Concepts in Thermal Physics

Citation

Blundell, S. J., & Blundell, K. M. (2010). Concepts in Thermal Physics (2nd ed.). Oxford University Press.

Chapter Summary

The book consists of 37 short chapters grouped into nine parts, followed by appendices (constants, useful formulae and mathematics, the electromagnetic spectrum, thermodynamic definitions and expansion formulae, reduced mass, a glossary of symbols) and a bibliography. A reviewer of the first edition noted that each chapter covers a single concept, and that every chapter ends with exercises.

Part I, Chapters 1–4: Introduction; Heat; Probability; Temperature and the Boltzmann factor

The opening part sets the scene and supplies the probability needed later. A chapter on probability comes before the one on temperature, which introduces the Boltzmann factor, so statistical ideas are in place before thermodynamics begins.

Part II, Chapters 5–8: The Maxwell–Boltzmann distribution; Pressure; Molecular effusion; The mean free path and collisions

Kinetic theory of gases, with the gas as the first physical system. According to the review of the first edition, the authors present this part as optional and postponable.

Part III, Chapters 9–10: Transport properties in gases; The thermal diffusion equation

Transport in gases and the diffusion equation for heat.

Parts IV–V, Chapters 11–15: Energy; Isothermal and adiabatic processes; Heat engines and the second law; Entropy; Information theory

The first law and the second law. The part on the second law ends with a chapter on information theory alongside entropy.

Part VI, Chapters 16–18: Thermodynamic potentials; Rods, bubbles and magnets; The third law

Thermodynamics "in action": thermodynamic potentials, then systems other than gases (rods, bubbles, magnets), and the third law.

Part VII, Chapters 19–24: Equipartition of energy; The partition function; Statistical mechanics of an ideal gas; The chemical potential; Photons; Phonons

Statistical mechanics proper begins here, after the laws of thermodynamics. The partition function is followed by the ideal gas, the chemical potential, and photons and phonons as gases of quanta.

Part VIII, Chapters 25–30: Relativistic gases; Real gases; Cooling real gases; Phase transitions; Bose–Einstein and Fermi–Dirac distributions; Quantum gases and condensates

Beyond the ideal classical gas: relativistic and real gases, their cooling, phase transitions, and the two quantum distributions with their applications to quantum gases and condensates.

Part IX, Chapters 31–37: Sound waves; Shock waves; Brownian motion and fluctuations; Non-equilibrium thermodynamics; Stars; Compact objects; Earth's atmosphere

Special topics. The publisher highlights applications to stellar astrophysics, condensed matter, information and climate; the last three chapters carry the ideas into stars, compact objects and the atmosphere.

Key Concepts

Parts I–III: Chapters 1–10

• Boltzmann factor: the probability weighting that links temperature to the distribution of energy among states.
• Maxwell–Boltzmann distribution: the distribution of molecular speeds in a gas.
• Mean free path: the typical distance a molecule travels between collisions, used for transport properties.
• Thermal diffusion equation: the equation governing how heat spreads through a material.

Parts IV–VI: Chapters 11–18

• First and second laws: energy conservation with heat and work, and the limits on heat engines.
• Entropy: the state function of the second law, discussed alongside information theory.
• Thermodynamic potentials: the functions used to treat systems at constant temperature, pressure or field.
• Third law: the behaviour of entropy as temperature approaches zero.

Parts VII–IX: Chapters 19–37

• Partition function: the central quantity of statistical mechanics, from which thermodynamic properties follow.
• Chemical potential: the quantity governing particle exchange between systems.
• Bose–Einstein and Fermi–Dirac distributions: the quantum statistics of identical particles.
• Phase transitions: changes of state, treated in Chapter 28.

Critical Analysis

Strengths

• Thermodynamics before statistical mechanics. The table of contents places the laws of thermodynamics (Parts IV–VI) before the partition function (Chapter 20). Narayan, reviewing the first edition in Physics Today (October 2007), regarded this as a good choice, because thermodynamics applies to complex systems without a statistical analysis and its generality should not be lost.
• Short, single-concept chapters. The review stresses that the 37 chapters are short and that the presentation is, in general, remarkably clear. Short chapters also make it easy to assign selected parts.
• Gases first, data in the figures. The reviewer liked that the first physical system is a gas rather than a spin chain, and that several figures show real experimental data.
• Worked examples, history and applications. The publisher describes copious worked examples, historical background to the main discoveries, exercises at the end of every chapter, and applications from stars to climate. The second edition adds osmosis, diffusion problems, Bayes' theorem, radiative transfer, the Ising model and Monte Carlo methods, with new examples and exercises.

Limitations

• Some topics are thin. The review of the first edition found the treatment of magnetic systems and of the freezing-out of molecular degrees of freedom too short, doubted that the information-theory chapter helps readers who do not already know the material, and called the description of heat as "energy in transit" misleading. Whether the second edition changed these passages is not stated by the publisher.
• Phase transitions. The same reviewer called the phase-transition chapter outdated and asked for numerical examples such as the Ising model and Monte Carlo simulation. The second edition adds both topics, but it cannot be confirmed from the contents alone how far they answer that criticism; instructors may still want supplementary material.
• Ideal-gas assumptions in kinetic theory. The reviewer could not find a clear statement of where the ideal-gas approximation enters the early kinetic-theory chapters.
• Problem coverage and length. The reviewer found the problems well chosen but wanted more, especially problems applying the concepts to other disciplines. The special-topics chapters, he expected, would be dropped in a one-term course.

Where It Fits in the Course

Blundell and Blundell is a general undergraduate text for the whole subject, and it is distinctive for the order it takes: probability, kinetic theory and the laws of thermodynamics first, the partition function afterwards. Schroeder's An Introduction to Thermal Physics does the opposite and defines temperature and entropy through the counting of microstates from the start, so the two books suit readers who prefer, respectively, a thermodynamics-first or a statistics-first route. Baierlein's Thermal Physics is described on its page as developing thermodynamics and statistical mechanics together through microscopic states and probability.

For a gentler start, Rex's revision of Finn's Thermal Physics is a concise introduction to classical thermodynamics with statistical mechanics added later, and Lemons's A Student's Guide to Entropy is a short guide to the single concept that links thermodynamics, statistical mechanics and information theory. Pathria and Beale's Statistical Mechanics is the graduate step beyond Blundell's Parts VII–VIII, starting from ensemble theory.

How to Use This Book

The book suits second- or third-year physics students and strong students from chemistry or engineering. First-year calculus with partial derivatives and introductory mechanics are enough; a dedicated probability chapter (Chapter 3) comes before temperature is introduced.

For a one-term course, a workable core is Chapters 1–4, then Chapters 11–14 and 16 for the laws and potentials, then Chapters 19–22 for the partition function, the ideal gas and the chemical potential, and Chapters 29–30 for the quantum distributions. According to the first-edition review, Part II can be postponed or omitted apart from its first two chapters (the Maxwell–Boltzmann distribution and pressure). Chapters 15, 17 and 25–27 and Part IX are natural optional extensions: information theory, magnets and bubbles, relativistic and real gases, and the applications to stars and the atmosphere.

Work the exercises at the end of every chapter as the main way of checking understanding. Readers who find Chapter 28 on phase transitions brief can read it together with a separate treatment of the Ising model; those who want a statistics-first introduction can read Schroeder's opening chapters alongside Chapters 3–4 and 19–20.