As you increase the temperature of the reaction, the particles gain kinetic energy. This causes them to move faster and as a result, the frequency of collisions increases. This means there is an increased proportion of collisions with energy greater than or equal to the activation energy, so it is easier for the reaction to occur, which increases the rate. The activation energy is the minimum energy required by the collision between two particles for them to react. An opposite effect is seen with lowering the temperature, which lowers the rate of reaction.