Rate of reaction and collision theory
Rate of reaction
- The rate of reaction is how fast reactants change into products.
- Collision theory: particles must collide, and with enough energy (the activation energy), to react.
- A faster rate = more successful collisions per second.
Practice
According to collision theory, a reaction happens when particles:
Particles must collide AND have at least the activation energy for a successful reaction.
What speeds it up
| Change | Why faster (collision theory) |
|---|---|
| higher concentration | more particles in the same volume → more collisions |
| higher pressure (gases) | particles pushed closer → more collisions |
| larger surface area (powder) | more particles exposed → more collisions |
| higher temperature | particles move faster → more frequent + more energetic collisions |
| a catalyst | lowers the activation energy → more collisions succeed |
Practice
Breaking a solid into a powder speeds up a reaction because it:
More surface area means more particles are exposed, so collisions happen more often.
Practice
Which increase the rate of reaction? (Choose all that apply.)
Higher concentration, temperature and a catalyst all speed reactions up; cooling slows them down.
You've got it
Key idea
- rate = how fast reactants → products; reactions need collisions with enough energy
- faster with higher concentration / pressure / surface area / temperature, or a catalyst
- it's all about more successful collisions per second