1. Unit 5: Thermochemistry
Reaction Energy Diagrams

2. Thermochemistry
thermochemistry: studies the relationships between chemical reactions and energy changes involving heat

3. Thermochemistry Heat and temperature are NOT the same thing!
Heat: transfer/flow of energy due to a temperature difference (from high to low)
Temperature: a measure of the random motions of molecules (average kinetic energy)

4. Reaction Energy Diagram
Reaction energy diagrams show the energy changes throughout the reaction
Activated complex
(Also called the transition state)
Activation Energy
Products
Energy
Energy change for reaction
Reactants
Reaction proceeds

5. energy EXITS the system
Exothermic Reactions
Exothermic:
energy EXITS the system
E<0 (neg.)
System
Energy
Surroundings

6. Endothermic Reactions
energy ENTERS the system
E>0 (pos.)
System
Energy
Surroundings

7. Catalysts create a lower energy reaction pathway
Activated complex
(Also called the transition state)
Activation Energy
Products
Energy
Energy change for reaction
Reactants
Reaction proceeds