ilya_prigogine_isabelle_stengers_alvin_tofflerbookfi-org

ORDER OUT OF CHAOS 132
processes provide us with the key to the difference between
the behavior of a cry stal and that of a cell?
We will have to consider chemical reactions from a dual
point of view, both kinetic and thermodynamic.
From the kinetic point of view, the fundamental quantity is the
reaction rate. The classical theory of chemical kinetics is
based on the assumption that the rate of a chemical reaction is
proportional to the concentrations of the products taking part
in it. Indeed, it is through collisions between molecules that a
reaction takes place, and it is quite natural to assume that the
number of collisions is proportional to the product of the concentrations
of the reacting molecules.
For the sake of example, let us take a simple reaction such
as A + X B + Y. This "reaction equation" means that whenever
a molecule of component A encounters a molecule of X,
there is a certain probability that a reaction will take place and
a molecule of B and a molecule of Y will be produced. A collision
producing such a change in the molecules involved is a
"reactive collision." Only a usually very small fraction (for
example, 111 (6) of all collisions are of this kind. In most cases,
the molecules retain their original nature and merely exchange
energy.
Chemical kinetics deals with changes in the concentration
of the different products involved.in a reaction. This kinetics is
described by differential equations, just as motion is described
by the Newtonian equations. However, in this case, we are not
calculating acceleration but the rates of change of concentration,
and these rates are expressed as a function of the
concentrations of the reactants. The rate of change of concentration
of X, dXldt, is thus proportional to the product of
the concentrations of A and X in the solution-that is,
dXldt= -kA'X, where k is a proportionality factor that is
linked to quantities such as temperature and pressure and that
provides a measure for the fraction of reactive collisions taking
place and leading to the reaction A + X Y + B. Since, in
the example taken, whenever a molecule of X disappears, a
molecule of A disappears too, and a molecule of Yand one of
B are formed, the rates of change of concentration are related:
dXldt=dAldt= -dYldt= -dBldt.
But if the collision between a molecule of X and a molecule