Transcript ILQ-Ch

Halliday/Resnick/Walker
Fundamentals of Physics
Classroom Response System Questions
Chapter 20 Entropy and the Second Law of
Thermodynamics
Interactive Lecture Questions
20.2.1. A leaf is growing on a tree. Does this growth process violate the second
law of thermodynamics when it is stated in terms of entropy?
a) Yes, but the law does not apply to living things. It only applies to inanimate
objects.
b) Yes, because this law is not applicable in situations involving radiant energy
from the Sun.
c) No, because the entropy of the Sun has decreased while the entropy of the
leaf increases as it grows.
d) No, because while the entropy of the leaf is decreasing as it grows, there is a
net increase in entropy because of the light emitted from the leaf.
e) No, because there is no net increase in the energy of the leaf.
20.2.1. A leaf is growing on a tree. Does this growth process violate the second
law of thermodynamics when it is stated in terms of entropy?
a) Yes, but the law does not apply to living things. It only applies to inanimate
objects.
b) Yes, because this law is not applicable in situations involving radiant energy
from the Sun.
c) No, because the entropy of the Sun has decreased while the entropy of the
leaf increases as it grows.
d) No, because while the entropy of the leaf is decreasing as it grows, there is a
net increase in entropy because of the light emitted from the leaf.
e) No, because there is no net increase in the energy of the leaf.
20.2.2. While watching a fantasy film, you observe a wizard wave his arms
and six potion vials that had fallen to the floor suddenly piece
themselves back together with the potions inside and rise up with a table.
In the end, the table is upright and the six vials with their potions are
sitting on the table as if nothing had happened. Which of the following
principles or laws of physics is disobeyed by this scene from the movie?
a) conservation of energy
b) second law of thermodynamics
c) Newton’s laws of motion
d) time dilation
e) the work-energy theorem
20.2.2. While watching a fantasy film, you observe a wizard wave his arms
and six potion vials that had fallen to the floor suddenly piece
themselves back together with the potions inside and rise up with a table.
In the end, the table is upright and the six vials with their potions are
sitting on the table as if nothing had happened. Which of the following
principles or laws of physics is disobeyed by this scene from the movie?
a) conservation of energy
b) second law of thermodynamics
c) Newton’s laws of motion
d) time dilation
e) the work-energy theorem
20.3.1. A box with five adiabatic sides contains an ideal gas with an initial
temperature T0. The sixth side is diathermal and is placed in contact with a
reservoir with a constant temperature T2 > T0. Assuming the specific heat
capacity of the system does not change with temperature, why must the entropy
change of the universe always be increasing as the box warms?
a) Entropy will always be increasing since the work done on the gas in the box is
negative.
b) Entropy will always be increasing since the temperature of the box is always less
than or equal to T2.
c) Entropy will always be increasing since this process is reversible.
d) Entropy will always be increasing since the temperature of the box is always
greater than absolute zero.
e) Entropy will always be increasing since in any process entropy increases.
20.3.1. A box with five adiabatic sides contains an ideal gas with an initial
temperature T0. The sixth side is diathermal and is placed in contact with a
reservoir with a constant temperature T2 > T0. Assuming the specific heat
capacity of the system does not change with temperature, why must the entropy
change of the universe always be increasing as the box warms?
a) Entropy will always be increasing since the work done on the gas in the box is
negative.
b) Entropy will always be increasing since the temperature of the box is always less
than or equal to T2.
c) Entropy will always be increasing since this process is reversible.
d) Entropy will always be increasing since the temperature of the box is always
greater than absolute zero.
e) Entropy will always be increasing since in any process entropy increases.
20.3.2. An ideal gas is compressed as it is held at constant
temperature. Which one of the following statements concerning
this situation is true?
a) No work is done on the gas during this process.
b) Heat is transferred out of the gas.
c) The internal energy of the gas is constant during this process.
d) Choices (a) and (b) are both correct.
e) Choices (b) and (c) are both correct.
20.3.2. An ideal gas is compressed as it is held at constant
temperature. Which one of the following statements concerning
this situation is true?
a) No work is done on the gas during this process.
b) Heat is transferred out of the gas.
c) The internal energy of the gas is constant during this process.
d) Choices (a) and (b) are both correct.
e) Choices (b) and (c) are both correct.
20.3.3. Two containers with thermally insulating walls are connected by a
valve. One of the containers is completely evacuated; and the other is
filled with an ideal gas. How does the temperature of the gas after the
valve is opened and equal amounts of gas occupy both containers
compare to the temperature of the gas before the valve was opened?
a) The final temperature will be greater than the initial temperature.
b) The final temperature will be less than the initial temperature.
c) The final temperature will be the same as the initial temperature.
d) This cannot be answered without knowing the initial volumes of the two
containers.
e) This cannot be answered without knowing the initial pressure of the gas.
20.3.3. Two containers with thermally insulating walls are connected by a
valve. One of the containers is completely evacuated; and the other is
filled with an ideal gas. How does the temperature of the gas after the
valve is opened and equal amounts of gas occupy both containers
compare to the temperature of the gas before the valve was opened?
a) The final temperature will be greater than the initial temperature.
b) The final temperature will be less than the initial temperature.
c) The final temperature will be the same as the initial temperature.
d) This cannot be answered without knowing the initial volumes of the two
containers.
e) This cannot be answered without knowing the initial pressure of the gas.
20.3.4. Which one of the following statements concerning the internal energy of a
system is true?
a) Thermal energy at a lower pressure can be considered “higher quality” energy
because it can do more work than thermal energy at a higher pressure.
b) Thermal energy at a lower temperature can be considered “higher quality” energy
because it can do more work than thermal energy at a higher temperature.
c) Thermal energy at a higher pressure can be considered “higher quality” energy
because it can do more work than thermal energy at a lower pressure.
d) Thermal energy at a higher temperature can be considered “higher quality”
energy because it can do more work than thermal energy at a lower temperature.
e) Thermal energy at a higher entropy can be considered “higher quality” energy
because it can do more work than thermal energy at a lower entropy.
20.3.4. Which one of the following statements concerning the internal energy of a
system is true?
a) Thermal energy at a lower pressure can be considered “higher quality” energy
because it can do more work than thermal energy at a higher pressure.
b) Thermal energy at a lower temperature can be considered “higher quality” energy
because it can do more work than thermal energy at a higher temperature.
c) Thermal energy at a higher pressure can be considered “higher quality” energy
because it can do more work than thermal energy at a lower pressure.
d) Thermal energy at a higher temperature can be considered “higher quality”
energy because it can do more work than thermal energy at a lower temperature.
e) Thermal energy at a higher entropy can be considered “higher quality” energy
because it can do more work than thermal energy at a lower entropy.
20.5.1. An automobile engine that burns gasoline has been engineered
to have a relatively high efficiency of 22 %. While a car is being
driven along a road on a long trip, 14 gallons of gasoline are
consumed by the engine. Of the 14 gallons, how much gasoline
was used in doing the work of propelling the car?
a) 14 gallons
b) about 11 gallons
c) about 8 gallons
d) about 3 gallons
e) about 1 gallon
20.5.1. An automobile engine that burns gasoline has been engineered
to have a relatively high efficiency of 22 %. While a car is being
driven along a road on a long trip, 14 gallons of gasoline are
consumed by the engine. Of the 14 gallons, how much gasoline
was used in doing the work of propelling the car?
a) 14 gallons
b) about 11 gallons
c) about 8 gallons
d) about 3 gallons
e) about 1 gallon
20.5.2. Consider the various paths shown on the pressure-volume
graph. By following which of these paths, does the system do the
most work?
a) 1 to 2 to 4
b) 1 to 4
c) 1 to 3 to 4
d) Each of these paths results in the same amount of work done.
20.5.2. Consider the various paths shown on the pressure-volume
graph. By following which of these paths, does the system do the
most work?
a) 1 to 2 to 4
b) 1 to 4
c) 1 to 3 to 4
d) Each of these paths results in the same amount of work done.
20.5.3. During the power stroke of an internal combustion engine, the air-fuel
mixture is ignited and the expanding hot gases push on the piston. Fuel
efficiency is maximized in this process when the ignited gas is as hot as
possible, the gas expands allowing a maximum amount of work to be done, and
cooled exhaust gas is released at the end of the cycle. Assuming the engine
exhibits the highest efficiency possible, which of the following statements
concerning the exhaust gas must be true to avoid violating the second law of
thermodynamics?
a) The exhaust gas must be hotter than the outside air temperature.
b) The exhaust gas must be at the same pressure as the outside air.
c) The exhaust gas must be cooled to the same temperature as the outside air.
d) The exhaust gas must be cooled below the temperature of the outside air.
e) Real engines will always violate the second law of thermodynamics.
20.5.3. During the power stroke of an internal combustion engine, the air-fuel
mixture is ignited and the expanding hot gases push on the piston. Fuel
efficiency is maximized in this process when the ignited gas is as hot as
possible, the gas expands allowing a maximum amount of work to be done, and
cooled exhaust gas is released at the end of the cycle. Assuming the engine
exhibits the highest efficiency possible, which of the following statements
concerning the exhaust gas must be true to avoid violating the second law of
thermodynamics?
a) The exhaust gas must be hotter than the outside air temperature.
b) The exhaust gas must be at the same pressure as the outside air.
c) The exhaust gas must be cooled to the same temperature as the outside air.
d) The exhaust gas must be cooled below the temperature of the outside air.
e) Real engines will always violate the second law of thermodynamics.
20.6.1. A house that is heated using a heat pump with an ideal coefficient of performance loses heat
to its surroundings at a rate of Z1(Thouse  Tsurr.), where Z1 is a constant, Thouse is the temperature
inside the house; and Tsurr. is the temperature of its surroundings. In this process, heat is taken
from the surroundings and heats the house at a rate of Z2(Tout  Thouse) where Tout is the
temperature of the air output from the heat pump, which has a constant value. Which one of
the following expressions is equal to the efficiency of the heat pump?
a)
Tout
Tout  Tsurr.
b)
Tsurr.
Tsurr.  Tout
c)
Thouse
Tout  Tsurr.
d)
Thouse
Tsurr.  Thouse
e)
Tout
Tsurr.  Thouse
20.6.1. A house that is heated using a heat pump with an ideal coefficient of performance loses heat
to its surroundings at a rate of Z1(Thouse  Tsurr.), where Z1 is a constant, Thouse is the temperature
inside the house; and Tsurr. is the temperature of its surroundings. In this process, heat is taken
from the surroundings and heats the house at a rate of Z2(Tout  Thouse) where Tout is the
temperature of the air output from the heat pump, which has a constant value. Which one of
the following expressions is equal to the efficiency of the heat pump?
a)
Tout
Tout  Tsurr.
b)
Tsurr.
Tsurr.  Tout
c)
Thouse
Tout  Tsurr.
d)
Thouse
Tsurr.  Thouse
e)
Tout
Tsurr.  Thouse
20.6.2. An air conditioner pumps heat from a cold room to the hot outdoors in a three step cyclic process:
(1) Room temperature, low pressure refrigerant gas passes through a compressor and comes out with
increased temperature and increased pressure. The hot gas passes through piping on the outside,
where heat is rejected to the surroundings.
(2) The gas then passes through a narrower pipe before entering a compressor. Work is done by the
compressor to increase the pressure enough for the gas to turn into a liquid.
(3) The liquid then undergoes free expansion into a gas and cools. The cool gas passes through pipes that
are inside the house. The inside air is cooled by coming into contact with these pipes. The
refrigerant gas exits these pipes as a room temperature, low pressure gas. The cycle is then repeated.
Why doesn’t this system violate the second law of thermodynamics?
a) The internal energy of the gas is constant.
b) Heat is normally taken from a warm place and transported to a warmer place.
c) The system involves a closed cycle.
d) Work is continually done on the system.
e) Since the compressor adds entropy, the total entropy increases.
20.6.2. An air conditioner pumps heat from a cold room to the hot outdoors in a three step cyclic process:
(1) Room temperature, low pressure refrigerant gas passes through a compressor and comes out with
increased temperature and increased pressure. The hot gas passes through piping on the outside,
where heat is rejected to the surroundings.
(2) The gas then passes through a narrower pipe before entering a compressor. Work is done by the
compressor to increase the pressure enough for the gas to turn into a liquid.
(3) The liquid then undergoes free expansion into a gas and cools. The cool gas passes through pipes that
are inside the house. The inside air is cooled by coming into contact with these pipes. The
refrigerant gas exits these pipes as a room temperature, low pressure gas. The cycle is then repeated.
Why doesn’t this system violate the second law of thermodynamics?
a) The internal energy of the gas is constant.
b) Heat is normally taken from a warm place and transported to a warmer place.
c) The system involves a closed cycle.
d) Work is continually done on the system.
e) Since the compressor adds entropy, the total entropy increases.
20.6.3. You are repairing a window-style air conditioner in a closed
workroom. You succeed in getting it to work, but are called away soon
after you turn it on. Unfortunately, you are unable to return for several
hours to turn it off. Assuming that it was running as efficiently as
possible while you were away, how has the temperature of the workroom
changed in your absence?
a) The room is somewhat cooler than before I left.
b) The room is slightly cooler than before I left.
c) The temperature of the room has not changed.
d) The room is warmer than before I left.
e) The air near the ceiling will be very warm, but the air around the air
conditioner will be very cool.
20.6.3. You are repairing a window-style air conditioner in a closed
workroom. You succeed in getting it to work, but are called away soon
after you turn it on. Unfortunately, you are unable to return for several
hours to turn it off. Assuming that it was running as efficiently as
possible while you were away, how has the temperature of the workroom
changed in your absence?
a) The room is somewhat cooler than before I left.
b) The room is slightly cooler than before I left.
c) The temperature of the room has not changed.
d) The room is warmer than before I left.
e) The air near the ceiling will be very warm, but the air around the air
conditioner will be very cool.
20.6.4. A tray of water is placed into a freezer. As the water cools, its entropy
decreases and eventually it turns to ice. Why doesn’t this process violate the
second law of thermodynamics?
a) When the ice is later taken out and melted, the entropy will increase back to what
it was before the tray was put into the freezer.
b) The overall entropy increases due to the refrigerator chilling and eventually
freezing the water.
c) The entropy of the tray increases to offset the decrease in the entropy of the water.
d) The entropy of the water decreases, but upon freezing it increases to its previous
value.
e) The process as described does violate the second law of thermodynamics.
20.6.4. A tray of water is placed into a freezer. As the water cools, its entropy
decreases and eventually it turns to ice. Why doesn’t this process violate the
second law of thermodynamics?
a) When the ice is later taken out and melted, the entropy will increase back to what
it was before the tray was put into the freezer.
b) The overall entropy increases due to the refrigerator chilling and eventually
freezing the water.
c) The entropy of the tray increases to offset the decrease in the entropy of the water.
d) The entropy of the water decreases, but upon freezing it increases to its previous
value.
e) The process as described does violate the second law of thermodynamics.
20.6.5. Consider the following diagram of a system representing your kitchen. You have
just finished dinner and have placed the leftovers in the refrigerator. On the
diagram, “R” represents the inner workings of the refrigeration unit, Q1 and Q2
represent heat that is being transferred, and W is an amount of work. “L” represents
your leftovers. What are the correct directions for the arrows indicated by the
numbers “1” and “2?”
a) Arrow 1 points into the refrigerator and arrow 2 points out of the refrigerator.
b) Arrow 1 points out of the refrigerator and arrow 2 points into the refrigerator.
c) Arrow 1 points into the refrigerator and arrow 2 points into the refrigerator.
d) Arrow 1 points out of the refrigerator and arrow 2 points out of the refrigerator.
20.6.5. Consider the following diagram of a system representing your kitchen. You have
just finished dinner and have placed the leftovers in the refrigerator. On the
diagram, “R” represents the inner workings of the refrigeration unit, Q1 and Q2
represent heat that is being transferred, and W is an amount of work. “L” represents
your leftovers. What are the correct directions for the arrows indicated by the
numbers “1” and “2?”
a) Arrow 1 points into the refrigerator and arrow 2 points out of the refrigerator.
b) Arrow 1 points out of the refrigerator and arrow 2 points into the refrigerator.
c) Arrow 1 points into the refrigerator and arrow 2 points into the refrigerator.
d) Arrow 1 points out of the refrigerator and arrow 2 points out of the refrigerator.
20.8.1. Which of the following properties applies to a microstate
exhibiting a high degree of entropy?
a) The microstate is at high temperature.
b) The microstate has a larger probability of being occupied than
other microstates.
c) The microstate is at low temperature.
d) The microstate is at high pressure.
e) The state is one with a larger number of microstates than other
states that have less entropy.
20.8.1. Which of the following properties applies to a microstate
exhibiting a high degree of entropy?
a) The microstate is at high temperature.
b) The microstate has a larger probability of being occupied than
other microstates.
c) The microstate is at low temperature.
d) The microstate is at high pressure.
e) The state is one with a larger number of microstates than other
states that have less entropy.
20.8.2. Consider the dice shown as a simple model of a thermodynamic system. In
this system, what corresponds to that microstates and what corresponds to the
macrostates?
a) The number on a die (e.g. 6 or 2) corresponds to a
microstate; and the numbers on all the dice (1, 2, 4, 6)
correspond to the macrostate.
b) The number on a die (e.g. 6 or 2) corresponds
to a microstate; and the sum of the numbers on all the dice
(1 + 2 + 4 + 6 = 13) corresponds to the macrostate.
c) The numbers on all the dice {1, 2, 4, 6} correspond to a microstate; and the sum
of the numbers on all the dice (1 + 2 + 4 + 6 = 13) corresponds to the macrostate.
d) The sum of the numbers on all the dice (1 + 2 + 4 + 6 = 13) corresponds to a
microstate; and the numbers on all the dice {1, 2, 4, 6} correspond to the macrostate.
20.8.2. Consider the dice shown as a simple model of a thermodynamic system. In
this system, what corresponds to that microstates and what corresponds to the
macrostates?
a) The number on a die (e.g. 6 or 2) corresponds to a
microstate; and the numbers on all the dice (1, 2, 4, 6)
correspond to the macrostate.
b) The number on a die (e.g. 6 or 2) corresponds
to a microstate; and the sum of the numbers on all the dice
(1 + 2 + 4 + 6 = 13) corresponds to the macrostate.
c) The numbers on all the dice {1, 2, 4, 6} correspond to a microstate; and the sum
of the numbers on all the dice (1 + 2 + 4 + 6 = 13) corresponds to the macrostate.
d) The sum of the numbers on all the dice (1 + 2 + 4 + 6 = 13) corresponds to a
microstate; and the numbers on all the dice {1, 2, 4, 6} correspond to the macrostate.
20.8.3. Consider the dice shown as a simple model of a thermodynamic system. In
this system, the numbers on all the dice {1, 2, 4, 6} correspond to a microstate;
and the sum of the numbers on all the dice
(1 + 2 + 4 + 6 = 13) corresponds to the macrostate.
Which one of the following microstates is
the least likely to occur?
a) {6, 1, 6, 1}
b) {1, 1, 1, 1}
c) {2, 5, 1, 4}
d) {2, 2, 4, 4}
e) All microstates are equally likely.
20.8.3. Consider the dice shown as a simple model of a thermodynamic system. In
this system, the numbers on all the dice {1, 2, 4, 6} correspond to a microstate;
and the sum of the numbers on all the dice
(1 + 2 + 4 + 6 = 13) corresponds to the macrostate.
Which one of the following microstates is
the least likely to occur?
a) {6, 1, 6, 1}
b) {1, 1, 1, 1}
c) {2, 5, 1, 4}
d) {2, 2, 4, 4}
e) All microstates are equally likely.
20.8.4. Consider the dice shown as a simple model of a thermodynamic system. In
this system, the numbers on all the dice {1, 2, 4, 6} correspond to a microstate;
and the sum of the numbers on all the dice
(1 + 2 + 4 + 6 = 13) corresponds to the macrostate.
Which one of the following macrostates is
the least likely to occur?
a) 4
b) 16
c) 10
d) 8
e) All macrostates are equally likely.
20.8.4. Consider the dice shown as a simple model of a thermodynamic system. In
this system, the numbers on all the dice {1, 2, 4, 6} correspond to a microstate;
and the sum of the numbers on all the dice
(1 + 2 + 4 + 6 = 13) corresponds to the macrostate.
Which one of the following macrostates is
the least likely to occur?
a) 4
b) 16
c) 10
d) 8
e) All macrostates are equally likely.