Flexi Says: Heat changes in chemical reactions are most often measured in the laboratory under conditions in which the reacting system is open to the atmosphere. In that case, the system is under constant pressure. Enthalpy (H)
is the heat content of a system at constant pressure. Chemists routinely measure changes in the enthalpy of chemical systems as reactants are converted into products. The heat that is absorbed or released by a reaction at constant pressure is the same as the enthalpy change and is given the symbol ΔH
. Unless otherwise specified, all reactions in this material are assumed to take place at constant pressure.
