1. Mr. Quinn & Ms. Tom February 24, Aim: How do we determine where energy goes in a chemical reaction? Do Now:
List one reaction that increases the surrounding temperature, and one reaction the decreases the surrounding temperature.

2. The Laws of Thermodynamics
Energy cannot be created or destroyed
The disorder of a system increases over time

3. Endothermic Reactions
Two Types of Reactions
Exothermic Reactions
Temperature increases
Energy is released
Heat is a product
Endothermic Reactions
Temperature decreases
Energy is absorbed
Heat is a reactant

4. Example 1

5. Example 1
Did the temperature of the surroundings increase or decrease?
INCREASE
Is the reaction pictured exothermic or endothermic?
EXOTHERMIC
Provide one justification for your answer to the previous question.
TEMPERATURE INCREASED AND THERE WAS A FIRE
Where was the energy released to?
THE AIR
Would you predict that the products have a higher or lower energy than the reactants?

6. Example 2

7. Example 2
Did the temperature of the surroundings increase or decrease?
DECREASE
Is the reaction pictured exothermic or endothermic?
ENDOTHERMIC
Provide one justification for your answer to the previous question.
TEMPERATURE DECREASCED
Where was the energy absorbed from?
THE WATER
Would you predict that the products have a higher or lower energy than the reactants?

8. Let’s Try It Out!
Melting ice causes the temperature of the air to DECREASE. Is the process of melting exothermic or endothermic? Why?
When water vapor forms snow (deposition), the temperature of the air INCREASES. Is deposition exothermic or endothermic? Why?

9. Let’s Try It Out!
Dissolving table salt in water is endothermic. What do you expect to happen to the temperature of the water?
Burning Mg creates a hot white flame. Is this process exothermic or endothermic? Explain.

10. Let’s Try It Out!
A process is exothermic. Is energy a product or reactant? 
A process leaves products with less energy than the reactants. Is it exothermic or endothermic?

11. Your Turn!