Thermalchemical

Thermalchemical is an adjective used to describe aspects of thermochemistry, the branch of chemistry that studies the relationship between heat and chemical change. Thermalchemical phenomena include the absorption or release of heat during chemical reactions, the temperature dependence of reaction equilibria, and the heat capacities of substances. The central quantity is the enthalpy change of a process, ΔH, which at constant pressure equals the heat exchanged with the surroundings. Standard thermochemical data lists, for example, standard enthalpies of formation, combustion, and reaction enthalpies under specified conditions (usually 25°C and 1 atm).

Key concepts and methods in thermalchemical study include calorimetry and the use of thermochemical tables. Calorimetry measures heat changes: bomb calorimetry for combustion processes and coffee-cup calorimetry for solution-phase reactions. Differential scanning calorimetry (DSC) provides information on heat flow during heating or cooling, including phase transitions and heat capacities. Foundational principles include Hess's law, which states that total enthalpy change is path-independent, and Kirchhoff’s law, describing how reaction enthalpies vary with temperature based on heat capacities.

Applications of thermalchemical data span industrial chemistry, energy calculations, materials science, environmental chemistry, and food science. Accurate enthalpy data support process design, safety analysis, and modeling of chemical systems under varying temperatures. While the term thermalchemical is sometimes used interchangeably with thermochemical, the more common usage in scientific literature is thermochemical or thermochemistry to denote the field, data, and processes related to heat and chemical change.