THERMODYNAMICS AND CHEMISTRY SECOND EDITION HOWARD DEVOE
Thermodynamics and Chemistry Second Edition Version 7a, December 2015 Howard DeVoe Associate Professor of Chemistry Emeritus University of Maryland, College Park, Maryland
The first edition of this book was previously published by Pearson Education, Inc. It was copyright 2001 by Prentice-Hall, Inc. The second edition, version 7a is copyright 2015 by Howard DeVoe. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs License, whose full text is at http://creativecommons.org/licenses/by-nc-nd/3.0 You are free to read, store, copy and print the PDF file for personal use. You are not allowed to alter, transform, or build upon this work, or to sell it or use it for any commercial purpose whatsoever, without the written consent of the copyright holder. The book was typeset using the LATEX typesetting system and the memoir class. Most of the figures were produced with PSTricks, a related software program. The fonts are Adobe Times, MathTime, Helvetica, and Computer Modern Typewriter. I thank the Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland (http://www.chem.umd.edu) for hosting the Web site for this book. The most recent version can always be found online at http://www.chem.umd.edu/thermobook If you are a faculty member of a chemistry or related department of a college or university, you may send a request to hdevoe@umd.edu for a complete Solutions Manual in PDF format for your personal use. In order to protect the integrity of the solutions, requests will be subject to verification of your faculty status and your agreement not to reproduce or transmit the manual in any form.
SHORT CONTENTS Biographical Sketches 15 Preface to the Second Edition 16 From the Preface to the First Edition 17 1 Introduction 19 2 Systems and Their Properties 27 3 The First Law 56 4 The Second Law 101 5 Thermodynamic Potentials 134 6 The Third Law and Cryogenics 149 7 Pure Substances in Single Phases 163 8 Phase Transitions and Equilibria of Pure Substances 192 9 Mixtures 222 10 Electrolyte Solutions 285 11 Reactions and Other Chemical Processes 302 12 Equilibrium Conditions in Multicomponent Systems 366 13 The Phase Rule and Phase Diagrams 418 14 Galvanic Cells 449 Appendix A Definitions of the SI Base Units 470 4
SHORT CONTENTS 5 Appendix B Physical Constants 471 Appendix C Symbols for Physical Quantities 472 Appendix D Miscellaneous Abbreviations and Symbols 476 Appendix E Calculus Review 479 Appendix F Mathematical Properties of State Functions 481 Appendix G Forces, Energy, and Work 486 Appendix H Standard Molar Thermodynamic Properties 504 Appendix I Answers to Selected Problems 507 Bibliography 511 Index 520 Thermodynamics and Chemistry, 2nd edition, version 7a 2015 by Howard DeVoe. Latest version: www.chem.umd.edu/thermobook
CONTENTS Biographical Sketches 15 Preface to the Second Edition 16 From the Preface to the First Edition 17 1 Introduction 19 1.1 Units... 19 1.1.1 Amount of substance and amount... 21 1.2 Quantity Calculus... 22 1.3 Dimensional Analysis... 24 Problem... 26 2 Systems and Their Properties 27 2.1 The System, Surroundings, and Boundary... 27 2.1.1 Extensive and intensive properties... 28 2.2 Phases and Physical States of Matter... 30 2.2.1 Physical states of matter... 30 2.2.2 Phase coexistence and phase transitions... 31 2.2.3 Fluids... 32 2.2.4 The equation of state of a fluid... 33 2.2.5 Virial equations of state for pure gases... 34 2.2.6 Solids... 36 2.3 Some Basic Properties and Their Measurement... 36 2.3.1 Mass... 36 2.3.2 Volume... 37 2.3.3 Density... 38 2.3.4 Pressure... 38 2.3.5 Temperature... 40 2.4 The State of the System... 45 2.4.1 State functions and independent variables... 45 2.4.2 An example: state functions of a mixture... 46 2.4.3 More about independent variables... 47 6
CONTENTS 7 2.4.4 Equilibrium states... 48 2.4.5 Steady states... 50 2.5 Processes and Paths... 50 2.6 The Energy of the System... 52 2.6.1 Energy and reference frames... 53 2.6.2 Internal energy... 53 Problems... 55 3 The First Law 56 3.1 Heat, Work, and the First Law... 56 3.1.1 The concept of thermodynamic work... 57 3.1.2 Work coefficients and work coordinates... 59 3.1.3 Heat and work as path functions... 60 3.1.4 Heat and heating... 61 3.1.5 Heat capacity... 62 3.1.6 Thermal energy... 62 3.2 Spontaneous, Reversible, and Irreversible Processes... 62 3.2.1 Reversible processes... 62 3.2.2 Irreversible processes... 66 3.2.3 Purely mechanical processes... 66 3.3 Heat Transfer... 67 3.3.1 Heating and cooling... 67 3.3.2 Spontaneous phase transitions... 68 3.4 Deformation Work... 69 3.4.1 Gas in a cylinder-and-piston device... 69 3.4.2 Expansion work of a gas... 71 3.4.3 Expansion work of an isotropic phase... 73 3.4.4 Generalities... 74 3.5 Applications of Expansion Work... 74 3.5.1 The internal energy of an ideal gas... 74 3.5.2 Reversible isothermal expansion of an ideal gas... 75 3.5.3 Reversible adiabatic expansion of an ideal gas... 75 3.5.4 Indicator diagrams... 77 3.5.5 Spontaneous adiabatic expansion or compression... 78 3.5.6 Free expansion of a gas into a vacuum... 79 3.6 Work in a Gravitational Field... 79 3.7 Shaft Work... 81 3.7.1 Stirring work... 83 3.7.2 The Joule paddle wheel... 84 3.8 Electrical Work... 86 3.8.1 Electrical work in a circuit... 86 3.8.2 Electrical heating... 88 3.8.3 Electrical work with a galvanic cell... 89 3.9 Irreversible Work and Internal Friction... 91 3.10 Reversible and Irreversible Processes: Generalities... 94 Problems... 96 Thermodynamics and Chemistry, 2nd edition, version 7a 2015 by Howard DeVoe. Latest version: www.chem.umd.edu/thermobook
CONTENTS 8 4 The Second Law 101 4.1 Types of Processes...101 4.2 Statements of the Second Law...102 4.3 Concepts Developed with Carnot Engines...105 4.3.1 Carnot engines and Carnot cycles...105 4.3.2 The equivalence of the Clausius and Kelvin Planck statements... 108 4.3.3 The efficiency of a Carnot engine...110 4.3.4 Thermodynamic temperature...113 4.4 Derivation of the Mathematical Statement of the Second Law...115 4.4.1 The existence of the entropy function...115 4.4.2 Using reversible processes to define the entropy...119 4.4.3 Some properties of the entropy...122 4.5 Irreversible Processes...123 4.5.1 Irreversible adiabatic processes...123 4.5.2 Irreversible processes in general...124 4.6 Applications...125 4.6.1 Reversible heating...126 4.6.2 Reversible expansion of an ideal gas...126 4.6.3 Spontaneous changes in an isolated system...127 4.6.4 Internal heat flow in an isolated system...127 4.6.5 Free expansion of a gas...128 4.6.6 Adiabatic process with work...128 4.7 Summary...129 4.8 The Statistical Interpretation of Entropy...129 Problems...132 5 Thermodynamic Potentials 134 5.1 Total Differential of a Dependent Variable...134 5.2 Total Differential of the Internal Energy...135 5.3 Enthalpy, Helmholtz Energy, and Gibbs Energy...137 5.4 Closed Systems...139 5.5 Open Systems...141 5.6 Expressions for Heat Capacity...142 5.7 Surface Work...143 5.8 Criteria for Spontaneity...144 Problems...147 6 The Third Law and Cryogenics 149 6.1 The Zero of Entropy...149 6.2 Molar Entropies...151 6.2.1 Third-law molar entropies...151 6.2.2 Molar entropies from spectroscopic measurements...154 6.2.3 Residual entropy...155 6.3 Cryogenics...156 6.3.1 Joule Thomson expansion...156 6.3.2 Magnetization...158 Thermodynamics and Chemistry, 2nd edition, version 7a 2015 by Howard DeVoe. Latest version: www.chem.umd.edu/thermobook
CONTENTS 9 Problem...162 7 Pure Substances in Single Phases 163 7.1 Volume Properties...163 7.2 Internal Pressure...165 7.3 Thermal Properties...167 7.3.1 The relation between C V;m and C p;m...167 7.3.2 The measurement of heat capacities...168 7.3.3 Typical values...173 7.4 Heating at Constant Volume or Pressure...174 7.5 Partial Derivatives with Respect to T, p, and V...176 7.5.1 Tables of partial derivatives...176 7.5.2 The Joule Thomson coefficient...179 7.6 Isothermal Pressure Changes...180 7.6.1 Ideal gases...180 7.6.2 Condensed phases...180 7.7 Standard States of Pure Substances...181 7.8 Chemical Potential and Fugacity...181 7.8.1 Gases...182 7.8.2 Liquids and solids...185 7.9 Standard Molar Quantities of a Gas...185 Problems...188 8 Phase Transitions and Equilibria of Pure Substances 192 8.1 Phase Equilibria...192 8.1.1 Equilibrium conditions...192 8.1.2 Equilibrium in a multiphase system...193 8.1.3 Simple derivation of equilibrium conditions...194 8.1.4 Tall column of gas in a gravitational field...195 8.1.5 The pressure in a liquid droplet...197 8.1.6 The number of independent variables...198 8.1.7 The Gibbs phase rule for a pure substance...199 8.2 Phase Diagrams of Pure Substances...199 8.2.1 Features of phase diagrams...200 8.2.2 Two-phase equilibrium...203 8.2.3 The critical point...205 8.2.4 The lever rule...206 8.2.5 Volume properties...209 8.3 Phase Transitions...211 8.3.1 Molar transition quantities...211 8.3.2 Calorimetric measurement of transition enthalpies...213 8.3.3 Standard molar transition quantities...213 8.4 Coexistence Curves...213 8.4.1 Chemical potential surfaces...214 8.4.2 The Clapeyron equation...215 8.4.3 The Clausius Clapeyron equation...218 Thermodynamics and Chemistry, 2nd edition, version 7a 2015 by Howard DeVoe. Latest version: www.chem.umd.edu/thermobook
CONTENTS 10 Problems...220 9 Mixtures 222 9.1 Composition Variables...222 9.1.1 Species and substances...222 9.1.2 Mixtures in general...222 9.1.3 Solutions...223 9.1.4 Binary solutions...224 9.1.5 The composition of a mixture...225 9.2 Partial Molar Quantities...225 9.2.1 Partial molar volume...226 9.2.2 The total differential of the volume in an open system...228 9.2.3 Evaluation of partial molar volumes in binary mixtures...230 9.2.4 General relations...232 9.2.5 Partial specific quantities...234 9.2.6 The chemical potential of a species in a mixture...235 9.2.7 Equilibrium conditions in a multiphase, multicomponent system.. 235 9.2.8 Relations involving partial molar quantities...237 9.3 Gas Mixtures...238 9.3.1 Partial pressure...239 9.3.2 The ideal gas mixture...239 9.3.3 Partial molar quantities in an ideal gas mixture...239 9.3.4 Real gas mixtures...242 9.4 Liquid and Solid Mixtures of Nonelectrolytes...245 9.4.1 Raoult s law...245 9.4.2 Ideal mixtures...247 9.4.3 Partial molar quantities in ideal mixtures...248 9.4.4 Henry s law...249 9.4.5 The ideal-dilute solution...252 9.4.6 Solvent behavior in the ideal-dilute solution...254 9.4.7 Partial molar quantities in an ideal-dilute solution...255 9.5 Activity Coefficients in Mixtures of Nonelectrolytes...257 9.5.1 Reference states and standard states...257 9.5.2 Ideal mixtures...258 9.5.3 Real mixtures...258 9.5.4 Nonideal dilute solutions...260 9.6 Evaluation of Activity Coefficients...261 9.6.1 Activity coefficients from gas fugacities...261 9.6.2 Activity coefficients from the Gibbs Duhem equation...264 9.6.3 Activity coefficients from osmotic coefficients...265 9.6.4 Fugacity measurements...267 9.7 Activity of an Uncharged Species...269 9.7.1 Standard states...269 9.7.2 Activities and composition...271 9.7.3 Pressure factors and pressure...272 9.8 Mixtures in Gravitational and Centrifugal Fields...274 Thermodynamics and Chemistry, 2nd edition, version 7a 2015 by Howard DeVoe. Latest version: www.chem.umd.edu/thermobook
CONTENTS 11 9.8.1 Gas mixture in a gravitational field...274 9.8.2 Liquid solution in a centrifuge cell...276 Problems...280 10 Electrolyte Solutions 285 10.1 Single-ion Quantities...286 10.2 Solution of a Symmetrical Electrolyte...288 10.3 Electrolytes in General...291 10.3.1 Solution of a single electrolyte...291 10.3.2 Multisolute solution...292 10.3.3 Incomplete dissociation...293 10.4 The Debye Hückel Theory...294 10.5 Derivation of the Debye Hückel Equation...297 10.6 Mean Ionic Activity Coefficients from Osmotic Coefficients...299 Problems...301 11 Reactions and Other Chemical Processes 302 11.1 Mixing Processes...302 11.1.1 Mixtures in general...303 11.1.2 Ideal mixtures...303 11.1.3 Excess quantities...305 11.1.4 The entropy change to form an ideal gas mixture...306 11.1.5 Molecular model of a liquid mixture...308 11.1.6 Phase separation of a liquid mixture...310 11.2 The Advancement and Molar Reaction Quantities...312 11.2.1 An example: ammonia synthesis...313 11.2.2 Molar reaction quantities in general...315 11.2.3 Standard molar reaction quantities...318 11.3 Molar Reaction Enthalpy...318 11.3.1 Molar reaction enthalpy and heat...318 11.3.2 Standard molar enthalpies of reaction and formation...319 11.3.3 Molar reaction heat capacity...322 11.3.4 Effect of temperature on reaction enthalpy...323 11.4 Enthalpies of Solution and Dilution...324 11.4.1 Molar enthalpy of solution...324 11.4.2 Enthalpy of dilution...326 11.4.3 Molar enthalpies of solute formation...327 11.4.4 Evaluation of relative partial molar enthalpies...328 11.5 Reaction Calorimetry...333 11.5.1 The constant-pressure reaction calorimeter...333 11.5.2 The bomb calorimeter...335 11.5.3 Other calorimeters...340 11.6 Adiabatic Flame Temperature...341 11.7 Gibbs Energy and Reaction Equilibrium...342 11.7.1 The molar reaction Gibbs energy...342 11.7.2 Spontaneity and reaction equilibrium...342 Thermodynamics and Chemistry, 2nd edition, version 7a 2015 by Howard DeVoe. Latest version: www.chem.umd.edu/thermobook
CONTENTS 12 11.7.3 General derivation...343 11.7.4 Pure phases...344 11.7.5 Reactions involving mixtures...344 11.7.6 Reaction in an ideal gas mixture...346 11.8 The Thermodynamic Equilibrium Constant...349 11.8.1 Activities and the definition of K...349 11.8.2 Reaction in a gas phase...352 11.8.3 Reaction in solution...353 11.8.4 Evaluation of K...354 11.9 Effects of Temperature and Pressure on Equilibrium Position...356 Problems...359 12 Equilibrium Conditions in Multicomponent Systems 366 12.1 Effects of Temperature...366 12.1.1 Variation of i =T with temperature...366 12.1.2 Variation of ı i =T with temperature...367 12.1.3 Variation of ln K with temperature...368 12.2 Solvent Chemical Potentials from Phase Equilibria...369 12.2.1 Freezing-point measurements...370 12.2.2 Osmotic-pressure measurements...372 12.3 Binary Mixture in Equilibrium with a Pure Phase...374 12.4 Colligative Properties of a Dilute Solution...375 12.4.1 Freezing-point depression...377 12.4.2 Boiling-point elevation...380 12.4.3 Vapor-pressure lowering...380 12.4.4 Osmotic pressure...381 12.5 Solid Liquid Equilibria...383 12.5.1 Freezing points of ideal binary liquid mixtures...383 12.5.2 Solubility of a solid nonelectrolyte...385 12.5.3 Ideal solubility of a solid...386 12.5.4 Solid compound of mixture components...386 12.5.5 Solubility of a solid electrolyte...389 12.6 Liquid Liquid Equilibria...391 12.6.1 Miscibility in binary liquid systems...391 12.6.2 Solubility of one liquid in another...391 12.6.3 Solute distribution between two partially-miscible solvents...394 12.7 Membrane Equilibria...394 12.7.1 Osmotic membrane equilibrium...395 12.7.2 Equilibrium dialysis...395 12.7.3 Donnan membrane equilibrium...396 12.8 Liquid Gas Equilibria...399 12.8.1 Effect of liquid pressure on gas fugacity...399 12.8.2 Effect of liquid composition on gas fugacities...400 12.8.3 The Duhem Margules equation...404 12.8.4 Gas solubility...405 12.8.5 Effect of temperature and pressure on Henry s law constants...407 Thermodynamics and Chemistry, 2nd edition, version 7a 2015 by Howard DeVoe. Latest version: www.chem.umd.edu/thermobook
CONTENTS 13 12.9 Reaction Equilibria...408 12.10 Evaluation of Standard Molar Quantities...410 Problems...412 13 The Phase Rule and Phase Diagrams 418 13.1 The Gibbs Phase Rule for Multicomponent Systems...418 13.1.1 Degrees of freedom...419 13.1.2 Species approach to the phase rule...419 13.1.3 Components approach to the phase rule...421 13.1.4 Examples...422 13.2 Phase Diagrams: Binary Systems...425 13.2.1 Generalities...425 13.2.2 Solid liquid systems...426 13.2.3 Partially-miscible liquids...430 13.2.4 Liquid gas systems with ideal liquid mixtures...431 13.2.5 Liquid gas systems with nonideal liquid mixtures...433 13.2.6 Solid gas systems...436 13.2.7 Systems at high pressure...439 13.3 Phase Diagrams: Ternary Systems...441 13.3.1 Three liquids...442 13.3.2 Two solids and a solvent...443 Problems...445 14 Galvanic Cells 449 14.1 Cell Diagrams and Cell Reactions...449 14.1.1 Elements of a galvanic cell...449 14.1.2 Cell diagrams...450 14.1.3 Electrode reactions and the cell reaction...451 14.1.4 Advancement and charge...451 14.2 Electric Potentials in the Cell...452 14.2.1 Cell potential...453 14.2.2 Measuring the equilibrium cell potential...454 14.2.3 Interfacial potential differences...455 14.3 Molar Reaction Quantities of the Cell Reaction...457 14.3.1 Relation between r G cell and E cell, eq...458 14.3.2 Relation between r G cell and r G...459 14.3.3 Standard molar reaction quantities...461 14.4 The Nernst Equation...462 14.5 Evaluation of the Standard Cell Potential...464 14.6 Standard Electrode Potentials...464 Problems...467 Appendix A Definitions of the SI Base Units 470 Appendix B Physical Constants 471 Thermodynamics and Chemistry, 2nd edition, version 7a 2015 by Howard DeVoe. Latest version: www.chem.umd.edu/thermobook
CONTENTS 14 Appendix C Symbols for Physical Quantities 472 Appendix D Miscellaneous Abbreviations and Symbols 476 D.1 Physical States...476 D.2 Subscripts for Chemical Processes...477 D.3 Superscripts...478 Appendix E Calculus Review 479 E.1 Derivatives...479 E.2 Partial Derivatives...479 E.3 Integrals...480 E.4 Line Integrals...480 Appendix F Mathematical Properties of State Functions 481 F.1 Differentials...481 F.2 Total Differential...481 F.3 Integration of a Total Differential...483 F.4 Legendre Transforms...484 Appendix G Forces, Energy, and Work 486 G.1 Forces between Particles...487 G.2 The System and Surroundings...490 G.3 System Energy Change...492 G.4 Macroscopic Work...493 G.5 The Work Done on the System and Surroundings......495 G.6 The Local Frame and Internal Energy...495 G.7 Nonrotating Local Frame...499 G.8 Center-of-mass Local Frame...499 G.9 Rotating Local Frame...502 G.10 Earth-Fixed Reference Frame...503 Appendix H Standard Molar Thermodynamic Properties 504 Appendix I Answers to Selected Problems 507 Bibliography 511 Index 520 Thermodynamics and Chemistry, 2nd edition, version 7a 2015 by Howard DeVoe. Latest version: www.chem.umd.edu/thermobook
BIOGRAPHICAL SKETCHES Benjamin Thompson, Count of Rumford... 63 James Prescott Joule... 85 Sadi Carnot...106 Rudolf Julius Emmanuel Clausius...109 William Thomson, Lord Kelvin...114 Max Karl Ernst Ludwig Planck...116 Josiah Willard Gibbs...138 Walther Hermann Nernst...150 William Francis Giauque...159 Benoit Paul Émile Clapeyron...217 William Henry...250 Gilbert Newton Lewis...270 Peter Josephus Wilhelmus Debye...295 Germain Henri Hess...321 François-Marie Raoult...379 Jacobus Henricus van t Hoff...382 15
PREFACE TO THE SECOND EDITION This second edition of Thermodynamics and Chemistry is a revised and enlarged version of the first edition published by Prentice Hall in 2001. The book is designed primarily as a textbook for a one-semester course for graduate or undergraduate students who have already been introduced to thermodynamics in a physical chemistry course. The PDF file of this book contains hyperlinks to pages, sections, equations, tables, figures, bibliography items, and problems. If you are viewing the PDF on a screen, the links are present, although they are not marked in any special way. If you click on a reference to a page number, equation number, and so on, it will take you to that location. Scattered through the text are sixteen one-page biographical sketches of some of the historical giants of thermodynamics. A list is given on the preceding page. The sketches are not intended to be comprehensive biographies, but rather to illustrate the human side of thermodynamics the struggles and controversies by which the concepts and experimental methodology of the subject were developed. The epigraphs on page 18 are intended to suggest the nature and importance of classical thermodynamics. You may wonder about the conversation between Alice and Humpty Dumpty. Its point, particularly important in the study of thermodynamics, is the need to pay attention to definitions the intended meanings of words. I welcome comments and suggestions for improving this book. My e-mail address appears below. Howard DeVoe hdevoe@umd.edu 16
FROM THE PREFACE TO THE FIRST EDITION Classical thermodynamics, the subject of this book, is concerned with macroscopic aspects of the interaction of matter with energy in its various forms. This book is designed as a text for a onesemester course for senior undergraduate or graduate students who have already been introduced to thermodynamics in an undergraduate physical chemistry course. Anyone who studies and uses thermodynamics knows that a deep understanding of this subject does not come easily. There are subtleties and interconnections that are difficult to grasp at first. The more times one goes through a thermodynamics course (as a student or a teacher), the more insight one gains. Thus, this text will reinforce and extend the knowledge gained from an earlier exposure to thermodynamics. To this end, there is fairly intense discussion of some basic topics, such as the nature of spontaneous and reversible processes, and inclusion of a number of advanced topics, such as the reduction of bomb calorimetry measurements to standard-state conditions. This book makes no claim to be an exhaustive treatment of thermodynamics. It concentrates on derivations of fundamental relations starting with the thermodynamic laws and on applications of these relations in various areas of interest to chemists. Although classical thermodynamics treats matter from a purely macroscopic viewpoint, the book discusses connections with molecular properties when appropriate. In deriving equations, I have strived for rigor, clarity, and a minimum of mathematical complexity. I have attempted to clearly state the conditions under which each theoretical relation is valid because only by understanding the assumptions and limitations of a derivation can one know when to use the relation and how to adapt it for special purposes. I have taken care to be consistent in the use of symbols for physical properties. The choice of symbols follows the current recommendations of the International Union of Pure and Applied Chemistry (IUPAC) with a few exceptions made to avoid ambiguity. I owe much to J. Arthur Campbell, Luke E. Steiner, and William Moffitt, gifted teachers who introduced me to the elegant logic and practical utility of thermodynamics. I am immensely grateful to my wife Stephanie for her continued encouragement and patience during the period this book went from concept to reality. I would also like to acknowledge the help of the following reviewers: James L. Copeland, Kansas State University; Lee Hansen, Brigham Young University; Reed Howald, Montana State University Bozeman; David W. Larsen, University of Missouri St. Louis; Mark Ondrias, University of New Mexico; Philip H. Rieger, Brown University; Leslie Schwartz, St. John Fisher College; Allan L. Smith, Drexel University; and Paul E. Smith, Kansas State University. 17
A theory is the more impressive the greater the simplicity of its premises is, the more different kinds of things it relates, and the more extended is its area of applicability. Therefore the deep impression which classical thermodynamics made upon me. It is the only physical theory of universal content concerning which I am convinced that, within the framework of the applicability of its basic concepts, it will never be overthrown. Albert Einstein Thermodynamics is a discipline that involves a formalization of a large number of intuitive concepts derived from common experience. J. G. Kirkwood and I. Oppenheim, Chemical Thermodynamics, 1961 The first law of thermodynamics is nothing more than the principle of the conservation of energy applied to phenomena involving the production or absorption of heat. Max Planck, Treatise on Thermodynamics, 1922 The law that entropy always increases the second law of thermodynamics holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell s equations then so much the worse for Maxwell s equations. If it is found to be contradicted by observation well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation. Sir Arthur Eddington, The Nature of the Physical World, 1928 Thermodynamics is a collection of useful relations between quantities, every one of which is independently measurable. What do such relations tell one about one s system, or in other words what do we learn from thermodynamics about the microscopic explanations of macroscopic changes? Nothing whatever. What then is the use of thermodynamics? Thermodynamics is useful precisely because some quantities are easier to measure than others, and that is all. M. L. McGlashan, J. Chem. Educ., 43, 226 232 (1966) When I use a word, Humpty Dumpty said, in rather a scornful tone, it means just what I choose it to mean neither more nor less. The question is, said Alice, whether you can make words mean so many different things. The question is, said Humpty Dumpty, which is to be master that s all. Lewis Carroll, Through the Looking-Glass