Collision Theory and Factors Affecting Rate

Collision theory is the model used to explain why different factors change the rate of a chemical reaction. This lesson covers the core ideas of collision theory, activation energy, and the five main factors that affect rate. Understanding these concepts is essential for the AQA GCSE Combined Science Trilogy specification (8464).

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Collision Theory

For a chemical reaction to occur, two conditions must be met:

1. Reactant particles must collide with each other.
2. The collision must have sufficient energy (equal to or greater than the activation energy) and the particles must collide with the correct orientation.

A collision that meets both conditions is called a successful collision. Collisions that do not meet both conditions are unsuccessful — the particles simply bounce apart.

Key Definition: The activation energy is the minimum amount of energy that colliding particles need for a reaction to take place.

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Factors That Affect the Rate of Reaction

There are five main factors that affect rate. Each can be explained using collision theory.