1. Aim: How do entropy and enthalpy affect reactions?
Do Now:
Take out a calculator and reference tables.
Consider the following reaction:
2SO2(g) + O2(g) 2SO3(g) + heat
Describe what can be done to shift the equilibrium to the right.
What could be done to shift the equilibrium to the left?

2. 2SO2(g) + O2(g) 2SO3(g) + heat
Answers to the do now:

3. What causes chemical and physical changes to occur in nature?
Enthalpy – The tendency in nature to change into a state of lower energy.
Any reaction that occurs will occur spontaneously if it leads to increased enthalpy.
Example: Exothermic reactions move to a state with lower energy. Why?
Exothermic reactions release some of the energy of the reactants.

4. What causes chemical and physical changes to occur in nature?
Entropy – The tendency in nature to change into a state of greater randomness or disorder.
The greater the disorder, the higher the entropy.
Why is higher entropy favored over less?
It is necessary for particles to collide in a specific way to maintain a specific order. On the other hand, there are many ways particles can collide to produce disorder. Therefore, entropy is easier.

5. Examples of entropy Physical changes – solid to liquid to gas.
Chemical changes – compounds have a greater amount of order than the free elements of which they are composed.
How can we identify whether the reactants or products have more entropy? Consider the following:
What kind of phase changes are occurring.
Generally the side of the equation with the greater number of molecules has the greater entropy.

6. Activity/Homework
Activity (IN CLASS) – Answer the questions on the worksheet you were given.
HW Review Book Pages Copy and answer #36-44