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How does activation energy affect whether a chemical reaction can occur?

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combustion — chemical reaction Log burning in a fire. Burning wood is an example of a chemical reaction in which wood in the presence of heat and oxygen is transformed into carbon dioxide, water vapor, and ash.

Activation energy is the minimum amount of energy required for atoms or molecules to reach a state where they can undergo a chemical transformation. It acts as an energy barrier that must be overcome for a reaction to occur.12

According to collision theory, a collision between reactant species will only be effective in producing a chemical change if the particles possess internal energy equal to or greater than the activation energy. If the colliding particles have less energy than this threshold, they will simply separate unchanged. Furthermore, the particles must be oriented in a manner favorable to the necessary rearrangement of atoms and electrons.32

Because only a fraction of molecules possess energy exceeding the activation energy at a given temperature, the activation energy directly influences the reaction rate. Catalysts can facilitate reactions by providing an alternative pathway that lowers the required activation energy, thereby increasing the rate at which the reaction proceeds.24