1. Unit 4 lec 3 Final model
Go back to your energy model #1 paper and complete your final model.
Remember the model is meant to show what would happen if you take two equal amounts of water, one at 00C and one at 1000C and mix together.
Remember models both show what happens and explain WHY!
Once you are done explain your model to your group partners!

2. Unit 4: Energy and Thermodyamics
PS 1-4 Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy

3. At the beginning of the reaction there are reactants with certain energy

4. In order for the reaction to occur Activation Energy needs to be reached.
Activation energy (Ea) = minimum amount of energy to start a reaction.
The more energy needed to start a reaction, the higher the activation energy.

5. At the end of the reaction there are products with certain energy

6. } ∆H = difference in energy of reactants & products DH Time
Time vs. energy
Energy }
Reactants DH
Products
Time
- If ΔH is positive the reaction is Endothermic
- If ΔH is negative the reaction is Exothermic

7. Exothermic vs. Endothermic

8. For example… The evaporation of water
H2O (l)  H2O (g)
Does this reaction require a little or a lot of energy to start?
Does this reaction have a positive or negative ΔH?
Is this reaction exothermic or endothermic?

9. For example… The formation of NH3
N2 + 3H2  2NH3
Does this reaction require a little or a lot of energy to start?
Does this reaction have a positive or negative ΔH?
Is this reaction exothermic or endothermic?