1. 7.3 Energy Changes In Reactions
Chemical energy is the energy stored in the chemical bonds of the substance.
Chemical reactions involve the breaking of chemical bonds in the reactants and the formation of chemical bonds in the products.
Energy is either released or absorbed.

2. Reactions that release energy…
are EXOTHERMIC
The energy is released to the surroundings.
The energy released as the products form is greater than the energy required to break the bonds of the reactants.
Combustion
Feels warm (or hot)!

3. Reactions that absorb energy…
are ENDOTHERMIC
The energy is absorbed from the surroundings.
More energy is required to break the bonds of the reactants than is released when the products form.
Vinegar + baking soda
Feels cool (or cold)!

4. In both exothermic and endothermic reactions…
The total amount of energy before and after the reaction is the same.
This principle is known as the Law of Conservation of Energy.