Collision Theory

Key Questions

• Temperature changes both the frequency and effectiveness of collisions.

Collision theory is related to the kinetic-molecular theory. This explains how all matter is made of particles, and those particles are in constant motion. As they move around, sometimes they collide into one another. If they collide in the right orientation, and with enough energy, the particles rearrange in new combinations - a reaction has occurred.

According to the collision theory, there are two ways to increase reaction rate: increase the frequency of collisions, and increase the fraction of collisions that are effective.

If you speed up the particles by increasing temperature, there is a greater likelihood that they will bump into one another, and the reaction rate goes up. The total energy within the particles is also increased; so when they do collide, they do so with more energy, increasing the fraction of effective collisions.

The video below discusses these ideas using a simulation from PhET

Video from: Noel Pauller