Calorimeter

A calorimeter is a device used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber. It is one of the measurement devices used in the study of thermodynamics, chemistry, and biochemistry.

To find the enthalpy change per mole of a substance

A

{\displaystyle A}

in a reaction between two substances

A

{\displaystyle A}

and

B

{\displaystyle B}

, the substances are separately added to a calorimeter and the initial and final temperatures (before the reaction has started and after it has finished) are noted. Multiplying the temperature change by the mass and specific heat capacities of the substances gives a value for the energy given off or absorbed during the reaction. Dividing the energy change by how many moles of

A

{\displaystyle A}

were present gives its enthalpy change of reaction.

q

=

C

v

(

T

f

−

T

i

)

,

{\displaystyle q=C_{\text{v}}(T_{f}-T_{i}),}

where q is the amount of heat according to the change in temperature measured in joules and Cv is the heat capacity of the calorimeter which is a value associated with each individual apparatus in units of energy per temperature (joules/kelvin).

History

In 1761 Joseph Black introduced the idea of latent heat which led to the creation of the first ice calorimeters. In 1780, Antoine Lavoisier used the heat released by the respiration of a guinea pig to melt snow surrounding his apparatus, showing that respiratory gas exchange is a form of combustion, similar to the burning of a candle.