Rates of Reaction: Collision Theory

Collision Theory is the fundamental principle used to explain how chemical reactions occur and why reaction rates differ.
It states that for a chemical reaction to take place, the reactant particles must collide with each other. Not all collisions, however, cause reaction; only those with sufficient energy to overcome the activation energy barrier.
Activation energy is the minimum amount of energy required for a chemical reaction to occur. It’s the energy needed to break the bonds in reactant molecules so that new ones can form in the product molecules.
The rate at which a chemical reaction proceeds is directly proportional to the frequency of effective collisions. An effective collision is one where particles collide with sufficient energy and an appropriate orientation, leading to a successful reaction.
Factors such as concentration, surface area, temperature and presence of a catalyst affect the rate of a reaction. These all influence either the energy of the reactant particles or the frequency of their collisions.
When the concentration of the reactants is higher, or the surface area of solid reactants is increased, the frequency of collisions is increased, hence the reaction rate increases as well.
Temperature influences both the energy of particles and the frequency of collisions. When temperature increases, particles move faster and collide more often and with more energy, thus increasing the reaction rate.
A catalyst speeds up a reaction by providing an alternative reaction pathway with a lower activation energy, increasing the number of effective collisions.
Remember, it’s the effective collisions (those with both the right orientation and enough energy) that matter in reaction rates, not just the overall number of collisions.
Practice interpreting reaction rate graphs and understand how changing conditions such as temperature, concentration, surface area and use of catalysts impact the speed of reactions.

Refer to the equations and reactions provided in your course materials and try to identify and understand how each aspect of the Collision Theory applies. This will provide a solid foundation for mastering the topic and performing well in any future assessments.