Calorimetry

In <a href="/facts/Chemistry/SrNqkGVm">chemistry</a> and <a href="/facts/Thermodynamics/q4hIx3yP">thermodynamics</a>, calorimetry is the science or act of measuring changes in <a href="/facts/State_variables/HNF1dCXu">state variables</a> of a body for the purpose of deriving the <a href="/facts/Heat_transfer/1IV3WbFL">heat transfer</a> associated with changes of its <a href="/facts/Thermodynamic_state/Rv6m11Pf">state</a> due, for example, to <a href="/facts/Chemical_reaction/GpqWlKrz">chemical reactions</a>, <a href="/facts/Physical_change/kfzhe7M3">physical changes</a>, or <a href="/facts/Phase_transition/eLP2BY8R">phase transitions</a> under specified constraints. Calorimetry is performed with a <a href="/facts/Calorimeter/Njp46oI8">calorimeter</a>. Scottish physician and scientist <a href="/facts/Joseph_Black/0HD6fdYR">Joseph Black</a>, who was the first to recognize the distinction between <a href="/facts/Heat/e9QqQ0B2">heat</a> and <a href="/facts/Temperature/QyGe4gmj">temperature</a>, is said to be the founder of the science of calorimetry.
<a href="/facts/Indirect_calorimetry/Ir8UyXQN">Indirect calorimetry</a> calculates heat that living organisms produce by measuring either their production of <a href="/facts/Carbon_dioxide/xGzpppEp">carbon dioxide</a> and nitrogen waste (frequently <a href="/facts/Ammonia/MtLtJFtz">ammonia</a> in aquatic organisms, or <a href="/facts/Urea/6j84AoCG">urea</a> in terrestrial ones), or from their consumption of <a href="/facts/Oxygen/acyn6o8r">oxygen</a>. <a href="/facts/Antoine_Lavoisier/UheVQrhu">Lavoisier</a> noted in 1780 that heat production can be predicted from oxygen consumption this way, using <a href="/facts/Multiple_regression/n6z5Tf7K">multiple regression</a>. The <a href="/facts/Dynamic_energy_budget/8EC1Vkjo">dynamic energy budget</a> theory explains why this procedure is correct. Heat generated by living organisms may also be measured by direct calorimetry, in which the entire organism is placed inside the calorimeter for the measurement.
A widely used modern instrument is the <a href="/facts/Differential_scanning_calorimeter/Gj9u8Plc">differential scanning calorimeter</a>, a device which allows thermal data to be obtained on small amounts of material. It involves heating the sample at a controlled rate and recording the heat flow either into or from the specimen.

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Calorimetry