1. Unit 1: Reaction Kinetics
Start heating demo at start of class (on medium heat). If it gets too hot, cool it in a cold water bath.
Lesson 6: Activation Energies (Part I)

2. An Energy Barrier
We’ve seen that molecules must possess a minimum amount of energy in order to react.
This energy requirement is a barrier that molecules must overcome in order to react.

3. Demo Time! Observe: What do you see?
Explain: What do you think happened?
*Prep in advance!! Demo 12.I.15 – 10 min

4. Activated Complex
The activated complex is the arrangement of atoms that occurs when reactants are in the process of rearranging to form products. It is extremely unstable and exists for only a short period of time.
Activation energy (Ea) is the minimum potential energy required to change the reactants into the activated complex.

5. Brain Break!
5 min

6. Energy Conversions During Reactions
As molecules approach each other,
electrons repel,
molecules slow down,
KE converts to PE
Once products are formed,
electrons repel,
molecules move away from each other and speed up,
PE converts to KE
Note: the total amount of energy does not change! It just converts between PE and KE.

7. Putting It All Together
(Graph is on page 21 of the textbook.)
Explain graph and how it relates to reaction rate – 5 min

8. Don’t Forget Geometry!
If the reactants are not correctly aligned, the activation energy is greater. The activation energy shown in a PE diagram is a theoretical value that assumes perfect alignment of the reactant molecules.

9. Practice:
Pg. 23 #34-40
10 min