One of the goals of the study of kinetics is to have a tool for predicting rates of reactions under different conditions. The effects of temperature and concentration on the rate of a reaction can be quantified in an expression known as a rate law. Rate laws have this general form:
rate = k[A]m[B]n[C]p........
where k is the rate constant (the temperature dependent part of the rate law), [A], [B] and [C] are usually reactant concentrations, and the exponents m, n, p, etc. are called the orders of the reaction (which are in some way related to the significant collisions).
The values of k, m, n, p, etc. can only be determined experimentally. There are a few different ways to do this. For example, the concentrations of reactants and products change regularly during a reaction and these changes can generally be described by simple functions.