Collision theory states that for a chemical reaction to occur, reactant particles must collide with sufficient energy. Reactions proceed faster when collisions are more frequent, either because particles are closer together due to higher concentration or pressure, or because particles have higher energy when they collide at higher temperatures. The speed of a reaction also increases with factors that increase the frequency or effectiveness of collisions between reactants.

1. Summary

2. Collision Theory
• Reaction takes place when
particles collide.
Effective Collision
• Particles must collide with
sufficient energy for reactions
to occur

3. Collision Theory
• More frequent collisions => Faster
reaction
• Particles have higher energy => Faster
reaction

4. Factors Affecting Speed
of Reaction
1) Concentration
High concentration
• Particles are closer together
• Hence, they collide more
frequently
• Faster reaction

5. Factors Affecting Speed
of Reaction
2) Pressure
Pressure is increased
• Particles are squeezed closer
together
• Hence, they collide more
frequently
• Faster Reaction

6. Factors Affecting Speed
of Reaction
3) Temperature
Temperature is increased
• Particles have higher energy when
they collide
• Move faster and hence collide
more frequently
• Faster Reaction

7. Next Lesson
• How particle size affect speed
of reaction?
• Measuring speed of reaction