1. Chapter 16 Chemical Reactions That Involve Heat

2. The study of the changes in heat in chemical reactions. Thermochemistry

3. Chemical Reactions Involve ENERGY Changes in ENERGY result from bonds being broken and new bonds being formed.

4. Requires ENERGY Breaking Bonds

5. Releases ENERGY Bond Formation

6. Both absorption and release of energy occurs. In a chemical reaction We detect the net result. Measure the temperature of the surroundings.

7. System: Reactants and Products System & Surroundings Surroundings: Solvent, container, atmosphere above the reaction, etc.

8. Types of Reactions

9. RELEASE HEAT! Exothermic Reactions C 3 H 8 (g) + 5O 2 (g) 3CO 2 (g) + 4H 2 O (g) + 2043 kJ Combustion reactions are exothermic! HEAT is listed as a product in the reaction! HEAT ENERGY

10. Exothermic Reactions Energy needed to break bonds must be LESS THAN the energy released when new bonds are formed. Surroundings will have a higher temperature after the reaction!

11. NaOH (s) Na + (aq) + OH - (aq) Beginning Temp of Surroundings: 25.4 ° C Ending Temp of Surroundings: 29.5 ° C Change in Temp of Surroundings: +4.1 ° C +4.1 ° C Means heat was GIVEN OFF EXOTHERMIC

12. NaOH (s) Na + (aq) + OH - (aq) +4.1 ° C Calculate HEAT per MOLE if you have 5.0 grams of NaOH to start. 5.0 g NaOH 40 g NaOH 1 mol NaOH 0.125 mol NaOH = +4.1 ° C 0.125 mol NaOH = + 33 ° C per mole NaOH Means HEAT is given off.

13. ABSORB HEAT! Endothermic Reactions C (s) + H 2 O (g) + 113 kJ CO (g) + H 2 (g) HEAT is listed as a reactant in the reaction! HEAT ENERGY

14. Endothermic Reactions The energy needed to break bonds is GREATER THAN the energy released when new bonds are formed. Surroundings will have a lower temperature after the reaction!

15. Exo & Endo Demos

16. Fireworks

17. More about fireworks