1. Heat Exchange During Chemical Reactions Ms. Pittman Mathematics & Science Center

2. OBJECTIVES Use a calculator based laboratory system to collect and analyze lab data Monitor temperature changes during a chemical reaction Classify the reaction as endothermic or exothermic Calculate the change in enthalpy for the reaction (  H)

3. Chemical Reactions

4. “Clues” Precipitate forms (ppt) Gas evolved Heat released or absorbed

5. Enthalpy From the Greek word “enthalpein”. Denoted as “H”. Represents the heat content of a substance at a given temperature and pressure. Is a state function. Cannot be measured directly. Is an extensive property.

6. Formula:  H = H final - H initial  H = q p q = C m  T where C = 1 cal/g°C  H = “-” for an exothermic reaction  H = “+” for an endothermic reaction

7. Vinegar & Baking Soda

8. Endothermic or Exothermic? HC 2 H 3 O 2 (aq) + NaHCO 3 (s)  CO 2 (g) + H 2 O (l) + NaC 2 H 3 O 2 aq)

9. Tide Detergent and Water

10. Endothermic or Exothermic?

11. Post Lab Discussion