Endothermic and Exothermic Reactions

Endothermic reactions 
the reactants have less potential energy than do the products. Energy must be input in order to raise the particles up to the higher energy level.

Exothermic reactions

the reactants have more potential energy than the products have. The extra energy is released to the surroundings.



Enthalpy (H)
The heat contained in the system.
ΔH = H product - H reactant

Activation Energy
The Energy required to initiate a chemical reaction. Both endothermic and exothermic reactions require activation energy.

                                   ENERGY DIAGRAM