ABproductsMolecules react only when they collide, and only when the collision is hard enough to get over the energy barrier. Most collisions just bounce. Raise the temperature and every molecule moves faster, but the number moving fast enough to react grows much more steeply, because only the fast tail of the speed distribution clears the barrier. A small rise in temperature therefore speeds a reaction up a lot: as a rule of thumb, 10 °C roughly doubles the rate.