Thermal physics: Second edition by C. B. P. Finn, Chapman and Hall, London-Glasgow-New York-Tokyo-Melbourne-Madras, 1993 physics and its applications series, volume 5, 256 pages price: ß13.95

The chemical potential is a quantity for which students hardly have an intuitive feeling in contrast to other intensive quantities like pressure or temperature. Some students may believe that this is not really an insufficiency because the chemical potential seems to be essentially a quantity for chemists. We will try to show that the chemical potential does not merit its reputation as a difficult to understand quantity. Not only is it easy to grasp, it is a particularly intelligible quantity for which even the layman can develop a feeling. Moreover, this quantity is not only important for chemists. It is just as useful for describing physical phenomena and processes, such as phase transitions, the stratification of gases in a gravitational field and electric currents in semi-conductor junctions and nuclear reactions, to mention just a few.

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Chemical potential—a quantity in search of recognition

The universe seen at different scales

We present a theory for the behavior of a solid undergoing two interdependent processes, a macroscopic or mechanical process due to the deformation of the solid and a microscopic or chemical process due to the migration of a chemical species through the solid. The principle of virtual power is invoked to deduce the basic balances of the theory, namely the mechanical force balance and the transport balance for the chemical species. In combination with thermodynamically consistent constitutive relations, these balances generate the basic equations of the theory. Keeping in mind applications involving the swelling of polymer networks by liquids, a specialization of the theory is presented and applied to study the influences of mechanical and chemical interactions on equilibrium states and diffusive dynamical processes. It is shown that the possibility of a mechanically induced phase transition is governed by two parameters: the Flory interaction parameter and a parameter given by the product between the number of cross-linked units per unit reference volume and the molecular volume of the liquid molecule. As for diffusion, it is shown that the theory is able to describe the pressure-induced diffusion in swollen membranes.

http://www.turbulencia.coppe.ufrj.br/artigos/2010/2010_DUDA_JMPS_v58_p515-529.pdf

A theory for species migration in a finitely strained solid with application to polymer network swelling

Plasmonic gold nanorod instability and reshaping behavior below melting points are important for many future applications but are yet to be fully understood, with existing nanoparticle melting theories unable to explain the observations. Here, we have systematically studied the photothermal reshaping behavior of gold nanorods irradiated with femtosecond laser pulses to report that the instability is driven by curvature-induced surface diffusion rather than a threshold melting process, and that the stability dramatically decreases with increasing aspect ratio. We successfully utilized the surface diffusion model to explain the observations and found that the activation energy for surface diffusion was dependent on the aspect ratio of the rods, from 0.6 eV for aspect ratio of 5 to 1.5 eV for aspect ratio less than 3. This result indicates that the surface atoms are much easier to diffuse around in larger aspect ratio rods than in shorter rods and can induce reshaping at any given temperature. Current plasmo...

https://researchbank.swinburne.edu.au/file/372dda35-0218-4ccb-bf49-707dc6cd7d9c/1/PDF (Accepted manuscript).pdf

Below melting point photothermal reshaping of single gold nanorods driven by surface diffusion

This paper offers some qualitative understanding of the chemical potential, a topic that students invariably find difficult. Three “meanings” for the chemical potential are stated and then supported by analytical development. Two substantial applications—depression of the melting point and batteries—illustrate the chemical potential in action. The origin of the term “chemical potential” has its surprises, and a sketch of the history concludes the paper.

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The elusive chemical potential

Thermodynamics in introductory physics typically begins with the ideas of temperature and heating and with the first law of thermodynamics. Then the more difficult parts come: entropy and the second law of thermodynamics. This second portion of the course can begin with a microscopic conception of entropy and a qualitative idea of how thermal systems evolve. The key concept is the ‘‘multiplicity of a macrostate:’’ the number of microstates associated with a macrostate. Starting from these notions—a point of departure and a concept—this paper develops the second law of thermodynamics, the relationship ΔS≥(energy input by heating)/T, and the Carnot efficiency. Offer the entire development both as a specific alternative to what appears in typical introductory texts and as a contribution to a continuing discussion of how to teach thermodynamics to various college audiences.

Entropy and the second law: A pedagogical alternative

First I provide some history of how the equation E=mc2 arose, establish what “mass” means in the context of this relation, and present some aspects of how the relation can be understood. Then I address the question, Does E=mc2 mean that one can “convert mass into energy” and vice versa?

Does nature convert mass into energy

Misconceptions about special relativity theory are common and pernicious. I address two such misconceptions: the low-speed behavior of the Lorentz transformation and the meaning of the phrase, “the constancy of the speed of light,” as Einstein used it in 1905.

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Ralph Baierlein

Papers

The elusive chemical potential

Entropy and the second law: A pedagogical alternative

Does nature convert mass into energy

Two myths about special relativity

Representing a vector field: Helmholtz’s theorem derived from a Fourier identity