Kalorimetere

Kalorimetere are instruments used to measure heat exchanged during chemical reactions or physical processes. They provide quantitative data about reaction enthalpies, phase transitions, and heat capacities. The term is used in several languages for the device commonly known in English as a calorimeter. Calorimetry relies on measuring a temperature change in a system with a known heat capacity, allowing the calculation of the heat flow q in joules or calories.

Principle and measurement: If a reaction occurs inside a calorimeter of known heat capacity C, the heat released or absorbed by the reaction is q_rxn = -C ΔT, where ΔT is the temperature change. In constant-pressure calorimetry, q_rxn approximates the enthalpy change ΔH, while in constant-volume calorimetry, q_rxn equals ΔU. Calorimeter constants are determined by calibration with known reactions or standard substances.

Types: Bomb calorimeter is used for combustion at constant volume, typically underwater in a water bath. A coffee cup calorimeter is a simple, constant-pressure setup made from Styrofoam cups. Differential scanning calorimeter (DSC) measures heat flow as a function of time or temperature during controlled heating or cooling, useful for studying phase transitions and crystallinity. Isothermal and other adiabatic calorimeters are used for sensitive or long-duration measurements. Each type has distinct sensitivity, heat capacity, and isolation from environmental heat exchange.

Applications: Calorimeters are employed to determine heats of formation, combustion, and solution; to measure the energy content of foods; to analyze material and polymer thermal properties; and to study metabolic or biological processes in microcalorimetry. They provide essential data for thermodynamics, chemistry, materials science, and nutrition.