Calorimetry is the
scienceof measuring the heatof chemical reactions or physical changes. Calorimetry involves the use of a calorimeter. The word calorimetry is derived from the Latin word "calor", meaning heat. Scottish physician and scientist Joseph Black, who was the first to recognize the distinction between heatand temperature, is said to be the founder of calorimetry.cite book|author= Laider, Keith, J.|title=The World of Physical Chemistry|publisher=Oxford University Press|year=1993|id=ISBN 0-19-855919-4]
Indirect calorimetry calculates
heatthat living organisms produce from their production of carbon dioxideand nitrogen waste (frequently ammoniain aquatic organisms, or ureain terrestrial ones), OR from their consumption of oxygen. Lavoisier noted in 1780 that heat production can be predicted from oxygen consumption this way, using multiple regression. The Dynamic Energy Budgettheory explains why this procedure is correct. Of course, 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.
Calorimetry is performed using one of two methods: constant volume or constant pressure, or constant mass.
"Constant-mass calorimetry" is a calorimetry performed at a constant
massand specific heat.
energy, or heat,:"m" is mass, :"c" is specific heat,:"ΔT" is change in temperature.
"Constant-volume calorimetry" is calorimetry performed at a constant
volume. This involves the use of a constant-volume calorimeter.
No work is performed in constant-volume calorimetry, so the heat measured equals the change in internal energy of the system. The equation for constant-volume calorimetry is (the heat capacity at constant volume is assumed to be constant):
:"ΔU" is change in
internal energy,:"ΔT" is change in temperatureand:"CV" is the heat capacityat constant volume.
Since in "constant-volume calorimetry" the
pressureis not kept constant, the heat measured does not represent the " enthalpychange.
"Constant-pressure calorimetry" is calorimetry performed at a constant
pressure. This involves the use of a constant-pressure calorimeter.
The heat measured equals the change in internal energy of the system minus the work performed:
Since in "constant-pressure calorimetry",
pressureis kept constant, the heat measured represents the " enthalpychange":
This formula is a simplified representative of
Accelerating rate calorimetry
Differential scanning calorimetry
Isothermal titration calorimetry
Thermodynamic databases for pure substances
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