Collisions need energy
Colliding is not enough on its own. For colliding reactant particles to turn into products, they must carry enough energy.
The reason is plain. The first step is breaking the existing bonds, and breaking a bond takes energy. In a feeble collision the two particles simply bounce apart again, unchanged.
A collision without enough energy
The two particles bounce apart. No bond breaks, and no product is formed.
A collision with enough energy
Bonds break and new bonds are built. A product is formed.
So there are two things we can raise
To increase the rate of reaction we have to increase the number of successful collisions in unit time. There are two ways of doing that:
- Increase the number of collisions
- Increase the energy of the collisions
Each of the four factors on the next page does one or both of these. That is why all four explanations come back to the same single idea.