• Home
  • Textbooks
  • Conceptual Physics
  • Thermodynamics

Conceptual Physics

Paul G. Hewitt

Chapter 18

Thermodynamics - all with Video Answers

Educators

+ 4 more educators

Chapter Questions

00:32

Problem 1

What is the origin and meaning of the word thermodynamics?

Averell Hause
Averell Hause
Carnegie Mellon University
01:29

Problem 2

Why do early thermodynamic models invoke macroscopic notions like mechanical work, pressure, and temperature?

Shital Rijal
Shital Rijal
Numerade Educator
01:36

Problem 3

By how much does the volume of gas at $0^{\circ} \mathrm{C}$ contract for each decrease in temperature of 1 Celsius degree when the pressure is held constant?

Averell Hause
Averell Hause
Carnegie Mellon University
02:33

Problem 4

By how much does the pressure of gas at $0^{\circ} \mathrm{C}$ decrease for each decrease in temperature of 1 Celsius degree when the volume is held constant?

Shital Rijal
Shital Rijal
Numerade Educator
01:10

Problem 5

Why is it not possible to cool a gas at $0^{\circ} \mathrm{C}$ by more than $273^{\circ} \mathrm{C}$ if the pressure of the gas is held constant?

Averell Hause
Averell Hause
Carnegie Mellon University
01:41

Problem 6

What happens to the kinetic energy of atoms and molecules at a temperature of absolute zero?

Shital Rijal
Shital Rijal
Numerade Educator
01:32

Problem 7

Is the principal concern in the study of thermodynamics the amount of internal energy in a system or the changes in internal energy in a substance?

Averell Hause
Averell Hause
Carnegie Mellon University
02:58

Problem 8

What form of energy needs to be included in the law of conservation of energy to lead to the first law of
thermodynamics?

Shital Rijal
Shital Rijal
Numerade Educator
01:58

Problem 9

How does a system use added heat?

Averell Hause
Averell Hause
Carnegie Mellon University
01:39

Problem 10

What is the relationship among heat added to a system, change in the system’s internal energy, and external work done by the system?

Shital Rijal
Shital Rijal
Numerade Educator
01:21

Problem 11

What happens to the internal energy of a system when mechanical work is done on it? What happens to its temperature?

Averell Hause
Averell Hause
Carnegie Mellon University
01:40

Problem 12

How are adiabatic conditions achieved in a system?

Shital Rijal
Shital Rijal
Numerade Educator
01:33

Problem 13

If work is done on a system, does the internal energy of the system increase or decrease? If work is done by a system, does the internal energy of the system increase or decrease?

Averell Hause
Averell Hause
Carnegie Mellon University
02:15

Problem 14

What happens to air temperature as pressure increases?

Shital Rijal
Shital Rijal
Numerade Educator
01:13

Problem 15

What is the adiabatic form of the first law?

Averell Hause
Averell Hause
Carnegie Mellon University
00:57

Problem 16

What generally happens to the temperature of rising air? Of sinking air?

Shital Rijal
Shital Rijal
Numerade Educator
01:41

Problem 17

When does temperature inversion take place?

Averell Hause
Averell Hause
Carnegie Mellon University
01:35

Problem 18

Do adiabatic processes apply only to gases? Defend your answer.

Shital Rijal
Shital Rijal
Numerade Educator
03:19

Problem 19

Can a heat engine convert all the heat energy supplied to it into mechanical energy?

Averell Hause
Averell Hause
Carnegie Mellon University
02:32

Problem 20

What role does the ‘reservoir’ have in a heat engine?

Shital Rijal
Shital Rijal
Numerade Educator
02:03

Problem 21

What exactly is thermal pollution?

Averell Hause
Averell Hause
Carnegie Mellon University
02:21

Problem 22

How does the second law relate to heat engines?

Shital Rijal
Shital Rijal
Numerade Educator
01:36

Problem 23

Why is the condensation part of the cycle in a steam turbine so essential?

Averell Hause
Averell Hause
Carnegie Mellon University
02:37

Problem 24

Distinguish between high-quality energy and low-quality energy in terms of organized and disorganized energy. Give an example of each.

Shital Rijal
Shital Rijal
Numerade Educator
03:50

Problem 25

What happens to the quality of energy with each transformation? What does the word ‘quality’ imply?

Averell Hause
Averell Hause
Carnegie Mellon University
02:09

Problem 26

With respect to orderly and disorderly states, what do natural systems tend to do? Can a disorderly state ever transform into an orderly state? Explain.

Shital Rijal
Shital Rijal
Numerade Educator
01:00

Problem 27

How does the entropy in a system change with the passage of time?

Averell Hause
Averell Hause
Carnegie Mellon University
01:51

Problem 28

Distinguish between the first and second laws of thermodynamics in terms of whether or not exceptions occur.

Shital Rijal
Shital Rijal
Numerade Educator
01:08

Problem 29

Which law forbids the attainment of the temperature of absolute zero?

Averell Hause
Averell Hause
Carnegie Mellon University
01:49

Problem 30

What is the zeroth law of thermodynamics?

Shital Rijal
Shital Rijal
Numerade Educator
01:46

Problem 31

Perform the activity in the Thermodynamics Dramatized! box. And show that the pan of water does not
have to be cold for the can to collapse. Try warm (but not boiling) water and you’ll see collapse. Impress your friends with this one!

Anatole Borisov
Anatole Borisov
Numerade Educator
01:44

Problem 32

With a hammer, pound a nail into a piece of wood. Withdraw the nail quickly and feel its warmth! Think
and Solve #41 takes this further!

Shital Rijal
Shital Rijal
Numerade Educator
01:18

Problem 33

Show that the ideal efficiency is 90% for an engine in which fuel is heated to 3000 K and the surrounding air is 300 K.

Prabhu Ramji
Prabhu Ramji
Numerade Educator
01:32

Problem 34

The ideal efficiency of an engine is 80%. Calculate the temperature of the surrounding air if its fuel is heated to 3000 K.

Shital Rijal
Shital Rijal
Numerade Educator
01:44

Problem 35

What is the ideal efficiency of an automobile engine that operates between the temperatures $600^{\circ} \mathrm{C}$ and $320^{\circ} \mathrm{C}$ ? (Why is your answer not 47$\%$ ?)

Averell Hause
Averell Hause
Carnegie Mellon University
01:38

Problem 36

Consider an ocean thermal energy conversion (OTEC) power plant that operates on a temperature difference between deep $4^{\circ} \mathrm{C}$ water and $25^{\circ} \mathrm{C}$ surface water. Show
that the Carnot efficiency of this plant is 7$\%$

Shital Rijal
Shital Rijal
Numerade Educator
02:22

Problem 37

On a chilly $10^{\circ} \mathrm{C}$ day, your friend who loves cold weather says she wishes it were twice as cold. Taking this literally, show that the temperature she wishes for would be $-131.5^{\circ} \mathrm{C} .$

Averell Hause
Averell Hause
Carnegie Mellon University
03:36

Problem 38

Imagine a giant dry-cleaner's bag full of air at a tem- perature of $-35^{\circ} \mathrm{C}$ floating like a balloon with a string hanging from it 10 $\mathrm{km}$ above the ground. Estimate what its temperature would be if you were able to yank it suddenly back to Earth's surface.

Shital Rijal
Shital Rijal
Numerade Educator
01:39

Problem 39

Wally Whacko claims to have invented a heat engine that will revolutionize industry. It runs between a hot source at $300^{\circ} \mathrm{C}$ and a cold $\sin \mathrm{k}$ at $25^{\circ} \mathrm{C}$ . He claims that his engine is 92$\%$ efficient.
a. What error did he make in his choice of temperature scales?
b. What is the actual maximum efficiency of his engine?

Averell Hause
Averell Hause
Carnegie Mellon University
02:57

Problem 40

A power station with an efficiency of 0.4 generates $10^{8} \mathrm{W}$ of electric power and dissipates $1.5 \times 10^{8} \mathrm{J}$ of heat energy each second to the cooling water that flows through it, which increases its temperature by 3 Celsius degrees. Knowing that the specific heat of water in SI units is $4184 \mathrm{J} / \mathrm{kg} \cdot^{\circ} \mathrm{C},$ show that $12,000 \mathrm{kg}$ of warmed water flows through the plant each second.

Shital Rijal
Shital Rijal
Numerade Educator
01:45

Problem 41

Consider a 6.0 -g steel nail 8.0 $\mathrm{cm}$ long and a hammer that exerts an average force of 600 $\mathrm{N}$ on the nail when it is being driven into a piece of wood. The nail becomes warmer. Show that the increase in the nail's temperature is $17.8^{\circ} \mathrm{C}$ . (Assume that the specific heat capacity of steel is 450 $\mathrm{J} / \mathrm{kg} \cdot$ C..

Averell Hause
Averell Hause
Carnegie Mellon University
08:07

Problem 42

Construct a table of all the possible combinations of numbers that can come up when you throw two dice. Your friend says, Yes, I know that 7 is the most likely total number when two dice are thrown. But why 7$?^{\prime \prime}$ Based on your table, answer your friend, and explain that, in thermodynamics, the situations that are likely to be observed are those that can be formed in the greatest number of ways.

Shital Rijal
Shital Rijal
Numerade Educator
01:23

Problem 43

A friend said the temperature inside a particular oven is 500 and the temperature inside a particular star is 50,000. You’re unsure whether your friend meant Celsius degrees or kelvins. How much difference does it make in each case?

Averell Hause
Averell Hause
Carnegie Mellon University
02:19

Problem 44

The temperature of the Sun's interior is about $10^{7}$ degrees. Does it matter whether this is degrees Celsius or kelvins? Explain.

Shital Rijal
Shital Rijal
Numerade Educator
01:58

Problem 45

When heat flows from a warm object in contact with a cool object, do both objects undergo the same amount of temperature change?

Averell Hause
Averell Hause
Carnegie Mellon University
01:18

Problem 46

Consider a jar of helium with a temperature of $0^{\circ} \mathrm{C}$ . What will its temperature be if it is twice as hot (has twice the internal energy)?

Shital Rijal
Shital Rijal
Numerade Educator
01:34

Problem 47

If you vigorously shake a can of chicken broth for more than a minute, will the temperature of the broth
increase? (Try it and see.)

Averell Hause
Averell Hause
Carnegie Mellon University
03:23

Problem 48

Why does a bicycle pump get warm when the air inside it is compressed?

Shital Rijal
Shital Rijal
Numerade Educator
00:54

Problem 49

Suppose you do 100 J of work in compressing a gas. If 80 J of heat escapes in the process, what is the change in the internal energy of the gas?

Averell Hause
Averell Hause
Carnegie Mellon University
04:44

Problem 50

Why does the bottom of a tire pump feel hot when you pump air in the tire, but when air is released, the valve stem feels cool?

Shital Rijal
Shital Rijal
Numerade Educator
01:28

Problem 51

When you blow up a balloon, do you slightly warm the balloon? When air is allowed to rush out of it, how, if at all, does the temperature of that expanding air change?

Averell Hause
Averell Hause
Carnegie Mellon University
02:00

Problem 52

What happens to the gas pressure in a sealed gallon can when it is heated? When it is cooled? Why?

Shital Rijal
Shital Rijal
Numerade Educator
00:57

Problem 53

Why does cold mountain air become warm when it descends into a valley?

Averell Hause
Averell Hause
Carnegie Mellon University
03:29

Problem 54

What is the ultimate source of energy in coal, oil, and wood? Why do we call energy from wood renewable but energy from coal and oil nonrenewable?

Shital Rijal
Shital Rijal
Numerade Educator
01:03

Problem 55

What is the ultimate source of energy in a hydroelectric power plant?

Averell Hause
Averell Hause
Carnegie Mellon University
02:35

Problem 56

Why is it advantageous to use steam that is as hot as possible in a steam-driven turbine?

Shital Rijal
Shital Rijal
Numerade Educator
01:17

Problem 57

How does the ideal efficiency of an automobile relate to the temperature of the engine and the temperature of the environment in which it operates? Be specific.

Averell Hause
Averell Hause
Carnegie Mellon University
01:47

Problem 58

What happens to the efficiency of a heat engine when the temperature of the reservoir into which thermal energy is transferred is lowered?

Shital Rijal
Shital Rijal
Numerade Educator
02:14

Problem 59

What do you understand by an ideal efficiency of zero?

Averell Hause
Averell Hause
Carnegie Mellon University
03:47

Problem 60

To increase the efficiency of a heat engine, would it be preferable to produce the same temperature increment by increasing the temperature of the reservoir while maintaining the temperature of the sink constant, or to decrease the temperature of the sink while maintaining the temperature of the reservoir constant? Explain.

Shital Rijal
Shital Rijal
Numerade Educator
02:30

Problem 61

Could you cool a kitchen by leaving the refrigerator door open and closing the kitchen door and windows? Explain.

Averell Hause
Averell Hause
Carnegie Mellon University
01:32

Problem 62

Could you warm a kitchen by leaving the door of a hot oven open? Explain.

Shital Rijal
Shital Rijal
Numerade Educator
02:28

Problem 63

An electric fan not only doesn’t decrease the temperature of air but actually increases the air temperature. How, then, are you cooled by a fan on a hot day?

Averell Hause
Averell Hause
Carnegie Mellon University
03:42

Problem 64

Strictly speaking, why will a refrigerator that contains a fixed amount of food consume more energy in a warm room than in a cold room?

Shital Rijal
Shital Rijal
Numerade Educator
01:09

Problem 65

A refrigerator moves heat from cold to warm. Why doesn’t this violate the second law of thermodynamics?

Averell Hause
Averell Hause
Carnegie Mellon University
02:09

Problem 66

What happens to the density of a quantity of gas when its temperature is decreased and its pressure is held constant?

Shital Rijal
Shital Rijal
Numerade Educator
00:59

Problem 67

If you squeeze an air-filled balloon and no heat escapes, what happens to the internal energy of the gas in the balloon?

Averell Hause
Averell Hause
Carnegie Mellon University
05:28

Problem 68

In buildings that are being electrically heated, is it at all wasteful to turn all the lights on? Is turning all the lights on wasteful if the building is being cooled by air conditioning?

Shital Rijal
Shital Rijal
Numerade Educator
01:42

Problem 69

Why can the drinking bird in Figure 17.4 in Chapter 17 be considered a heat engine?

Averell Hause
Averell Hause
Carnegie Mellon University
03:32

Problem 70

Molecules in the combustion chamber of a rocket engine are in a high state of random motion. When the molecules are expelled through a nozzle in a more ordered state, will their temperature be higher than, lower than, or the same as their initial temperature in the chamber before being exhausted?

Shital Rijal
Shital Rijal
Numerade Educator
03:55

Problem 71

Is the total energy of the universe becoming more unavailable with time? Explain.

Averell Hause
Averell Hause
Carnegie Mellon University
02:52

Problem 72

According to the second law of thermodynamics, is the universe moving to a more ordered state or to a more disordered state?

Shital Rijal
Shital Rijal
Numerade Educator
04:05

Problem 73

How does temperature inversion in the atmosphere 73become visible when air is invisible?

Averell Hause
Averell Hause
Carnegie Mellon University
04:13

Problem 74

The ocean possesses enormous numbers of molecules, all with kinetic energy. Can this energy be extracted and used as a power source? Defend your answer.

Yaqub Khan
Yaqub Khan
Numerade Educator
03:27

Problem 75

Why do we say a substance in a liquid phase is more dis-ordered than the same substance in a solid phase?

Averell Hause
Averell Hause
Carnegie Mellon University
01:47

Problem 76

Water evaporates from a salt solution and leaves behind salt crystals that have a higher degree of molecular order than the more randomly moving molecules in the salt- water. Has the entropy principle been violated? Why or why not?

Matthew Miranda
Matthew Miranda
Numerade Educator
02:44

Problem 77

Water put into the freezer compartment of your refrigerator goes to a state of less molecular disorder when it freezes. Is this an exception to the entropy principle? Explain.

Averell Hause
Averell Hause
Carnegie Mellon University
01:06

Problem 78

As a chicken develops from an egg, it becomes more ordered with time. Does this violate the principle of
entropy? Explain.

Keshav Singh
Keshav Singh
Numerade Educator
02:47

Problem 79

The United States Patent and Trademark Office rejects claims for perpetual motion machines (in which energy output is as great as or greater than energy input) without even investigating them. Why is this?

Averell Hause
Averell Hause
Carnegie Mellon University
02:51

Problem 80

Discuss whether or not it is possible to wholly convert a given amount of mechanical energy into thermal energy. Is it possible to wholly convert a given amount of thermal energy into mechanical energy? Cite examples to illustrate your answers.

William Dunkerton
William Dunkerton
Numerade Educator
03:45

Problem 81

Heat always flows spontaneously from an object with a higher temperature to an object with a lower temperature. Is this the same as saying that heat always flows from an object with greater internal energy to one with less internal energy? Discuss why or why not.

Averell Hause
Averell Hause
Carnegie Mellon University
02:55

Problem 82

Everybody knows that warm air rises. So it might seem that the air temperature should be higher at the tops of mountains than down below. Discuss why the opposite is most often the case.

Km Neeraj
Km Neeraj
Numerade Educator
01:47

Problem 83

Hovering over the surface of our skin is a layer of air some 3 millimeters in thickness that acts as a thermal blanket. On a hot day, what effect does a breeze on bare skin have on your skin? What effect does it have on a cold day?

Averell Hause
Averell Hause
Carnegie Mellon University
03:59

Problem 84

Your heart is a pump that supplies blood to all parts of your body, including your brain. Particle motion in the brain, like in any device, generates heat. What does this suggest about the temperatures of the blood entering your brain and the blood leaving your brain (and why might this affect concentration)?

Prashant Bana
Prashant Bana
Numerade Educator
01:34

Problem 85

The temperature in Boston was $40^{\circ} \mathrm{F}$ when it was $80^{\circ} \mathrm{F}$ in St. Petersburg, FL. What is your response to a friend who suggests that it was twice as hot in St. Petersburg on that day?

Averell Hause
Averell Hause
Carnegie Mellon University
02:54

Problem 86

The combined molecular kinetic energies of molecules in a cool lake are greater than the combined molecular kinetic energies of molecules in a cup of hot tea. Pretend you partially immerse the teacup in the lake and the tea absorbs 10 calories from the water and becomes hotter, while the water that gives up 10 calories becomes cooler. Would this energy transfer violate the first law of thermodynamics? The second law of thermodynamics? Discuss your answers.

Km Neeraj
Km Neeraj
Numerade Educator
01:33

Problem 87

Why is thermal pollution a relative term?

Averell Hause
Averell Hause
Carnegie Mellon University
01:27

Problem 88

The Thermodynamics Dramatized! box shows the crushing of an inverted steam-filled can placed in a pan of water. Does the water need to be cold? Would crushing occur if the water were hot but not boiling? Would the can crush in boiling water? Discuss this, and then try it and see!

Manish Jain
Manish Jain
Numerade Educator
01:52

Problem 89

Defend the statement that 100% of the electric energy that goes into lighting a lamp is converted to thermal energy. Are the first and the second laws of thermodynamics violated?

Averell Hause
Averell Hause
Carnegie Mellon University
01:36

Problem 90

Discuss this statement: The second law of thermodynamics is one of the most fundamental laws of nature, yet it is not an exact law at all. Why not?

Km Neeraj
Km Neeraj
Numerade Educator
03:04

Problem 91

It is generally assumed that perpetual motion machines are impossible to construct. Is it inconsistent to say that molecules are in perpetual motion?

Averell Hause
Averell Hause
Carnegie Mellon University
03:04

Problem 92

A classmate says that all this stuff about no perpetual motion is bunk; that atoms, planets, stars, and everything are in perpetual motion. What distinction is being missed here?

Averell Hause
Averell Hause
Carnegie Mellon University
02:23

Problem 93

(a) If you spent 10 minutes repeatedly shaking and throwing down a pair of coins, would you expect to see two heads come up at least once? (b) If you spent an hour shaking a handful of 10 coins and throwing them down, would you expect to see all 10 come up heads at least once? (c) If you stirred a box of 10,000 coins and tossed them repeatedly on the floor all day long, would you expect to see all 10,000 appear as heads at least once? Discuss.

Averell Hause
Averell Hause
Carnegie Mellon University