Grade 12 · Chemistry
Collision theory
Why it matters
Why some collisions cause reactions and others do not.
Advanced20m readingPrerequisite: Factors affecting rates of reaction
What is collision theory?
Short answer
Collision theory explains reaction rates in terms of particle collisions. For a reaction to occur, particles must collide with enough energy (at least the activation energy) and in the correct orientation. Only a fraction of collisions meet both conditions. Anything that increases the frequency or energy of effective collisions — higher concentration, temperature, or a catalyst — speeds up the reaction.
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Frequently asked questions
- What makes a collision effective?
- The particles must collide with at least the activation energy and in the right orientation to rearrange bonds.
- How does temperature affect collisions?
- Higher temperature raises particle speed, so collisions are more frequent and a greater fraction exceed the activation energy.