Book contents
- Frontmatter
- Contents
- Preface
- 1 Orientation: what is physical chemistry about?
- Part One Quantum mechanics and spectroscopy
- Part Two Thermodynamics
- 4 Thermodynamics preliminaries
- 5 The First Law of Thermodynamics
- 6 The Second Law of Thermodynamics
- 7 Free energy
- 8 Chemical equilibrium and coupled reactions
- 9 Non-ideal behavior
- 10 Electrochemistry
- Part Three Kinetics
- Appendix A Standard thermodynamic properties at 298.15 K and 1 bar
- Appendix B Standard reduction potentials at 298.15 K and 1 bar
- Appendix C Physical properties of water
- Appendix D The SI system of units
- Appendix E Universal constants and conversion factors
- Appendix F Periodic table of the elements, with molar masses
- Appendix G Selected isotopic masses and abundances
- Appendix H Properties of exponentials and logarithmic functions
- Appendix I Review of integral calculus
- Appendix J End-of-term review problems
- Appendix K Answers to exercises
- Index
6 - The Second Law of Thermodynamics
from Part Two - Thermodynamics
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- 1 Orientation: what is physical chemistry about?
- Part One Quantum mechanics and spectroscopy
- Part Two Thermodynamics
- 4 Thermodynamics preliminaries
- 5 The First Law of Thermodynamics
- 6 The Second Law of Thermodynamics
- 7 Free energy
- 8 Chemical equilibrium and coupled reactions
- 9 Non-ideal behavior
- 10 Electrochemistry
- Part Three Kinetics
- Appendix A Standard thermodynamic properties at 298.15 K and 1 bar
- Appendix B Standard reduction potentials at 298.15 K and 1 bar
- Appendix C Physical properties of water
- Appendix D The SI system of units
- Appendix E Universal constants and conversion factors
- Appendix F Periodic table of the elements, with molar masses
- Appendix G Selected isotopic masses and abundances
- Appendix H Properties of exponentials and logarithmic functions
- Appendix I Review of integral calculus
- Appendix J End-of-term review problems
- Appendix K Answers to exercises
- Index
Summary
The First Law of Thermodynamics tells us that energy is conserved. The Second Law, which was originally formulated to help us understand steam engines, tells us that heat can't be converted into work with 100% efficiency. Our study of the Second Law will lead us to define a new state function known as the entropy. In turn, the entropy will turn out to be pivotal to our understanding of what drives chemical reactions.
The Second Law of Thermodynamics
There are many different statements of the Second Law. My favorite, because it seems to convey most clearly the meaning of this law, is due to Kelvin:
It is impossible for a system to undergo a cyclic process whose sole effects are the flow of an amount of heat from the surroundings to the system and the performance of an equal amount of work on the surroundings.
In more modern language, we might say that it is impossible to continuously convert heat completely into work. The Second Law limits the efficiency of heat engines, machines that convert heat into work. Just as the First Law makes a certain kind of perpetual motion machine impossible, the Second Law makes it impossible to build a so-called perpetual motion machine of the second kind, namely one that produces work from heat with perfect efficiency.
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- Chapter
- Information
- A Life Scientist's Guide to Physical Chemistry , pp. 109 - 140Publisher: Cambridge University PressPrint publication year: 2012