IB Chemistry syllabus and notes

6.2 - Collision theory

6.2.1 Describe and explain the collision theory. Students should know that not all collisions lead to a reaction.

6.2.2 Define activation energy (Ea) and explain that reactions occur when reacting species have E < Ea.
Molecules must have a minimum energy and appropriate collision geometry in order to react. A simple treatment is all that is required. Cross reference with 5.1.3 and 5.1.4.

6.2.3 Predict and explain, using collision theory, the qualitative effect of particle size, temperature, concentration and catalysts on the rate of a reaction. Increasing the temperature increases the frequency of collisions but, more importantly, the proportion of molecules with E < Ea increases.

6.2.4 Explain that reactions can occur by more than one step and that one step can determine the rate of reaction.

Few reactions involve just one step although one step in the reaction, the rate determining step, determines the reaction rate. Orders of reactions and rate laws are not required.

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