9.2 IMPORTANCE OF SCALE
For homogeneous systems, knowledge of properties and phenomena on a
molecular ormicroscopicscale often suffices to understand, or even predict,
what happens on amacroscopicscale. For dispersed systems, it is generally
necessary, or at least useful, to invoke structural elements on an
intermediate ormesoscopicscale. A glance at Figure 9.5 shows, however,
that the linear mesoscopic scale may span a wide range, say, by four orders
of magnitude, and the volume of a cell may be large enough to contain 10^15
(small) molecules.
The size of the structural elements often determines or greatly affects
several properties of a dispersed system. This concerns changes during
processing and storage as well as static properties of the finished product.
Below, some examples of dependencies on scale will be given, for the most
part illustrated for simple dispersions.FIGURE9.5 Length scales. Approximate values.