Thermodynamics and Kinetic Theory

Thermodynamics is the study of the macroscopic physical properties of a large collection of particles. That is, instead of attempting to describe the individual motion of the microscopic particles, one tries to make statements about the properties of the system as a whole. One says that a system has reached thermodynamic equilibrium when the macroscopic properties do not change with time. The word system used here refers to the part of the world that one is interested in studying. Hence the world is conveniently divided into the system, and an exterior or environment. Note: Historically, the fields of kinetic theory and statistical mechanics were developed even before there was direct proof about the reality of atoms. Some indirect evidence that fluids consist of fast moving molecules was provided by observations in 1827 by the botanist Robert Brown who noticed the jiggling motion of pollen grains suspended in water. After many careful experiments he came to conclude that the motion was real and existent even for inorganic suspensions. It came to accepted by scientists that this motion of the suspended particle was due to the constant and random bombardment it suffered from all sides by molecules of the liquid. A quantitative explanation of the motion was later provided by Einstein.