Contents
Preface xi
Acknowledgments xiii
Textbook Guide xv
0.1 List of Thermodynamics Textbooks by Discipline xv
0.2 Terminology and Notation Used in This Book xvi
0.3 Terminology and Notation Used in Textbooks xviii
1 About This Book 1
1.1 Who Should Use This Book? 2
1.2 Philosophy of This Book 3
1.3 Four Core Concepts of Thermodynamics 3
1.4 How to Use This Book 5
I Equilibrium
2 Philosophy of Thermodynamics 11
2.1 Thermodynamics 11
2.2 Scientific Models & Laws 12
2.3 Statistical Mechanics 14
3 Thermodynamic States, Variables & Quantities 17
3.1 Thermodynamic Variables & Quantities 17
3.2 More on Thermodynamic Quantities 19
3.3 Thermodynamic & Molecular States 20
4 Zeroth Law & Thermodynamic Equilibrium 23
4.1 Equation of State 23
4.2 Thermodynamic Equilibrium 26
4.3 Zeroth Law 27
4.4 Ideal Gases & Non-ideal Systems 29
II Energy
5 Molecular Energy, Internal Energy, & Temperature 33
5.1 Energy at the Molecular Scale 33
5.2 Internal Energy 35
5.3 Intermolecular Interactions & the Kinetic Model 37
5.4 Equipartition Theorem & Temperature 38
6 Boltzmann Distribution & the Kinetic Model 41
6.1 Boltzmann Distribution 41
6.2 Maxwell-Boltzmann Distribution 42
6.3 Maxwell Distribution of Speeds 44
III Thermodynamic Change
7 First Law & Thermodynamic Change 49
7.1 System & Surroundings 49
7.2 Thermodynamic Change 50
7.3 First Law 52
8 Work, Heat, & Reversible Change 55
8.1 State Functions & Path Functions 55
8.2 Definition of Work 57
8.3 Definition of Heat 59
8.4 Reversible & Irreversible Change 60
8.5 A Gas Expansion Example 62
9 Partial Derivative Quantities 65
9.1 Internal Energy & Heat Capacity at Constant Volume 66
9.2 Enthalpy & Heat Capacity at Constant Pressure 67
9.3 Other Partial Derivative Quantities 70
9.4 Partial Derivatives & Differentials 71
IV Entropy
10 Entropy & Information Theory 77
10.1 Why Does Entropy Seem So Complicated? 77
10.2 Entropy as Unknown Molecular Information 79
10.3 Amount of Information 80
10.4 Application to Thermodynamics 84
11 Entropy & Ideal Gas 87
11.1 Measuring Our Molecular Ignorance 87
11.2 Volume Contribution to Entropy 88
11.3 Temperature Contribution to Entropy 91
11.4 Combined Entropy Expression 92
11.5 Entropy, Heat, & Reversible Adiabatic Expansion 94
12 Second Law & Spontaneous Irreversible Change 97
12.1 Heat Engines & Thermodynamic Cycles 97
12.2 Traditional Statements of the Second Law 98
12.3 Entropy Statement of the Second Law 99
12.4 Information Statement of the Second Law 100
12.5 Maximum Entropy & the Clausius Inequality 103
13 Third Law, Carnot Cycle, & Absolute Entropy 107
13.1 Entropy & Reversible Change 107
13.2 Carnot Cycle & Absolute Zero Temperature 109
13.3 Third Law & Absolute Entropy 111
V FreeEnergy
14 Free Energy & Exergy 115
14.1 What Would Happen If Entropy Were a Variable? 116
14.2 Helmholtz and Gibbs Free Energies 117
14.3 Second Law & Maximum Work 119
14.4 Exergy 121
15 Chemical Potential, Fugacity, & Open Systems 123
15.1 What Would Happen If n Were a Variable? 123
15.2 Chemical Potential 125
15.3 Ideal Gas & Fugacity 126
VI Applications
16 Crazy Gay-Lussac’s Gas Expansion Emporium 131
16.1 Sales Pitch 131
16.2 How to Solve Gas Expansion Problems 132
16.3 Comprehensive Compendium 135
17 Electronic Emporium: Free Online Shopping! 139
VII Appendices
Appendix A: Beards Gone Wild! Facial Hair & the Founding Fathers of Thermodynamics 143
Appendix B: Thermodynamics, Abolitionism, & Sha Na Na 147
Appendix C: Thermodynamics & the Science of Steampunk 149
Steampunk Gallery 151
Travel Try Its 153
Photo Credits 155
Index 159
Preface
Thank you for your interest in A Conceptual Guide to Thermodynamics. This book is itself a new concept
of sorts, which merits some explanation.
First, a description of what this book is not. It is not a textbook; the discussion is insufficiently complete
to serve as the primary text for an undergraduate thermodynamics course, and there are no problems or
exercises. Neither is it a popular science or lay person’s introduction; the primary intended audience is
science and engineering students. Nor is it a history of thermodynamics; though that is itself a fascinating
subject, you will find little such discussion here. It is definitely not a book written to impress academic
colleagues; they will not be impressed.
What this book is is a conceptual and practical guide—a companion to your primary thermodynamics
textbook, meant to supplement and clarify the latter. The goal is to simultaneously improve both
your fundamental understanding of the material (the “conceptual” part) and your homework and exam
performance (the “practical” part), to better “get you through” your thermodynamics course. Culling
from over a decade of experience teaching undergraduate physical chemistry thermodynamics at Texas
Tech University, this book was written from top to bottom with the practical needs of you, the student,
foremost in mind.
But why should you buy this (fairly inexpensive) supplement in addition to the (no doubt much more
expensive) required textbook you have likely already purchased? There are several reasons. First, some
textbooks (and some lecturers) may give short shrift to the explication of core thermodynamics concepts
such as equilibrium and entropy. The likely reason is clear: there is much material to cover, and they do
not want to get bogged down in lengthy explanations and potentially confusing subtleties. Some of the
problems arising in this field are indeed profound and intractable; several of its brilliant but frustrated
early founders ended their own lives (see Appendix A)…That said, I have learned overmy years of teaching
thermodynamics that dedicating a modest amount of time during the early stages to a careful (but not
too rigorous) discussion of the key concepts—if done succinctly and clearly—can lead to major practical
benefits for students later on.
Second, a principal advantage of this approach is that the core concepts are prettymuch the same across
all of the many disciplines that (with good reason!) require thermodynamics training as part of their degree
plans. Thus, students of chemistry, physics, biology, geosciences, and the engineering fields, may all benefit
from this book, even though the application of this fundamental science varies greatly from field to field.
To this end, discipline-specific material is mostly avoided here, in favor of instruction designed to convey
the general logic of how to solve thermodynamics problems. In this context, memorization per se does
not really help so much, though many students are naturally inclined to fall back on this tried-and-true
companion. In contrast, a conceptual understanding offers something that most students ultimately find
to be far more valuable—a sense of howto approach any given problem, as opposed to that uncomfortable
state of having “no clue where to begin.”
Third, in its role as a true “supplement” to your primary textbook, this book provides explicit references
to the latest editions of all of the major thermodynamics texts used by each of the various disciplines
listed above. A comprehensive list is provided on p. xv of this book, in the Textbook Guide section. In
that section, also, terminology and notation differences between your primary text and this supplement
are “translated” for your convenience. Moreover, at the start of each chapter, you will find a map that
directs you to the page numbers in your primary text where corresponding material is presented. You will
also find the occasional textbook-specific commentary sprinkled throughout this book. All of this is to
make it as beneficial and easy for you to use as possible.
Among the range of individuals who would find this book useful, then, one might encounter:
a premed student preparing for the MCAT, for whom thermodynamics is the “hardest class they ever
took,” but who nevertheless needs a good MCAT score to get into medical school.
a brilliant physics major, who has no trouble solving problems, but is dissatisfied with vague unscientific
descriptions such as “entropy is a measure of disorder.”
a graduate or graduate-bound engineering student, keen on understanding what is really going on in
real-world applications.
a geochemist or materials scientist, seeking a better intuition about the role of free energy in amorphous
solids, or about processes that take place far from standard temperatures and pressures.
anyone else—student, teacher or research professional—whowould benefit froma better understanding
of this interesting subject.