How does increasing the temperature increase the rate of a reaction?

In order for a reaction to take place molecules must collide with enough energy, which is known as the activation energy. Therefore when you heat a reaction mixture the heat energy is converted into the kinetic energy of the molecules. This means the molecules move around faster so there are more frequent collisions, so the rate of the reaction increases. It also means that more molecules have enough energy for the reaction to take place, which is the activation energy, so there are more successful collisions, which increases the rate of the reaction.