Question

What is the energy released by 20 grams of $100{}^\circ C$ steam that condenses
and then cools to $0{}^\circ C$?

Answer 1

A thermodynamic system's enthalpy is defined as the sum of the system's internal energy and the product of its pressure and volume. It is a state function that is employed in many chemical, biological, and physical tests under constant pressure, which is easily given by the vast ambient environment. The effort necessary to create the system's physical dimensions, i.e. to make space for it by displacing its surrounds, is expressed by the pressure–volume term.

Complete answer:
A chemical substance's molar heat capacity is the amount of energy that must be given to one mole of the material in the form of heat to induce a one-unit increase in temperature. It is also the specific heat capacity of the material times its molar mass, or the heat capacity of a sample of the substance divided by the amount of substance in the sample. The joule per kelvin per mole, or $J\cdot {{K}^{-1}}\cdot mo{{l}^{-1}}$ , is the SI unit for specific heat.
The energy was released as a result of two distinct processes: At $100{}^\circ C$ , the steam condenses, releasing some latent heat of condensation.
The water cools from 0 to 100 degrees Celsius without solidifying.
The amount of energy released in the first step is determined by the sample's mass and the ${{L}_{v}}$ latent heat of evaporation for water:
$\text{E(phase change)= m }\\!\\!\times\\!\\!\text{ }{{\text{L}}_{\text{v}}}\text{= 20g }\\!\\!\times\\!\\!\text{ 2,260J }\\!\\!\times\\!\\!\text{ }{{\text{g}}^{\text{-1}}}\text{= 45,200 J}$
The quantity of energy released in the second phase, on the other hand, is determined by the specific heat of water, the mass of the sample, and the magnitude of the temperature change.
$E(cooling)=m\cdot c\cdot \Delta T$
$E(cooling)=20g\cdot 4.2J\cdot {{g}^{-1}}\cdot {{K}^{-1}}\cdot (100K-0K)=8400J$
The total quantity of energy released is calculated by adding the energy changes of the two processes:
$E(released)=E(phase\text{ }change)+E(cooling)=53,600J=53.6kJ$

Note:
Phase transitions are the physical processes of transition between one state of a medium, identifiable by specific parameters, and another, with differing values of the parameters, in chemistry, thermodynamics, and many other related areas. Changes between the fundamental states of matter: solid, liquid, and gas, as well as plasma in rare circumstances, are commonly referred to as transitions. A phase of a thermodynamic system, for example, and states of matter both have uniform physical characteristics. Certain properties of a medium change, frequently discontinuously, during a phase transition as a result of changes in external circumstances such as temperature, pressure, or others.