文档介绍：I. Thermodynamics
Fundamental definitions
• Thermodynamics is a phenomenological description of equilibrium properties of macro•
scopic systems.
⋆ As a phenomenological description, it is based on a number of empirical observations
which are summarized by the laws of thermodynamics. A coherent logical and mathe•
matical structure is then constructed on the basis of these observations, which leads to
a variety of useful concepts, and to testable relationships among various quantities. The
laws of thermodynamics can only be justified by a more fundamental (microscopic) theory
of nature. For example, statistical mechanics attempts to obtain these laws starting from
classical or quantum mechanical equations for the evolution of collections of particles.
⋆ A system under study is said to be in equilibrium when its properties do not change
appreciably with time over the intervals of interest (observation times). The dependence
on the observation time makes the concept of equilibrium subjective. For example, window
glass is in equilibrium as a solid over many decades, but flows like a fluid over time scales
of millennia. At the other extreme, it is perfectly legitimate to consider the equilibrium
between matter and radiation in the early universe during the first minutes of the big bang.
⋆ The macroscopic system in equilibrium is characterized by a number of thermodynamic
coordinates or state functions. mon examples of such coordinates are pressure
and volume (for a fluid), surface tension and area (for a film), tension and length (for
a wire), electric field and polarization (for a dielectric), · · ·. A closed system is an ide•
alization similar to a point particle in mechanics in that it is assumed to pletely
isolated by adiabatic walls that don’t allow any exchange of heat with the surroundings.
By contrast, diathermic walls allow heat exchange for an open system. In addition to the
above mechanical coordinates, the laws of therm