1. 14.3 Energy and Reactions

2. Energy and Reactions Energy is involved in chemical reactions…
to break bonds in the reactants
AND
2. to form new bonds to make new products

3. Endothermic Reactions
Endothermic reaction: forming new bonds requires energy
endo = energy “in”
Endothermic reactions will get colder.

4. Examples of Endothermic Reactions
Photosynthesis:
Cold packs:

5. Exothermic Reactions exo = energy “exits”
Exothermic reaction: forming new bonds releases energy
exo = energy “exits”
Exothermic reactions will get hotter.

6. Check in! Classify each as endothermic or exothermic:
When activated, a cold pack gets colder
A fire gives off heat
A candle burns
Endo, Exo, Exo

7. Activation Energy
Activation energy: the energy needed to begin a reaction and break chemical bonds in the reactants
Example:

8. Reaction Coordinate Diagram
Show the energy changes throughout a reaction
Activation Energy
Energy
Products
Energy change for the reaction
Reactants
Reaction progress

9. Reaction Coordinate Diagram
Endothermic reactions require energy
-Higher energy after reaction than before
Exothermic reactions give off energy
-Lower energy after reaction than before

10. Potential Energy
Is this an example of an endothermic reaction or an exothermic reaction?