1.1 Thermodynamics and its method
Thermodynamics is the science of the regularities
governing processes of energy conversion.
The fundamentals of thermodynamics were laid in the
nineteenth century when the development of heat engines necessitated the study
of the regularities governing the conversion of heat into work. But later on
the method of thermodynamics stepped over the limits of heat engineering and
found wide application in many branches of physics, chemistry and of other
sciences.
Thermodynamics makes it possible to determine the
direction in which various physical and chemical processes may proceed in
different systems. As it will be seen, thermodynamics reveals the profound
relations between different properties of substance. In principle, this
permits, with the data on the heat capacities of a substance available, to use
thermodynamic methods in calculating, for instance, the density of this
substance, and vice versa.
As distinguished from other branches of physics and
chemistry, thermodynamics does not operate with any models of the structure of
substance, and is in general not related directly to the notions of the
microstructure of substance, which is the strength but also the weakness of
thermodynamics.
Thermodynamics itself is incapable of giving any
data on the properties of substance. But if some of the data are known,
thermodynamic methods permit very interesting and important conclusions to be
drawn.
The construction principle of thermodynamics is simple. Thermodynamics
is based on two main laws, established by experiment. The first law of
thermodynamics characterizes the quantitative side of energy conversion
processes, and the second law sets up the qualitative side (direction) of processes
in physical systems[1]. Making use of these two fundamental laws and applying the method of
strict deduction we can obtain all main conclusions of thermodynamics.
Thermodynamics is applicable to all systems for
which its fundamental laws are true. The first law of thermodynamics, as it
will be seen, is the quantitative expression of the law of conservation and
conversion of energy, and it is of a general nature. As to the second law, it
is based on the experience accumulated in observing and studying macro systems
within the scope accessible to direct observation.
Given in this chapter below are the necessary
primary data, concepts and definitions preceding the treatment of
thermodynamics proper.
[1] Neither the first nor the second law of
thermodynamics rests upon any assumptions on the structure of substance, and it
is precisely this fact that ensures, as it was already mentioned above, the
great generality of the methods of thermodynamics.