Thermodynamics is the characterization of the states of matter, namely gases,
liquids, and solids, in terms of energetic quantities. The states that will be
considered primarily in these chapters are all macroscopic, although the
same ideas apply at a microscopic level, as will be discussed in Part III. In
thermodynamics, there is a set of rules that objects must obey. The beauty
of these rules is that they are very general and apply to all types of objects,
ranging from gas molecules to cell membranes to the world. It does not
matter how complex the system is, as once the properties are established,
then the rules can be applied. As an example, consider how these ideas
would apply to you. It would be theoretically possible to analyze every
biochemical process in your body and establish the net energy change.
However, at best, this would be a very difficult task and is different for
every person, with athletes such as Lance Armstrong using energy differ-
ently than the average person. Thermodynamics requires that energy is
not lost and so the energy taken into your body must be all converted
into biological processes (provided there is no weight change). Thus, the
complex problem of analyzing all processes can be simplified by looking
at the overall difference, by considering how much energy is available
when you metabolize the food that you eat.
There are three basic thermodynamic ideas that are now identified as laws,
as they have been found to always be applicable. The “zeroth” law pro-
vides a definition of the key energetic parameter of an object: temperature.
The first law defines the conservation of energy that we have just used. The
second law defines how another key parameter, entropy, which defines the
order of an object, can be used to understand how energy can be generated
by allowing systems to become more disordered. The next few chapters
discuss in detail how these rules can be used using certain mathematical
relationships.

1

Basic thermodynamic and

biochemical concepts