Particles need to have a certain minimum energy in order to cause successful collisions. The temperature of a reaction mixture gives a measure of the amount of energy available to the particles. At a higher temperature the particles on average have higher energy. This translates into particles moving faster and more energetically. Consequently, collisions are more frequent and occur with greater energy and more successful.
Understandings Essential idea: The activation energy of a reaction can be determined from the effect of temperature on reaction rate. The Arrhenius equation uses the temperature dependence of the rate constant to determine the activation energy. A graph of 1/T against ln k is a linear plot with gradient - Ea/R and intercept, lnA. The frequency factor (or pre-exponential factor) (A) takes into account the frequency of collisions with proper orientations. Applications and skills Analysing graphical representation of the Arrhenius equation in its linear form. Describing the relationships between temperature and rate constant; frequency factor and complexity of molecules colliding. Determining and evaluating values of activation energy and frequency factors from data. |

In Chapter 6.4