# Rate of reaction

How fast a reaction happens. It goes up with higher temperature, higher concentration, larger surface area or a catalyst.

Chemistry (school) · Part 04: Chemical reactions · Card 7 of 9 · Last updated 2026-10-19

## Analogy

More people in a smaller room means more bumps. Reactions need particles to collide.

## Example

**Measuring rate**

Mean rate = amount made / time
60 cm3 of gas in 30 s
Rate = 60 / 30 = 2 cm3/s

## In practice

Powdered chalk reacts with acid faster than a lump because more surface is exposed.

## Practice

### Flashcards

- **Give two ways to increase the rate of a reaction.** Raise the temperature or increase the concentration. A larger surface area or a catalyst also works.

### Interview questions

**Explain, using particles, why increasing the temperature increases the rate of a reaction.**

- Particles move faster
- More frequent collisions
- A larger proportion of collisions have enough energy
- So more successful collisions each second

## Questions people ask

### What is collision theory?

For a reaction to happen, particles must collide with enough energy. The minimum energy needed is the activation energy. Anything that makes collisions more frequent or more energetic, such as a higher temperature or concentration, speeds up the reaction. Particles that collide without enough energy simply bounce apart.

### How do you measure the rate of a reaction that makes a gas?

Collect the gas in a gas syringe and record the volume at regular times. Or put the flask on a balance and record the mass lost as the gas escapes. Plot a graph. A steeper line shows a faster rate, and the line flattens when the reaction stops.

## Related concepts

- [Catalyst](https://studyvisually.com/learn/science/chemistry-school/chemistry-school-part-4/chemistry-school-part-4-concept-8)

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