Collision Model – Terminology
Effective Collision: a collision between particles that leads to bond breaking and bond forming.
Proper orientation: for a
collision to be effective, the colliding particles must be oriented in
such a manner that the proper parts of the molecules collide.
Sufficient Energy: colliding particles must possess an amount of kinetic energy that surpasses the activation energy for the reaction.
Activated Complex: the short-lived intermediate structure that exists at the maximum energy location along the reaction pathway.
Reaction Mechanism: the collection of steps by which reactants turn to products, forming several intermediate and short-lived species
Rate-Determining Step: the
slowest step of a reaction mechanism. Not all steps of a mechanism
occur at the same rate. The slowest step determines the overall rate of
Important Note: For non-rate-determining steps, the concentration of reactants and products can be related by the equation:
[Reactants] = k • [Products] where k is a proportionality constant
Catalyst: a chemical that
speeds up the rate of a reaction. The catalyst often alters the
mechanism so that the activation energy is lowered.
Role of Temperature: an
increase in temperature increases the rate. At higher temperatures,
there are a greater number of particles with a kinetic energy that
surpasses the activation energy.
Role of Concentration: an
increase in concentration increases the rate because more collisions
can occur in more regions of space where particles are more
Role of Surface Area: an
increase in surface area increases the rate because there are more
particles in the sample that are "freed up" and available for