Home Page Overview Site Map Index Appendix Illustration About Contact Update FAQ


Thermodynamics


Contents

Terminology
The Four Laws of Thermodynamics
Entropy
Systems
States
Thermodynamic Process
Work and Engines
Connection to the Microscopic View

Terminology

Thermodynamics is the branch of science that deals with the conversions of various forms of energy and the effect on the state of a system. It was developed in the 19th century, when it was of great practical importance in the era of steam engines. Since the microscopic structure of matter is not known at that time, it can only prescribe a macroscopic view. It remains valid and useful in the 21th century, but now we understand such macroscopic description is just the averaged behaviour of a large collection of microscopic constituents.

Some thermodynamics definitions here such as temperature, pressure, and density are specified under an equilibrium condition. The changes in these variables are idealized with a succession of equilibrium states. Many important biochemical and physical
Thermodynamics Theory processes (such as in microfluid, chemical reactions, molecular folding, cell membranes, and cosmic expansion) operate far from equilibrium, where the standard theory of thermodynamics does not apply. Figure 01a shows the cases for different kinds of thermodynamic theory. Case 1 is for over all equilibrium in the system, which is described by classical thermodynamics. Case 2 has local equilibrium in different regions. A theory of nonequilibrium thermodynamics (using the concept of flow or flux) has been developed for such situation. In case 3 the molecules become a chaotic jumble such that the concept of

Figure 01a Thermodynamics Theory [view large image]

temperature is not applicable anymore. A new theory has been formulated by using a new set of variables within the very short timescale for the transformation. The second law of thermodynamics has been shown to be valid for all these cases.

Go to Next Section
 or to Top of Page to Select
 or to Main Menu

.