Understanding Heat in Chemical Reactions: Thermodynamics & Energy Changes

1. Objectives: • To be able to: • See where heat is a part of any chemical reaction

2. Homework • Formal Lab Report due Wednesday 5/25 on Turn It In.com • Complete Worksheet

3. Definitions • Thermodynamics • The study of how heat and other forms of energy are involved in a chemical reaction • Enthalpy • The stored energy in a substance

4. Types of Chemical Reactions • Exothermic • A reaction that releases heat • The enthalpy of the system decreases • Endothermic • A reaction that absorbs heat • The enthalpy of the system increases

7. Heat Energy Changes • When a chemical reaction takes place bonds are broken and new bonds form • Breaking bonds require energy input • Endothermic • Forming bonds release energy • Exothermic • The net change depends on the ratio of heat absorbed and heat released during the breaking and making bonds

8. More about the Bump • Activation energy • The amount of energy needed to initiate the chemical reaction

9. Catalyst • Catalyst • Any compound that speeds up a chemical reaction without it self being changed • It lowers the activation energy of the reaction

10. Catalyst