Heat:
Heat is a type of energy that transfers from a hot body to a cold body when they come into contact.

Heat Capacity (S):
The amount of heat required to raise the temperature of a substance by one degree (1 °C or 1 °K) is defined as the heat capacity.

Specific heat capacity (s):
It is the amount of heat required to raise the temperature of unit mass of a substance through 1°C. Its S.I unit is J kg^-1 K^–1.

Calorimeter
A calorimeter is a device that can be used to measure heat. It is intended to prevent or reduce heat loss. Calorimeters are made up of a metallic vessel and a stirrer made of the same high thermal conductivity material, such as copper or aluminium. The vessel is protected from the elements by being enclosed in a wooden jacket lined with heat-insulating materials such as glass wool. The outer jacket serves as a heat shield, preventing heat loss from the inner vessel. The outer jacket includes a thermometer and a stirrer. The stirrer accelerates reactions and heat transfer.

Principle of Calorimetry:
If bodies of different temperatures are brought in thermal contact, the amount of heat lost by the body at a higher temperature is equal to the amount of heat gained by the body at a lower temperature, at thermal equilibrium, provided no heat is lost to the surrounding.
Heat lost by the solid = Heat gained by the liquid + Heat gained by the calorimeter

The amount of heat lost/gained by the substance of mass m and specific heat when its temperature rises or falls by ∆t is given by

∆Q = m s ∆t