How is collision theory linked to rates of reaction?
Collision theory explains how we can increase reaction rates.
Collision theory is closely 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 - hence, 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.
If you increase the concentration of the particles in the solution, or you increase the surface area, now there are more particles to bump into, and the reaction rate goes up.
Adding a catalyst makes the collisions that do occur more effective, by lowering the activation energy needed for the reaction.