2. Elementary phenomena occurring at the interface

The processes taking place at the interface are identified either by building a model of its behavior, or by trying to find the value of certain parameters when the reaction mechanism involved is already known. However, in some practical cases, empirical relationships are sufficient to obtain functional tests.

The study of a physical-chemical phenomenon often leads to the development of a model. What we're looking for is a rational representation, often in the form of differential equations, of a phenomenon that contains only the essential features of the actual situation. Such a model has two aims:

• First, it must take into account all the facts discovered experimentally;

• then it must predict the system's behavior under various conditions.

A model...