Collision Frequency
The number of collisions occurring per unit volume per unit time in a reacting mixture.
Formula / equation
Z ∝ n²σ√T
Unit
s⁻¹
In depth
Collision frequency rises with concentration, with molecular size and with the square root of absolute temperature. Because it depends on temperature only through a square root, it cannot by itself explain the dramatic acceleration of reactions on heating — the exponential energy term does that.
Examples in the real world
A gas at room temperature and pressure experiences around 10³⁴ collisions per cubic metre per second.