*Olivier Darrigol*

- Published in print:
- 2018
- Published Online:
- March 2018
- ISBN:
- 9780198816171
- eISBN:
- 9780191853661
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198816171.003.0005
- Subject:
- Physics, Atomic, Laser, and Optical Physics, History of Physics

This chapter deals with writings in which Boltzmann expressed the statistical nature of the entropy law and temporarily made the relation between entropy and combinatorial probability a basic ...
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This chapter deals with writings in which Boltzmann expressed the statistical nature of the entropy law and temporarily made the relation between entropy and combinatorial probability a basic constructive tool of his theory. In 1881, he discovered that this relation derived from what we now call the microcanonical distribution, and he approved Maxwell’s recent foundation of the equilibrium problem on the microcanonical ensemble. Boltzmann also kept working on problems he had tackled in earlier years. He proposed a new solution to the problem of specific heats, and he performed enormous calculations for the viscosity and diffusion coefficients in the hard-ball model. In a lighter genre, he conceived a new way of determining molecular sizes, and he speculated on a gas model in which the molecular forces would be entirely attractive.Less

This chapter deals with writings in which Boltzmann expressed the statistical nature of the entropy law and temporarily made the relation between entropy and combinatorial probability a basic constructive tool of his theory. In 1881, he discovered that this relation derived from what we now call the microcanonical distribution, and he approved Maxwell’s recent foundation of the equilibrium problem on the microcanonical ensemble. Boltzmann also kept working on problems he had tackled in earlier years. He proposed a new solution to the problem of specific heats, and he performed enormous calculations for the viscosity and diffusion coefficients in the hard-ball model. In a lighter genre, he conceived a new way of determining molecular sizes, and he speculated on a gas model in which the molecular forces would be entirely attractive.

*Dennis Sherwood and Paul Dalby*

- Published in print:
- 2018
- Published Online:
- August 2018
- ISBN:
- 9780198782957
- eISBN:
- 9780191826177
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198782957.003.0006
- Subject:
- Physics, Theoretical, Computational, and Statistical Physics

Definition and mathematics of enthalpy. Definition of heat capacity at constant pressure as CP = (∂H/∂T)V. Endothermic and exothermic reactions. Role of the change in enthalpy as regards the ...
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Definition and mathematics of enthalpy. Definition of heat capacity at constant pressure as CP = (∂H/∂T)V. Endothermic and exothermic reactions. Role of the change in enthalpy as regards the direction and spontaneity of a change in state. Enthalpy changes and phase changes. Measuring enthalpy changes by calorimetry. Hess’s law of constant heat formation. Chemical standards and standard states. Standard enthalpies of formation, ionic enthalpies and bond energies. How the change in enthalpy varies with temperature. Kirchhoff’s equations. Applications of thermochemistry to a variety of worked examples, including flames and explosions.Less

Definition and mathematics of enthalpy. Definition of heat capacity at constant pressure as *C*_{P} = (∂*H*/∂*T*)_{V}. Endothermic and exothermic reactions. Role of the change in enthalpy as regards the direction and spontaneity of a change in state. Enthalpy changes and phase changes. Measuring enthalpy changes by calorimetry. Hess’s law of constant heat formation. Chemical standards and standard states. Standard enthalpies of formation, ionic enthalpies and bond energies. How the change in enthalpy varies with temperature. Kirchhoff’s equations. Applications of thermochemistry to a variety of worked examples, including flames and explosions.