Final answer:
The minimum energy required to start a chemical reaction is called activation energy (E₂) and is necessary for reactant molecules to collide and form product molecules. The activation energy affects the rate of the reaction.
Step-by-step explanation:
The minimum energy required to start a chemical reaction is called the activation energy (E₂). This energy is necessary for reactants to collide and form the activated complex, from which product molecules are formed. The activation energy determines the rate of a chemical reaction, with a higher activation energy leading to slower reactions.
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