Collide with enough energy to react
Collide in the right orientation to react (the more frequent the collisions, the more likely this is)
- Particles collide more frequently if there is more surface area, as there is more contact between the reactants. Faster rate of reaction.
- There is more chance of particles colliding at a higher concentration/pressure, so they react more often. Faster rate of reaction.
- Particles move about more and will collide more frequently the higher the temperature; react more often. Increases the rate of reaction.
- Provides an alternative pathway for the reaction to start which requires a lower activation energy.