1. Thermodynamics

2. Energy and Chemical Reactions
During a chemical reaction heat can be either absorbed or released.
As the reactants become the products energy can be released  exothermic
As the reactants become the products energy can be absorbed  endothermic

3. Energy
The energy levels of the reactants and the products will be different.
ΔH = Enthaply  The difference in the energy levels of a reaction.
ΔHreaction = ΔHproducts – ΔHreactants
ΔH is negative for exothermic reactions
ΔH is positive for endothermic reactions

4. Activation Energy
Many reactions require an input of energy for them to start, this is known as Activation Energy.
The ΔH of the reactants, products and activation energy can be graphed.

5. Energy Change Graphs
The variables of energy and reaction path/progress are graphed.
The amount of energy required to push the reactants over the edge, to start the reaction, is the activation energy.
Once at this point the reaction takes place and products are formed.
The difference in the energy of the reactants and products is the ΔH

6. Exothermic Reaction Plots
In exothermic reactions energy of the products is less than the reactants.
Energy is released (heat is given off).
ΔH is negative.

7. Endothermic Reactions
Endothermic reactions usually have a steep activation energy, because the energy of the products is MUCH higher than the reactants (LOTS of energy input).
ΔH is positive (energy absorbed).

8. Entropy Another factor influencing reactions is known as Entropy (ΔS).
Entropy is a measure of the random disorder in a reaction.
With respect to molecules in phases:
Phase
Amount of Entropy
Solid
Low
Liquid
Medium
Gas
High

9. Gibbs Free Energy Enthalpy and Entropy both influence reaction rate.
Free energy is a measure of the available energy to do work.
ΔG = ΔH - T ΔS
ΔG = Free energy
ΔH = Enthalpy
ΔS = Entropy
T = Temperature

10. Will not proceed on its own
Gibbs Free Energy
Spontaneous reactions occur on their own, without any outside energy input.
This depends upon ΔS, ΔH and ΔG ΔG
Reaction Behavior
Negative
Spontaneous
Zero
Equilibrium
Positive
Will not proceed on its own