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

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

3. 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!

4. 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

5. Net Release of Energy

6. 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

7. Net Absorption of Energy

8. 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

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

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

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

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

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

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

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

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

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

18. 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…