Estimation of Quantity of Heat
The quantity of heat transferred by some process can either be directly measured, or determined indirectly through calculations based on other quantities.
Direct measurement is by calorimetry and is the primary empirical basis of the idea of quantity of heat transferred in a process. The transferred heat is measured by changes in a body of known properties, for example, temperature rise, change in volume or length, or phase change, such as melting of ice.
Indirect estimations of quantity of heat transferred rely on the law of conservation of energy, and, in particular cases, on the first law of thermodynamics. Indirect estimation is the primary approach of many theoretical studies of quantity of heat transferred.
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