1. Thermochemistry

2. Conservation of Energy
Whatever changes occur in energy from one type to another, the total amount of energy remains constant
Energy cannot be created or destroyed

3. Energy in Reactions
In every type of change, there is a change in energy
Energy change usually more noticeable in chemical changes
Energy, or heat, of a reaction is symbolized by H
H is the heat of the products minus the heat of the reactants

4. Exothermic
If reactants have more chemical energy than the products, then energy must be lost in reaction
2H2 + O2  2H2O + energy
This release in heat energy causes the substances to become hot
H is a negative number

5. What is the H for the reaction shown by the diagram?

6. Endothermic Reactions
If products have more chemical energy than reactants, energy must be absorbed
2NaCl + energy  2Na + Cl2
The absorption of heat causes substances to feel cold
H is a positive number

7. What is the H for the reaction shown in the diagram?

8. Activation Energy
Even though some reactions are exothermic it may still require a little energy to start it off
This starting energy is called ACTIVATION ENERGY

9. What is the activation energy of the reaction shown?

10. What is the activation energy of the reaction shown?