Revise: Controlling the rate Activation energy

Temperature is a measure of the average kinetic energy of the particles in a substance. The activation energy is the minimum energy required for a reaction to occur. This means that the reactant molecules have enough kinetic energy to collide successfully and overcome the repulsion caused by outer electrons.

If the activation energy is high for a reaction, then only a few particles will have enough energy to collide so the reaction will be slow.

If a reaction has a low activation energy then the reaction will be fast as a lot of particles will have the required energy.

By showing the activation energy on a graph, we can see how many molecules have enough energy to react.

The effect of temperature, on a reaction, can be shown using these graphs.

Line T₂ shows a slight increase of temperature so causes a large increase in the number of molecules with kinetic energy (E_K) greater than the activation energy (E_K > E_A)

There is a significant increase in the rate of reaction. In fact, a 10˚C rise in temperature results in the rate of reaction doubling.