Calorimetry

Calorimetry is the science or technique of measuring the amount of heat involved in chemical reactions or physical changes. It relies on calorimeters, devices designed to minimize and measure heat exchange between the system and its surroundings. In calorimetric measurements, the heat transferred during a process is related to the temperature change of the surroundings and the heat capacity of the calorimeter, via q = CΔT, where C is the heat capacity. Depending on whether the process is measured at constant volume or pressure, q corresponds to changes in internal energy (ΔU) or enthalpy (ΔH). In a constant-volume setup such as a bomb calorimeter, qrxn = -qcal and qrxn ≈ -ΔU. In atmospheric conditions, qrxn ≈ -ΔH.

Common calorimeter types include bomb calorimeters for combustion calorimetry, differential scanning calorimetry (DSC) for phase transitions and thermal transitions in materials, and isothermal titration calorimetry (ITC) for studying molecular interactions. DSC tracks heat flow as temperature is systematically varied, revealing melting points, crystallization, and glass transitions. ITC directly measures heat evolved or absorbed during a binding event, yielding thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), and binding constant (K).

Applications span food science, chemistry, materials science, and biochemistry, aiding in reaction energetics, material characterization, and binding studies. Accurate results require calibration of the calorimeter’s heat capacity, correction for baseline heat losses, and careful consideration of sample size and heat exchanges with the environment.