The activation energy which changes with temperature
The arrhenius constant which depends on the temperature
Explanation:
There are deviations from the Arrhenius law during the glass transition in all classes of glass-forming matter.
The Arrhenius law predicts that the motion of the structural units (atoms, molecules, ions, etc.) should slow down at a slower rate through the glass transition than is experimentally observed.
In other words, the structural units slow down at a faster rate than is predicted by the Arrhenius law.
This observation is made reasonable assuming that the units must overcome an energy barrier by means of a thermal activation energy.
The thermal energy must be high enough to allow for translational motion of the units which leads to viscous flow of the material.
Both the Arrhenius activation energy and the rate constant k are experimentally determined, and represent macroscopic reaction-specific parameters that are not simply related to threshold energies and the success of individual collisions at the molecular level.
Consider a particular collision (an elementary reaction) between molecules A and B. The collision angle, the relative translational energy, the internal (particularly vibrational) energy will all determine the chance that the collision will produce a product molecule AB.
Macroscopic measurements of E(activation energy) and k(rate constant ) are the result of many individual collisions with differing collision parameters. They are averaged out to a macroscopic quantity.
