Calorimetry: Class 11 Physics Notes, Definition, Working Principle, & Types

Calorimetry means the measurement of heat during a chemical or physical process. The heat measurement is done using a device called a calorimeter. There are five types of calorimeters. 

The definition of Calorimetry as per the NCERT textbook is, “A device in which heat measurement can be done is called a calorimeter”. 

Explanation: Calorimetry means heat measurement. 

Example: When a body with a high temperature is placed near the body with low temperature. Then the heat lost by the hot body is equal to the heat gained by the cold body. During this process no heat escaped in the surrounding. Here, we use calorimetry to measure the heat transfer. 

Importance of Calorimetry 

Calorimetry is important in identifying the thermal properties of heat transfer during a chemical reaction or physical changes, such as heat capacity, enthalpy, and stability.

The main function of calorimetry is to measure the heat produced or destroyed during a chemical or physical change. A calorimeter is based on the principle of energy conservation. 

Construction of Calorimetry 

• A metallic vessel and stirrer (copper or aluminium) are placed in a wooden jacket. 

• The insulating jacket (wooden jacket) consists of insulation material such as glass, wool, etc.  

• The outer part of the wooden jacket prevents the loss of heat. 

• A mercury thermometer is inserted into the calorimeter through an opening in the outer jacket.  

Heat Exchange Principle (Law of Mixtures)  

Heat moves from the hotter to the cooler substance when two substances of different temperatures are mixed until thermal equilibrium is achieved. The temperature at which this equilibrium is reached is known as the final temperature of mixture. 

The heat gained by the cooler substance equals the heat lost by the warmer one: 

[ m1 s1 (T1 - Tm) = m2 s2 (Tm - T2) ] 

Where: 

• (m1, m2) are the masses of the substances, 

• (s1, s2) are their specific heat capacities, 

• (T1, T2) are their initial temperatures, 

• ( T_m) is the final equilibrium temperature. 

Thermodynamics' Zeroth Law: According to this law, two systems (A and B) are in thermal equilibrium with one another if they are also in thermal equilibrium with a third system (C). The idea of temperature is based on this principle 

The most common types of calorimeters are: 

• Differential scanning calorimeter 

• Accelerated rate calorimeter 

• Isothermal micro calorimeter 

• Bomb Calorimeter 

• Reaction calorimeter