work
D. D. When an object's internal energy changes, its temperature must change

Answer

Answer: B

Solution: Potential energy and kinetic energy are statistical concepts that have no meaning when spoken to individual molecules, $A$ is wrong; each form of motion of matter in nature has its corresponding energy, e.g., there is mechanical energy for motion, and molecular thermal motion consists of internal energy, $B$ is correct; the process of transferring or transforming energy does not necessarily involve work, such as heat transfer, $C$ is wrong; internal energy is not only affected by temperature, but also by the state of the object. For example, heat transfer, $C$ is wrong; the internal energy of the object is not only affected by the temperature, but also with the state in which the object is located, for example, zero degrees Celsius ice absorbs heat and changes into zero degrees Celsius water, the internal energy increases, the temperature remains unchanged, D is wrong; Therefore, choose B. [Eyes on] this question examines more knowledge, some options, as long as you can find some examples of support or opposition to determine whether it is correct or not .

Question 23

Question 23: 23. The following is a correct understanding that the thermal motion of gas molecules obeys a statis...

23. The following is a correct understanding that the thermal motion of gas molecules obeys a statistical law.

A. A. The regularity that a system consisting of a large number of gas molecules in disordered motion exhibits in the aggregate is called a statistical law
B. B. Statistical laws still apply to systems containing very few molecules
C. C. Statistical laws can be derived mathematically
D. D. Statistical laws apply only to the study of the thermal motion of gas molecules

Answer

Answer: A

Solution: ABC.The laws of statistics are the overall laws of a large number of chance events, which are meaningless for a small number of chance events, and the motion of a small number of gas molecules is unpredictable, so A is correct and BC is wrong. D. The laws of statistics apply to all studies of large numbers of chance events.

Question 24

Question 24: 24. Knowing the molar volume and Avogadro's constant of a gas at standard conditions, the physical q...

24. Knowing the molar volume and Avogadro's constant of a gas at standard conditions, the physical quantity that can be estimated is

A. A. Mass of gas molecules
B. B. Volume of gas molecules
C. C. Average distance between gas molecules
D. D. Density of gases

Answer

Answer: C

Solution: AD. To estimate the density of a gas or the mass of a gas molecule, you need to know the molar mass of the gas, so A and D are wrong; BC. The ratio of the molar volume of a gas to Avogadro's constant can be used to estimate the volume of space occupied by a gas molecule, while not the volume of a gas molecule, according to $$ d ^ { 3 } = \frac { V _ { 0 } } { N _ { A } } $$ The average distance between gas molecules can be estimated, so B is wrong and C is correct.

Question 25

Question 25: 25. The following statements are correct

25. The following statements are correct

A. A. Brownian motion is the irregular movement of liquid molecules
B. B. Only work done on an object from outside can increase its internal energy
C. C. The greater the relative humidity of the air, the greater the difference between the actual pressure of water vapor in the air and the saturation pressure of water at the same temperature, and the less likely that water will evaporate
D. D. For a given mass of gas, the average number of collisions per second of molecules per unit area of the wall increases with decreasing temperature at constant pressure

Answer

Answer: D

Solution: Brownian motion is suspended in the liquid surface of the solid particles of the irregular movement of the liquid molecules of the irregular movement of the performance, option A error; work and heat transfer can increase the internal energy of the object, option B error; when the relative humidity of the air is greater, the actual pressure of water vapor in the air is closer to the saturation vapor pressure of water at the same temperature, the more slowly the evaporation of water from the surface of the body, C error; a certain mass of the gas, the pressure of the gas in the Unchanged, the temperature of the gas decreases, the volume decreases, the density of molecules per unit volume of gas increases, the molecules per second on the wall of the average number of collisions per unit area as the temperature decreases and increases. Therefore, D is correct; so choose D.

Question 26

Question 26: 26. The following ways of changing the internal energy of an object are not considered to be work.

26. The following ways of changing the internal energy of an object are not considered to be work.

A. A. Rub your hands together. They'll feel warmer.
B. B. Gas in the cylinder of a gasoline engine is compressed
C. C. The iron chips cut by the lathe are hot.
D. D. Objects are heated in the sun

Answer

Answer: D

Solution: A. The process of rubbing your hands to feel them warmer belongs to the process of doing work to change internal energy, so A is wrong; B. The process of compressing the gas in the cylinder of a gasoline engine belongs to work to change internal energy, so B is wrong; C. The process of cutting down the iron filings of the car knife is hot belongs to do work to change the internal energy, so C is wrong; D, the object in the sun is hot process belongs to the heat radiation in the heat transfer, so D is correct;

Question 27

Question 27: 27. A gas bubble rises from the bottom of the lake to the surface, if the temperature remains consta...

27. A gas bubble rises from the bottom of the lake to the surface, if the temperature remains constant, the gas molecules in the bubble

A. A. Average kinetic energy decreases
B. B. Decrease in the average force per unit area on the bubble wall
C. C. Average kinetic energy increases
D. D. Increase in the average force per unit area on the bubble wall

Answer

Answer: B

Solution: AC. If the temperature of the bubble remains constant, the average kinetic energy remains constant, option AC is incorrect; BD. The bubble rises from the bottom to the surface of the lake, then the pressure of the gas inside the bubble decreases, then the average force per unit area on the bubble wall decreases, option B is correct, D is wrong.

Question 28

Question 28: 28. The figure shows an image of the change in volume $V$ of a certain mass of an ideal gas with the...

28. The figure shows an image of the change in volume $V$ of a certain mass of an ideal gas with the change in thermodynamic temperature $T$, then the following statements are true ![](/images/questions/phys-kinetic-theory/image-006.jpg)

A. A. From state $a$ to state $c$, the density of gas molecules decreases and then increases.
B. B. From state $a$ to state $c$, the average rate of gas molecules increases and then decreases.
C. C. Fewer molecules per unit time collide with the wall per unit area in state $d$ compared to state $b$.
D. D. The pressure of the gas in state $a$ is greater than the pressure of the gas in state $b$.

Answer

Answer: C

Solution: A. From state $a$ to state $c$, the volume of the gas becomes smaller and then larger, so the density of the gas molecules increases and then decreases, A is wrong; B. From state $a$ to state $c$, the temperature of the gas increases, so the average kinetic energy of the gas molecules increases, and the average rate of the molecules increases, B is wrong; C. The volume in state $d$ is larger than that in state $b$, the density of molecules in state $d$ is low, and the temperature is equal to that in state $d$. FORMULA_10]], and the average molecular rates are the same, then the number of molecules colliding with the wall per unit area per unit time is less in state $d$ than in state $b$, and C is correct; D. According to $$ \frac { P V } { T } = C $$ it can be known that $$ \frac { V } { T } = \frac { 1 } { P } C $$ The slope of the line connecting the point on the image of $V - T$ to the origin is proportional to the reciprocal of the pressure, the slope of the state $a$ is greater than the slope of the state $b$, the pressure of the gas in the state $a$ is less than the pressure of the gas in the state $b$, D is wrong. The pressure of the gas in state $b$ is less than the pressure of the gas in state $b$, D is wrong.

Question 29

Question 29: 29. The following statements about thermal phenomena and internal energy are correct

29. The following statements about thermal phenomena and internal energy are correct

A. A. Lifting an object slowly increases its mechanical energy and increases its internal energy
B. B. When current passes through a resistor, the resistor heats up and its internal energy increases by "doing work".
C. C. When a container of gas is accelerated, the internal energy of the gas in the container must increase.
D. D. The molecular potential energy is greatest when the gravitational and repulsive forces between molecules are equal

Answer

Answer: B

Solution: AC. Internal energy is the statistical average of the sum of the energy of irregular molecular motion, the energy of irregular molecular motion includes the kinetic energy of molecules, the potential energy of intermolecular interactions, and the energy of internal molecular motion, the internal energy of an object does not include the kinetic energy of the overall motion of the object and the potential energy of the object in the gravitational field, therefore, AC is incorrect; B. The resistance heats up after the current passes through the resistor because of the work done by the electric field on the free electrons in the conductor, so B is correct; D. Intermolecular gravitational and repulsive forces are equal, the molecular potential energy is minimized, so D error;

Question 30

Question 30: 30. Carbon dioxide transcritical direct cooling ice production" is the Beijing Winter Olympics "Chin...

30. Carbon dioxide transcritical direct cooling ice production" is the Beijing Winter Olympics "Chinese program", the figure of the National Speed Skating Hall $5000 \mathrm {~m} ^ { 2 }$ of the ice and all made of it, the temperature difference between the surface of the ice can be controlled in $\pm 0.5 ^ { \circ } \mathrm { C }$ within the $\pm 0.5 ^ { \circ } \mathrm { C }$. FORMULA_1]] within. The ice-making process can be simplified as a circular process in the figure, where the horizontal axis for the temperature $T$, the vertical axis for the pressure $p$; process $\mathrm { A } \rightarrow \mathrm { B } :$ A certain amount of carbon dioxide in the compressor under the action of the high temperature and high pressure of the supercritical state (a kind of between the liquid state and gas), the molecules have strong interactions with each other, and the ice is made from it. Process $\mathrm { B } \rightarrow \mathrm { C }$: Carbon dioxide undergoes a constant pressure process in the condenser and turns into a high pressure liquid; Process $\mathrm { C } \rightarrow \mathrm { D } :$ Carbon dioxide enters the evaporator and evaporates, which in turn causes the water in contact with the evaporator to cool down and solidify; Process $\mathrm { B } \rightarrow \mathrm { C }$: Carbon dioxide undergoes a constant pressure process in the evaporator and becomes a high pressure liquid. INLINE_FORMULA_7]]; the carbon dioxide undergoes a constant pressure process to return to its initial state. The following statement is correct. ![](/images/questions/phys-kinetic-theory/image-007.jpg) ![](/images/questions/phys-kinetic-theory/image-008.jpg) $A$. The kinetic energy of each carbon dioxide molecule will increase during the $A \rightarrow B$ process

A. A. Carbon dioxide transcritical direct cooling ice production" is the Beijing Winter Olympics "Chinese program", the picture of the National Speed Skating Stadium $5000 \mathrm {~m} ^ { 2 }$ of the ice and all made of it, the temperature difference between the surface of the ice can be controlled in $\pm 0.5 ^ { \circ } \mathrm { C }$ within the $\pm 0.5 ^ { \circ } \mathrm { C }$. FORMULA_1]] within. The ice-making process can be simplified as a circular process in the figure, where the horizontal axis for the temperature $T$, the vertical axis for the pressure $p$; process $\mathrm { A } \rightarrow \mathrm { B } :$ A certain amount of carbon dioxide in the compressor under the action of the high temperature and high pressure of the supercritical state (a kind of between the liquid state and gas), the molecules have strong interactions with each other, and the ice is made from it. process $\mathrm { B } \rightarrow \mathrm { C }$: carbon dioxide undergoes a constant pressure process in the condenser and turns into a high-pressure liquid; process $\mathrm { C } \rightarrow \mathrm { D } :$ carbon dioxide enters the evaporator to evaporate, which in turn causes the water in contact with the evaporator to cool down and solidify; process $\mathrm { D } \rightarrow \mathrm { A }$ carbon dioxide is evaporated by the evaporator; process [[]] carbon dioxide is evaporated by the evaporator; process [[]] carbon dioxide is evaporated by the evaporator; process [[]] carbon dioxide is evaporated by the evaporator INLINE_FORMULA_7]]
B. B. During the process $B \rightarrow C$, carbon dioxide always follows the experimental law of ideal gases
C. C. In the process $\mathrm { D } \rightarrow \mathrm { A }$, if carbon dioxide can be regarded as an ideal gas, then carbon dioxide will absorb heat in this process
D. D. Throughout the cycle, heat is transferred from low-temperature water to high-temperature carbon dioxide, violating the second law of thermodynamics

Answer

Answer: C

Solution: A. In the process $A \rightarrow B$, the average kinetic energy of the carbon dioxide molecules will increase as the temperature rises, but not every carbon dioxide molecule will have an increased kinetic energy, so A is wrong; $B$. In $B \rightarrow C$, carbon dioxide in $C$ is a liquid, not a gas, so it does not fulfill the conditions of the ideal gas law, so B is wrong; C. In the process $\mathrm { D } \rightarrow \mathrm { A }$, if carbon dioxide can be regarded as an ideal gas, the pressure is unchanged, the temperature rises, the volume increases, because the temperature rises, so the internal energy of carbon dioxide increases, but also because of the volume increases, carbon dioxide does work on the outside, so the carbon dioxide in the process of carbon dioxide will absorb heat, so C is correct; D. The whole cycle, heat transfer from low-temperature water to high-temperature carbon dioxide, the process caused by other changes, so it does not violate the second law of thermodynamics, so D is wrong.

Question 31

Question 31: 31. As shown in the figure is the relationship between the intermolecular interaction force and the ...

31. As shown in the figure is the relationship between the intermolecular interaction force and the intermolecular distance, in which the two dashed lines indicate the relationship between the intermolecular repulsive force and gravitational force and the intermolecular distance, respectively, and the solid line indicates the relationship between the intermolecular force (the combination of the repulsive force and the gravitational force) and the intermolecular distance, from the figure, the following statements are wrong. ![](/images/questions/phys-kinetic-theory/image-009.jpg)

A. A. No interaction between molecules when the intermolecular distance is ${ } ^ { r }$
B. B. The gravitational force between molecules is always greater than the repulsive force when the intermolecular distance is greater than ${ } ^ { r _ { 0 } }$
C. C. When the distance between molecules increases, the intermolecular force may first decrease, then increase and then decrease again
D. D. When the intermolecular distance is greater than ${ } ^ { r _ { 0 } }$, the intermolecular force always does negative work when the intermolecular distance is increased.

Answer

Answer: A

Solution: A. The repulsive force and gravitational force between molecules exist at the same time, and when the distance between molecules is $r _ { 0 }$, the gravitational force between molecules and the repulsive force are equal in magnitude, so A is consistent with the meaning of the question; B. By the solid line in the figure: when $r > r _ { 0 }$, the distance between molecules decreases, the gravitational force between molecules is always greater than the repulsive force, the molecular force is manifested as the gravitational force, so B does not meet the meaning of the question; C. When the distance between molecules increases, when $r > r _ { 0 }$, the molecular force first increases and then decreases when the distance between molecules decreases. When $r < r _ { 0 }$ is $r < r _ { 0 }$, the molecular force increases when the distance between the molecules decreases, so C does not meet the meaning of the question; D . D. When the distance between molecules is greater than $r _ { 0 }$, the molecular force manifests itself as a gravitational force, and when the distance between molecules is increased, the intermolecular force always does negative work. Therefore, D does not match the meaning of the question.

Question 32

Question 32: 32. In a darker room, the motion of particles suspended in the air directly visible to the eye from ...

32. In a darker room, the motion of particles suspended in the air directly visible to the eye from an incoming beam of light is (

A. A. Brownian motion
B. B. Thermal motion of molecules
C. C. free-fall motion
D. D. Motion caused by a combination of air currents and gravity

Answer

Answer: D

Solution: A. Brownian motion means that particles are invisible to the naked eye, so the motion of particles in the air that can be seen by the naked eye is not Brownian motion, A is wrong; B. The particles suspended in the air are not molecules, which is not the thermal movement of molecules, B error; CD. free-fall motion refers to the role of gravity only, the initial speed of zero movement, air resistance is ignored, and particles in the air is subject to a lot of force, so it is not free fall, C error, D is correct.

Question 33

Question 33: 33. Diamond is the main material in jewelry, high-strength drills, carving knives and other tools, l...

33. Diamond is the main material in jewelry, high-strength drills, carving knives and other tools, let the density of the diamond is $\rho$ (in units of $\mathrm { kg } / \mathrm { m } ^ { 3 }$), the molar mass is $M$ (in units of $\mathrm { g } / \mathrm { mol }$) and Avogadro's constant is $N _ { \mathrm { A } }$. Knowing that 1 carat is equal to 0.2 grams, ( )

A. A. $a$ The number of molecules contained in a carat diamond is $\frac { 02 \times 10 ^ { - 3 } a N _ { \mathrm { A } } } { M }$
B. B. $a _ { \text {克拉钻石所含有的分子数为 } } a N _ { \mathrm { A } }$
C. C. The expression for the diameter of each diamond molecule is $\sqrt [ 3 ] { \frac { 6 M \times 10 ^ { - 3 } } { N _ { \mathrm { A } } \rho \pi } }$ (in ${ } _ { \mathrm { m } }$ units)
D. D. The expression for the diameter of each diamond molecule is $\sqrt { \frac { 6 M } { N _ { \mathrm { A } } \rho \pi } }$ (in ${ } _ { \mathrm { m } }$ units)

Answer

Answer: C

Solution: $\mathrm { AB } . a$ The number of molecules contained in a carat diamond is $$ n = \frac { 02 a } { M } N _ { \mathrm { A } } $$ Therefore, AB is wrong; CD . The volume of each diamond molecule is $$ V _ { 0 } = \frac { M \times 10 ^ { - 3 } } { \rho N _ { A } } $$ Since the diamond molecule is modeled as a sphere, the $$ V _ { 0 } = \frac { 1 } { 6 } \pi d ^ { 3 } $$ Solve for the diameter of each diamond molecule $$ d = \sqrt [ 3 ] { \frac { 6 M \times 10 ^ { - 3 } } { N _ { \mathrm { A } } \rho \pi } } \text { (单位为 } \mathrm { m } \text { ) } $$ Therefore, C is correct and D is incorrect.

Question 34

Question 34: 34. Diamond is the main material in jewelry and high-strength drills, carving knives and other tools...

34. Diamond is the main material in jewelry and high-strength drills, carving knives and other tools, let the density of the diamond is $\rho$ (in units of $\mathrm { kg } / \mathrm { m } ^ { 3 }$), the molar mass is $M$ (in units of $\mathrm { g } / \mathrm { mol }$) and Avogadro's constant is $N _ { A }$. If 1 carat $= 0.2$ gram is known, then ( )

A. A. $a$ The number of molecules contained in a carat diamond is $\frac { 0.2 a N _ { \mathrm { A } } } { M }$
B. B. $a$ The number of molecules contained in a carat diamond is $\frac { a N _ { \mathrm { A } } } { M }$
C. C. The expression for the diameter of each diamond molecule is $\sqrt [ 3 ] { \frac { 9 M \times 10 ^ { - 3 } } { N _ { \wedge } \rho \pi } }$ (in m )
D. D. The expression for the diameter of each diamond molecule is $\sqrt { \frac { 6 M } { N _ { \mathrm { A } } \rho \pi } }$ (in m )

Answer

Answer: A

Solution: $\mathrm { AB } . a$ The amount of carat diamond substance (in moles) is $$ n = \frac { 0.2 a } { M } $$ The number of molecules contained is $$ N = n N _ { A } = \frac { 0.2 a N _ { A } } { M } $$ Option A is correct and B is incorrect; CD. The molar volume of a diamond $$ V = \frac { M \times 10 ^ { - 3 } } { \rho } \text { (单位为 } \mathrm { m } ^ { 3 } / \mathrm { mol } \text { ) } $$ Each diamond molecule has a volume of $$ V _ { 0 } = \frac { V } { N _ { A } } = \frac { M \times 10 ^ { - 3 } } { \rho N _ { A } } $$ Let the diameter of a diamond molecule be $d$, then $$ V _ { 0 } = \frac { 4 } { 3 } \pi \left( \frac { d } { 2 } \right) ^ { 3 } $$ The solution is $$ d = \sqrt [ 3 ] { \frac { 6 M \times 10 ^ { - 3 } } { N _ { \mathrm { A } } \rho \pi } } \text { (单位为 } \mathrm { m } \text { ) } $$ Option CD is wrong ;

Question 35

Question 35: 35. With regard to the molecular dynamics theory, the following statements are correct ( )

35. With regard to the molecular dynamics theory, the following statements are correct ( )

A. A. Lower the temperature to $0 ^ { \circ } \mathrm { C }$ and the molecular thermal motion will stop
B. B. The motion of the dust seen in the sunlight coming through the cracks into the classroom is Brownian motion
C. C. The higher the temperature, the more intense the diffusion phenomenon and Brownian motion.
D. D. The volume of an oxygen molecule is equal to the molar volume of oxygen divided by Avogadro's constant

Answer

Answer: C

Solution: A. The molecules of an object never stop moving in an irregular manner. When the temperature drops to $0 ^ { \circ } \mathrm { C }$, the thermal movement of the molecules will not stop, so A is wrong; B. Dust movement is caused by air flow, not Brownian motion, so B error; C. Diffusion phenomenon and Brownian motion reflect the irregular movement of molecules, the higher the temperature, the more intense molecular thermal movement, diffusion phenomenon and Brownian motion is also more intense, so C is correct; D. As the spacing of gas molecules is greater than the molecular diameter, so the molar volume of oxygen divided by Avogadro's constant is an oxygen molecule occupied by the volume, not the volume of oxygen molecules, so D error.

Question 36

Question 36: 36. A certain mass of gas for isovolumetric changes, the temperature increases, the gas pressure inc...

36. A certain mass of gas for isovolumetric changes, the temperature increases, the gas pressure increases due to the

A. A. The average impact of molecules on the vessel wall becomes larger
B. B. The gas molecules become denser and the molecules repel more against the walls of the vessel
C. C. Gas molecules become denser and the mass of molecules per unit volume becomes greater
D. D. The number of molecules per unit volume becomes larger and the number of collisions per unit time against the walls of the vessel becomes larger

Answer

Answer: A

Solution: The volume of the gas is constant, the density of the gas molecules is constant, the number of molecules per unit volume is constant, the temperature of the gas increases, the average kinetic energy of the molecules increases, the average rate of the gas becomes larger, and the average impact of the molecules on the wall of the vessel becomes larger according to the momentum theorem. Therefore, choose A.

Question 37

Question 37: 37. The following four figures are correctly stated ![](/images/questions/phys-kinetic-theory/image...

37. The following four figures are correctly stated ![](/images/questions/phys-kinetic-theory/image-010.jpg) A ![](/images/questions/phys-kinetic-theory/image-011.jpg) B ![](/images/questions/phys-kinetic-theory/image-012.jpg) C ![](/images/questions/phys-kinetic-theory/image-013.jpg) D

A. A. The distance between the molecules in figure A is $r _ { 0 }$ when the intermolecular repulsive force and gravitational force are zero, and the molecular potential energy is also zero
B. B. In figure B, to make the glass plate leave the water surface, the tension of the rope on the glass plate must be greater than the gravity of the glass plate.
C. C. The distance between molecules on the surface of the liquid in Figure C is greater than the distance between molecules inside the liquid, and there is only gravitational force between molecules on the surface of the liquid, not repulsive force
D. D. In Figure D, the outlet of the syringe is closed, and the resistance increases during the pressing of the closed gas in the tube, indicating an increase in the repulsive force between the gas molecules.

Answer

Answer: B

Solution: A. The distance between molecules in Figure A is $r _ { 0 }$, the intermolecular repulsion and gravity are equal, the molecular force is zero, the molecular potential energy is minimum, but not zero, option A is wrong; B. B figure because the glass plate and water molecules have a gravitational effect, then want to make the glass plate out of the water, the rope must be greater than the plate's gravity, option B is correct; C. As the distance between the liquid surface molecules is greater than the distance between the molecules within the liquid, the liquid surface intermolecular gravitational force is greater than the repulsive force, intermolecular gravitational force and repulsive force at the same time, the surface of the liquid has a tendency to shrink, then C is wrong; D. D. Figure in the closed syringe outlet, press the closed gas inside the tube in the process of resistance increases, which is the cause of the gas pressure, and gas intermolecular repulsion has nothing to do, option D is wrong.

Question 38

Question 38: 38. As shown in the figure, $a$ is a wire loop with a cotton thread tied loosely in the center; figu...

38. As shown in the figure, $a$ is a wire loop with a cotton thread tied loosely in the center; figure b is a wire loop soaked in soapy water; Figure $c$ shows that the left side of the cotton thread is lightly touched with a finger; Figure $d$ shows that the soap film on the left side of the cotton thread breaks, and the cotton thread is pulled to the right side. ![](/images/questions/phys-kinetic-theory/image-014.jpg) a ![](/images/questions/phys-kinetic-theory/image-015.jpg) b ![](/images/questions/phys-kinetic-theory/image-016.jpg) c ![](/images/questions/phys-kinetic-theory/image-017.jpg) d

A. A. Matter is made up of a large number of molecules
B. B. Gravity exists between molecules.
C. C. The molecules that make up matter are constantly in irregular motion
D. D. There are gaps between the molecules

Answer

Answer: B

Solution: Touch the left side of the cotton thread with your finger, the left side of the soap film broke, due to the right side of the soap film and the cotton thread between the molecules have a strong role, so the cotton thread will be pulled to the right, indicating the existence of molecules of mutual gravitational force.

Question 39

Question 39: 39. When the distance between molecules is ${ } ^ { r }$, the force between molecules is zero. As th...

39. When the distance between molecules is ${ } ^ { r }$, the force between molecules is zero. As the intermolecular distance increases from ${ } ^ { 0.9 r _ { 0 } }$ to ${ } ^ { 10 r _ { 0 } }$, the intermolecular force is zero.

A. A. ${ } ^ { 0.9 r _ { 0 } }$ to ${ } ^ { r _ { 0 } }$, the intermolecular force is gravitational
B. B. $r _ { 0 }$ to $^ { 10 r _ { 0 } }$, the intermolecular force decreases
C. C. ${ } ^ { 0.9 r _ { 0 } }$ to $r _ { 0 }$, the molecular potential energy decreases, and the molecular potential energy decreases slower and slower with the increase in spacing
D. D. $r _ { 0 }$ to $10 r _ { 0 }$, the molecular potential energy increases, and the molecular potential energy increases more and more rapidly with increasing spacing

Answer

Answer: C

Solution: A. As the distance between molecules increases from ${ } ^ { 0.9 r _ { 0 } }$ to $r _ { 0 }$, the molecular force manifests itself as repulsion, and the size of the molecular force gradually decreases, so A is wrong; B. As the distance between molecules increases from ${ } ^ { r _ { 0 } }$ to ${ } ^ { 10 r _ { 0 } }$, the molecular force manifests itself as a repulsive force, and the magnitude of the molecular force increases and then decreases, so B is wrong; C. The distance between molecules from ${ } ^ { 0.9 r _ { 0 } }$ increased to $r _ { 0 }$ process, molecular force is reflected in the repulsive force, the molecular force to do positive work, molecular potential energy decreases, molecular force gradually decreases in size, it can be seen that with the increase in the distance between the molecular potential energy decreases more and more slowly, so C is correct; D. The distance between the molecules from ${ } ^ { r _ { 0 } }$ to ${ } ^ { 10 r }$ process, the molecular force is embodied in the gravitational force, the molecular force to do the negative work, the molecular potential energy increases, the molecular force size increases first and then decreases, it can be seen that with the increase in the spacing of the molecular potential energy increases the rate of the first fast and then slow, the D error.

Question 40

Question 40: 40. A student in order to perform "lightweight", he stood on a lightweight hard plate placed by the ...

40. A student in order to perform "lightweight", he stood on a lightweight hard plate placed by the balloon cushion, as shown in the figure. The balloon is filled with air (regarded as an ideal gas), the pressure of the gas ![](/images/questions/phys-kinetic-theory/image-018.jpg) High School Physics Assignment, October 30, 2025

A. A. is produced by the force of gravity on the gas
B. B. It is produced by a large number of gas molecules constantly colliding with the walls of the vessel
C. C. The size depends only on the number of gas molecules
D. D. The size depends only on the gas temperature.

Answer

Answer: B

Solution: AB . As a large number of molecules are constantly doing irregular thermal movement, and the wall of the frequent collisions, so that the wall is subjected to an average sustained impulse, resulting in the gas on the wall to produce a certain pressure, A error B correct; CD.Based on the microscopic significance of pressure, it can be seen that the size of the pressure depends on the number of gas molecules and the temperature of the gas, CD is wrong.

Kinetic Theory of Gases

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