Energy and Chemical Change Chapter 8 Lesson 3 L. Gilmore modified from N. Craft Energy and Chemical Change

Chemical Reactions involve Energy Energy Produced: 1) Sound 2) Light 3) Movement of matter 4) Heat (most common)

How do you know? How do you know that a chemical reaction has occurred. Change in temperature Change in state of matter to a new substance Change in color Here’s an example: NaCl reaction- The making of Salt Stop! Where’s your Evidence!

Law of Conservation of Energy “Energy is neither created nor destroyed in chemical reactions” Energy changes form All energy in chemical reactions relates to chemical bonds Humans: digesting food Battery example: Initial energy stored in battery Light energy for flashlight

Net Release of Energy

Net Release of Energy Exothermic process: releases energy Reactants have MORE energy than products Reactants are LESS stable Will need to label: Activation Energy And Energy Released by Reaction Activation Energy: the energy reactants must overcome for the reaction to proceed

Net Absorption of Energy

Net Absorption of Energy Endothermic Process: absorbs energy Reactants have LESS energy than products. Reactants are MORE stable. Will need to label: Activation Energy And Energy Absorbed by Reaction

Notes from Video https://www.youtube.com/watch?v=L- G7pLufXAo Endothermic and Exothermic Reactions by Bozeman Science

White-Board Review Questions What type of reaction absorbs energy? Endothermic

White-Board Review Questions What type of reaction releases energy? Exothermic

White-Board Review Questions In an endothermic reaction, are the reactants or products more stable? Reactants are more stable

White-Board Review Questions In an exothermic reaction, are the reactants or products more stable? Products are more stable

White-Board Review Questions Which has a bigger Activation Energy, an endothermic reaction or an exothermic reaction? Endothermic

White-Board Review Questions Which type of reaction causes the products to be “hot”? exothermic

White-Board Review Questions How do you know a chemical change has occurred? Change in temp Change in color Change in substance.

White-Board Review Questions Give an example of energy that can be produced in a reaction. Sound Light Heat Movement of matter

White-Board Review Questions Which type of reaction do you think is more likely to occur “naturally” (without the help of scientists!) Be prepared to share why…