1. 4/10/12 - Bellringer Explain what is happening at a molecular level when energy is added or removed.

2. Grade Worksheets

3. 23.4 – Reaction Rates and Energy Part A

4. Objectives Identify the source of energy changes in chemical reactions. Compare and contrast endothermic and exothermic reactions.

5. Chemical Kinetics The area of chemistry concerned with the speed at which reactions occur

6. Collision Theory In order for reactants to form products the reactants must collide with enough energy to start the reaction (activation energy)

7. Energy Changes Chemical reaction involve energy exchange –Breaking chemical bonds requires energy –Forming chemical bonds releases energy

8. More Energy Out In exergonic reactions, the energy required to break bonds is less than the energy released from new bonds –The energy given off is usually light Exergonic - releases more than absorbs

9. Exothermic Reaction Give off energy in the form of heat

10. More Energy In In endergonic reaction, more energy is required to break bonds than to form new ones, energy is needed for the reaction to occur Endergonic – absorbs more than releases

11. Endothermic Reaction If the energy needed/absorbed is heat

12. In-Class Assignment/Homework 23.3+4 DR WKT 23.4 RFN WKT –#2, 4, 10-13 ONLY