What is calorimetry? What is a calorimeter? Explain its principle and construction.

(N/A) Calorimetry is the branch of science that deals with the measurement of heat.
$A$ calorimeter is a device used to measure the amount of heat involved in a physical or chemical process.
Principle: The principle of calorimetry is based on the law of conservation of energy. In an isolated system (where no heat exchange occurs with the surroundings), the heat lost by a hot body is equal to the heat gained by a cold body. Mathematically, $\text{Heat lost} = \text{Heat gained}$.
Construction: $A$ calorimeter typically consists of a metallic vessel and a stirrer made of the same material, such as copper or aluminium. The vessel is placed inside a wooden jacket or box, which is filled with heat-insulating materials like glass wool or cotton to minimize heat loss to the surroundings. The outer jacket acts as a thermal shield. $A$ lid is provided with an opening to insert a mercury thermometer to measure the temperature changes during the experiment.