Thermodynamic enthalpy is a very important quantity since it offers insight into the amount of heat present in a particular thermodynamic system. The amount of heat present in the thermodynamic system is proportional to the amount of useful work that can be done by it. In a chemical reaction, the enthalpy of the reaction provides insight into the endothermic or exothermic nature of the reaction. It is denoted by the symbol ΔH.
Systems having low net energies tend to be more stable than systems having high net energies. This is where the concept of enthalpy is quite significant. For exothermic reactions, the reactants release energy into the surrounds to form a stable product. In endothermic reactions, the reactants absorb energy from the surroundings to meet the requirement for the activation energy. The reactants then undergo a chemical reaction to form a product with high potential energy.