Calorimetry

Definition

Calorimetry is the measurement of heat transfers. This process is carried out using devices called calorimeters.

A calorimeter is an isolated system, typically a thermally insulated chamber such as a thermos bottle or a calorimetric vessel, designed to prevent heat exchange with the surroundings. It is also tightly sealed with a lid to prevent any exchange of matter.

A simple calorimeter showing the main components

Calorimeters are used to determine the thermal properties of substances, particularly their heat capacity or the energy released during a reaction, by measuring temperature changes within the system. Heat transfer occurs solely inside the calorimetric container under atmospheric pressure.

In practice, to calculate the amount of heat, we use a calorimeter, which is based on the application of the zero principle in isolated system.

∑ Q i = 0 ā‰« Q cal + Q 1 + Q 2 = 0 ∑Q_i=0 >> Q_cal+Q_1 +Q_2=0
Q cal = C cal ( T f − T 1 ) Q_{cal}= C_{cal}( T_{f} -T_{1})
Q 1 = m 1 c 1 ( T f − T 1 ) Q_{1}= m_{1}c_{1}( T_{f} -T_{1})
Q 2 = m 2 c 2 ( T f − T 2 ) Q_{2}= m_{2}c_{2}( T_{f} -T_{2})
C cal ( T f − T 1 ) + m 1 c 1 ( T f − T 1 ) + m 2 c 2 ( T f − T 2 ) = 0 C_{cal}( T_{f} -T_{1})+ m_{1}c_{1}( T_{f} -T_{1})+m_{2}c_{2}( T_{f} -T_{2})=0
C cal = − ( m 1 c 1 ( T f − T 1 ) + m 2 c 2 ( T f − T 2 ) ) ( T f − T 2 ) C_{cal}=- {(m_{1}c_{1}( T_{f} -T_{1})+m_{2}c_{2}( T_{f} -T_{2}) )} over {(T_{f} -T_{2})}

When the specific heat of water is C = 1 cal /g.K, Ccal is equal š¯›¨š¯’†š¯’’ to the water equivalent, which is the mass of water that absorbs the same amount of heat absorbed by the calorimeter.