Termochimico

Termochimico (thermochemistry) is the branch of chemistry that studies the energy changes associated with chemical reactions and physical processes. It focuses on heat transfers that occur during chemical transformations, typically measured at constant pressure, and on how these exchanges relate to fundamental thermodynamic quantities such as enthalpy, heat capacity, and entropy.

Key concepts include the enthalpy change, ΔH, which represents the heat absorbed or released under constant pressure. Reactions are classified as exothermic when they release heat (ΔH < 0) and endothermic when they absorb heat (ΔH > 0). Calorimetry is the experimental method used to determine these heat changes. Bomb calorimeters are used for combustion and other processes at constant volume, while constant-pressure calorimeters measure q_p directly. Differential scanning calorimetry can study phase transitions and heat capacity as a function of temperature.

Thermochemistry is closely linked to thermodynamics. The enthalpy change relates to the internal energy change ΔU through ΔH = ΔU + PΔV, and the study often employs Hess's law to determine ΔH for reactions by combining known formation enthalpies. Standard molar enthalpies of formation, ΔH_f°, furnish a practical way to estimate ΔH for many reactions, and bond enthalpies provide another approximation. Temperature dependence is described by heat capacities and, more broadly, by temperature-dependent functions of enthalpy and entropy.

Applications span chemical manufacturing, energy production, material science, and biochemistry, including combustion analysis, battery chemistry, and the study of phase transitions. Thermochemistry provides the quantitative framework for predicting reaction feasibility, optimizing processes, and interpreting calorimetric data.