Science · Solutions & reactions
Reaction Rates, Equilibrium, and Catalysts
Estimated time includes reading and one quiz. Take the time you need.
Start here: key ideas
- Reactions occur when particles collide effectively.
- Higher temperature usually increases reaction rate.
- Higher concentration and greater surface area can increase rate.
- Catalysts lower activation energy and are not used up.
- At equilibrium, forward and reverse rates are equal.
What you’ll be able to do
- Use collision ideas to predict rate changes.
- Explain how catalysts work.
- Tell reaction rate from equilibrium.
Predict what changes reaction speed and understand catalysts and dynamic equilibrium.
Optional review
If you’d like to review the basics, visit Chemical Reactions and Equations. You can start this lesson without completing those first.
Why reaction rates change
Particles must collide with enough energy and the right orientation to react. More effective collisions per second mean a faster reaction rate.
Higher temperature makes particles move faster. Higher concentration puts more particles in a space. Greater surface area exposes more particles. Each change can increase collision frequency and rate.
Worked example. A whole tablet reacts more slowly than a crushed tablet in the same liquid. Crushing exposes more surface particles, so collisions happen more often. The chemical identity and final amount possible do not change.
Average rate compares change with time: rate = amount changed ÷ time. If 48 mL of gas forms in 4 minutes, the average rate is 12 mL per minute.
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