1. Thermodynamics Unit 10

2. Endothermic vs. Exothermic Endo – chemical absorbs or takes in energy or heat Exo – chemical produces or gives off energy or heat Remember BARF!

3. Chemical Energy Change: Endo – increases, chemical gains PE Exo – decreases, chemical loses PE Endothermic vs. Exothermic

4. Thermal Energy Change of Surroundings: Endo – decreases, surroundings (often H 2 O) lose KE Exo – increases, surroundings (often H 2 O) gain KE

5. Temperature of Surroundings (often H 2 O or solution): Endo – decreases Exo - increases

6. Energy Transformation Endo – thermal  chemical KE  PE Exo – chemical  thermal PE  KE Endothermic vs. Exothermic

7. Examples: Endo – melting, boiling, evaporation, cold pack Exo – burning, explosions, freezing, condensation, hot pack

8. Model Chemical could be ice or other substance H 2 O represents surroundings Endothermic vs. Exothermic

9. Endothermic Endothermic vs. Exothermic chemical H2OH2OH2OH2O T decreases heat

10. Exothermic chemical H2OH2OH2OH2O T increases heat Endothermic vs. Exothermic

11. Graphs of Potential Energy –Endothermic Endothermic vs. Exothermic PE Reaction Coordinate Reactants Products E in Note: Chemical E increasing

12. Graphs of Potential Energy –Exothermic Endothermic vs. Exothermic PE Reaction Coordinate Reactants Products E out Note: Chemical E decreasing

13.  H = Molar Heat 1.H represents: PE (heat content) of products or reactants a.k.a. “enthalpy” Endothermic vs. Exothermic

14. 2.  H is the change in heat content  H = H products – H reactants (Find  H by reading the PE graph.) Endothermic vs. Exothermic

15. 3. Endothermic products have more H, that means the molar heat is positive. 4. Exothermic products have less H, that means the molar heat is negative. Endothermic vs. Exothermic