CHEMISTRY GUIDE

Topic 2.1 ENTHALPY CHANGES 1. Exothermic and endothermic reactions When a chemical reaction takes place, the products and reactants have different stabilities and thus there is a change in potential energy. However since total energy is always conserved, any change in potential energy must be balanced by an equal and opposite change in kinetic energy. The lower the chemical potential energy of a given chemical species, the more stable it is . This means that stable species have a lower potential energy than unstable species. In some reactions, the products are more stable than the reactants. The products therefore have less potential energy than the reactants, and the potential energy of the reacting species decreases. Since the total energy is always conserved, it follows that the kinetic energy of the species must increase. The particles thus move faster and the temperat...