Question

which is the best definition of activation energy?
○ the energy required to end a chemical reaction
○ the energy required to bind a substrate to an active site
○ the energy required to form or break the bonds of reactant molecules
○ the energy required to re-form bonds in product molecules

Explanation:

1. Analyze the first option: Activation energy is not for ending a reaction, so this is incorrect.
2. Analyze the second option: Binding a substrate to an active site is related to enzymes but not the definition of activation energy, so this is incorrect.
3. Analyze the third option: Activation energy is the minimum energy needed to start a reaction, which involves forming or breaking bonds of reactant molecules to initiate the reaction, so this is correct.
4. Analyze the fourth option: Re - forming bonds in product molecules is part of the reaction process after the activation energy has been overcome, not the definition of activation energy, so this is incorrect.

Answer:

the energy required to form or break the bonds of reactant molecules