1. Collision Frequency: This refers to the number of collisions that occur between reactant molecules per unit time. For a reaction to occur, molecules must collide, but not all collisions lead to reactions. Factors like concentration, temperature, and surface area affect collision frequency.

2. Activation Energy: This is the minimum amount of energy that colliding molecules must possess in order to break existing bonds and form new ones, leading to a successful reaction. Only collisions with energy equal to or greater than the activation energy will result in a reaction.

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