What factors affect the rate of a chemical reaction?
Short answer
The rate of reaction increases with higher temperature, higher concentration (or pressure for gases), larger surface area and the presence of a catalyst. Collision theory explains why: particles react only when they collide with enough energy (the activation energy), and each factor increases the frequency or energy of collisions.
Step by step
- Temperature: particles move faster, collide more often and more collisions have enough energy.
- Concentration or pressure: more particles in the same space, so more frequent collisions.
- Surface area: smaller pieces or powder expose more particles to collisions.
- Catalyst: provides a different pathway with a lower activation energy and is not used up.
Worked example
Marble chips and hydrochloric acid
- Powdered marble reacts faster than large chips
- Warmer acid reacts faster than cold acid
- Measure the rate by recording the volume of CO₂ given off each minute
Common mistakes
- Saying particles collide harder at higher concentration. They collide more often, not harder.
- Saying a catalyst gives particles more energy. It lowers the activation energy instead.
- Leaving out the word frequency when explaining collision theory.
Useful for:GCSEIGCSEWAECMatric
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