Besides heating, what other change to a system makes chemical reactants react more frequently?

1. Heating a system causes chemical reactants within it to react more frequently, because molecules collide more often and harder. 2. Increasing the pressure on a system has the same effect. 3. Lowering the pressure would space the molecules out and reduce collisions, so it acts the opposite way. 4. Neither dilution nor reduced surface area is offered as a way of raising reaction frequency here. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 6 "Metabolism", section 6.2 Potential, Kinetic, Free, and Activation Energy_