Collision theory — Science definition
The model that reactions happen only when particles collide with enough energy and the correct orientation.
Where it is taught
- Reaction Rates & Kinetics — Rates & Equilibrium, Physical Science: Chemistry, Grade 11
In use
To understand what sets that speed, chemists use collision theory.
Reaction Rates & Kinetics
Questions using collision theory
Problem 1
- enough energy and the correct orientation
- that a catalyst be present
- that the reaction be exothermic
- only that the particles touch
Answer and explanation
enough energy and the correct orientation
A collision only produces a reaction if the particles collide with at least the activation energy and are properly oriented.
Problem 2
Answer and explanation
Powder has far more exposed surface area than a single lump, so many more zinc atoms are in contact with the acid at once. That allows far more effective collisions per second between zinc and acid particles, which speeds up the reaction.
Problem 3
Answer and explanation
Higher concentration packs more reactant particles into the same volume, so collisions between particles happen more often. More collisions per second means more effective collisions per second, which speeds up the reaction.