Explain the measurement of $\Delta U$ and $\Delta H$ by calorimetry.

(N/A) We can measure energy changes associated with chemical or physical processes by an experimental technique called calorimetry.
In calorimetry,the process is carried out in a vessel called a calorimeter,which is immersed in a known volume of a liquid.
Knowing the heat capacity of the liquid in which the calorimeter is immersed and the heat capacity of the calorimeter,it is possible to determine the heat evolved in the process by measuring temperature changes. Measurements are made under two different conditions:
$(i)$ at constant volume,$q_{v}$
$(ii)$ at constant pressure,$q_{p}$
$(a)$ $\Delta U$ measurements:
For chemical reactions,heat absorbed at constant volume is measured in a bomb calorimeter. Here,a steel vessel is immersed in a water bath. The whole device is called a calorimeter. The steel vessel is immersed in a water bath to ensure that no heat is lost to the surroundings.
$(b)$ $\Delta H$ measurements:
Heat absorbed at constant pressure is measured using a calorimeter (often a coffee-cup calorimeter). Since $\Delta H = q_{p}$,the heat change measured at constant pressure directly gives the enthalpy change of the reaction.