A Level Chemistry OCR Practice Exam

What is the minimum energy requirement for particles to initiate a reaction called?

1. Thermal energy

2. Activation energy

3. Kinetic energy

4. Potential energy

The correct answer is: Activation energy

The minimum energy requirement for particles to initiate a reaction is termed activation energy. This energy threshold is crucial because it determines whether the reactants have sufficient energy to overcome the energy barrier associated with the reaction, allowing for the formation of products. Activation energy is a specific concept in chemical kinetics, which explains why some reactions proceed quickly while others do not, even if the reactants are present. For a reaction to occur, particles must collide with enough energy to break bonds, rearrange atoms, and form new bonds, which is why activation energy is essential. While thermal energy relates to the energy available in substances due to temperature, and kinetic energy pertains to the energy possessed by an object due to its motion, neither directly specifies the energy necessary to initiate a chemical change. Potential energy is associated with the position of particles and can influence the overall energy of the system but does not define the energy needed for a reaction to occur. Hence, activation energy is the correct term that encapsulates this specific requirement for chemical reactions.