Why does a reaction speed up at higher temperature

In Chapters 1 and 2, we met the idea that the simplest way to increase the energy of a chemical, material or body is to raise its temperature. So heating a reaction mixture gives more energy to its molecules. Although only a tiny proportion of these molecules will ever have sufficient energy to collide successfully and form an activated complex TS, even a small increase in the amounts of energy possessed by a molecule will increase the proportion that 

The simplest way to increase the energy of a chemical, material or body is to raise its temperature - see p. 34. 

By increasing the temperature T, we have not changed the magnitude of the activation energy, nor have we changed the value of AH of reaction. The increased rate is a kinetic result we have enhanced the number of successful reaction collisions per unit time. 

The simplest relationship between temperature T and rate constant k is given by the Arrhenius equation (Equation (8.54)), which relates the rate constant of reaction k with the thermodynamic temperature T at which the reaction is performed  

Heating a reaction mixture increases the number of successful collisions between the reactant species, increasing the amount of product formed per unit time. 

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