文档介绍：1. Introduction
Motivation
The subject of the book is intermolecular forces. Intermolecular forces are
the forces which cause attraction in the absence of chemical bonding. We are
all aware of this attraction, since these forces appear in our everyday lives:
intermolecular forces are, for example, responsible for the sticking together
of snowballs and the appearance of surface tension. The formation of wa-
ter droplets is a direct consequence of the existence of intermolecular forces
between the water molecules.
These forces, which are about two orders of magnitude weaker than chem-
ical bonds, are responsible for many phenomena in science, including some
of the properties of real gases, as below:
• Van der Waals discovered in 1873 that real gases deviate from the ideal-
gas equation. He concluded that the existence of attractive intermolecular
forces results in a reduction of the measured pressure. This resulted in
the proposal of an equation describing real gases very accurately, which is
known today as the van der Waals equation:
p + a/V 2 (V − b)=NkT ,
with p, V, N, k, and T being the pressure, the volume, the number
of molecules, the Boltzmann constant and the temperature of the gas,
respectively; a and b are parameters which characterize the deviation from
an ideal gas. The constant b has to be introduced since each molecule has
a fin