Activation Energy
The minimum energy that colliding particles must possess for a reaction to occur.
Formula / equation
Ea = E(transition state) − E(reactants)
Unit
kJ/mol
In depth
Activation energy is the barrier that keeps thermodynamically unstable substances from reacting instantly. Because only the high-energy tail of the Maxwell–Boltzmann distribution exceeds it, a small temperature rise produces a large rate increase. Catalysts work by providing a lower-barrier route.
Examples in the real world
Petrol and air need a spark to supply the activation energy; a catalytic converter lowers Ea for CO oxidation.