Activation energy is the minimum energy that colliding particles must have for a collision to be effective and a reaction to occur.
Activation energy is the minimum energy that colliding particles must have for a collision to be effective and a reaction to take place. Malay: tenaga pengaktifan · Chinese: 活化能.
Before reactant bonds can break so that new ones form, the particles need a certain minimum amount of energy at the moment they collide. This energy barrier is the activation energy, usually given the symbol Ea. A collision with less than this energy simply bounces apart; only a collision with at least this much energy can be effective. A reaction with a low activation energy goes readily, while one with a high activation energy needs more energetic collisions and is often slower at room temperature.
Example. On an energy profile diagram, the reactants sit at one level and the products at another, but between them the curve rises to a peak. The height of that peak above the reactants is the activation energy: it is the hill the particles must climb before they can roll down to become products. Heating the mixture gives more particles enough energy to get over this hill, so more collisions are effective and the rate rises.
Confusion to avoid. Do not confuse activation energy with the overall energy change of the reaction. The activation energy is the barrier that must be overcome to start the reaction; the energy change is the difference in level between reactants and products. A reaction can be exothermic overall yet still have a real activation energy that must be supplied first.
Activation energy is the barrier that a positive catalyst lowers by offering an alternative path, and it is central to how temperature affects rate, so SPM Chemistry expects the exact word minimum in the definition.
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