Activation Energy

Contents

Key Stage 4

Meaning

Activation energy is the amount of energy needed to begin a chemical reaction.

About Activation Energy

Foundation

Chemical reactions can't take place unless there is enough energy to cause the reactant molecules to collide and react.

Different reactions need different amount of activation energy to start.

The activation energy can be reached by heating the mixture of reactants until they have enough energy to react.

Sometimes reactants at room temperature have enough energy to react. If the mixture of reactants was lower than room temperature they might not have enough energy to begin reacting.

Once the activation energy is reached the reaction will continue as energy is released when chemical bonds form to make the products.

Higher

Activation energy is needed to allow the reactant molecules to collide with one another hard enough to break the bonds holding them together. This allows new bonds to form making the product.

Examples

The activation energy is shown in this reaction profile for an exothermic reaction.	The activation energy is shown in this reaction profile for an endothermic reaction.