The particles in a reacting system  will  have a range of kinetic energies.  As we heat a reactant mixture we will  increase the temperature as the reactant species gain kinetic energy.

The level of energy required to successfully react is know as the activation energy E_A. This energy threshold is very important.

Changing the temperature changes the mean energy of the particles and also distribution of energy in the system

[INS Coll_EU_04_IMA ] 

Now many more reactant species have energy equivalent to or higher than E_A.

Not only is the frequency of collisions increased as the particles move faster but now the number of successful collisions is  increased and thus the rate increases.

The reaction of sodium thiosulfate and acid allows students to investigate the effect of temperature.