What is the minimum energy that colliding particles must possess to start a reaction?

• A. Activation energy
• B. Kinetic energy
• C. Potential energy
• D. Heat of reaction

Answer: (A)

Activation energy is the energy barrier that must be overcome for a reaction to proceed when two particles collide. In collision theory, only collisions with enough energy to reach the transition state can form products; those with less energy simply bounce apart. This threshold explains why reactions speed up with temperature—more molecules have energy above the barrier, so more successful collisions occur. The other ideas don’t set this specific starting point: kinetic energy is the general energy of motion, not the required barrier; potential energy is energy due to position, not the energy needed to start bond-making or breaking; and heat of reaction is the overall energy change, not the energy needed to initiate the process.