1. Warm-Up 3/19/14
Balance these equations!

2. Heat and Chemical Reactions
3/19/14

3. Energy in Reactions Energy is stored in chemical bonds This means…
Bonds can be hard to break!

5. Breaking & Forming Bonds
Step 1: Energy must be SUPPLIED to break chemical bonds
Step 2: Energy is RELEASED when new chemical bonds are made

6. Two Main Categories Exothermic Endothermic
More energy is RELEASED than SUPPLIED
Heat “exits”
Example: combustion
More energy is SUPPLIED than is RELEASED
Heat “enters”
Example: photosynthesis, ammonium nitrate + water

7. Reaction Coordinate Diagram
Shows stored energy of reactants and products
Hump=where reaction is happening
∆E=overall change in energy after reaction occurs

9. Represented by Equations
Enthalpy is heat energy.
The change in heat energy during a chemical reaction is represented with ∆H.
∆H = E of products – E of reactants

10. Combustion!
Example

11. Negative ∆H = exothermic (energy lost when creating products)
Positive ∆H = endothermic (energy gained when creating products)

12. Try It! Exothermic or Endothermic?

13. Your Job
Complete the practice problems on the back of your notes for tomorrow
Tomorrow: Balancing Equations QUIZ
Test on Tuesday next week