1. 14.3 Energy and Reactions

2. Energy and Reactions
Energy is involved in chemical reactions in two ways:
to break bonds in the reactants so the atoms can form new bonds
AND
2. to form new bonds to make new products.

3. Endothermic Reactions
endo = energy “in”
endothermic reaction: uses more energy to form new bonds than it releases
Endothermic reactions will get colder.

4. Examples of Endothermic Reactions
Photosynthesis:
Cold packs:

5. Exothermic reactions will get hotter.
exo = energy “exits”
exothermic reaction: forming new bonds releases more energy than breaking old bonds
Exothermic reactions will get hotter.

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

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

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