Question

How much heat is required to convert steam of $100^\circ $ to water of $100^\circ $?

Answer 1

Hint: Latent heat of vaporization is the amount of heat required to change the state of a boiling liquid to gas.
The latent heat of vaporization of water is $2260kJk{g^{ - 1}}$

Complete answer:
The latent heat of vaporization for a liquid is the amount of heat required to convert a unit mass of that liquid into vapor without a temperature change. The latent heat absorbed by the body is utilized to overcome the intermolecular attraction thus changing its phase but since the whole heat is utilized in overcoming the intermolecular attraction thus no change is observed in the temperature of the substance
Now since some amount of heat was given to water at $100^\circ C$to transform it to steam or to change its state. So now if we want to reverse this process and again convert heat into steam, we should take back the energy we gave to it for changing its phase from water to steam .So, the amount of heat supplied for the phase change is given by
$Q = mL$
Where Q is the heat supplied m is the mass and L is the latent heat
Since here no mass is given so we will take the general case so, the mass will be taken as 1kg
Therefore, here we need to remove the heat not supply heat because we are reversing the process in which heat was given or supplied to convert water into vapor
So, the amount of heat needed to be removed will be $Q = 1 \times 2260 = 2260kJ$
So $2260kJ$ energy will be removed not supplied to convert back the steam at $100^\circ C$to water at $100^\circ C$
Final Answer: $2260kJ$ energy will be removed not supplied to convert back the steam at $100^\circ C$to water at $100^\circ C$

Note:
To change the state of matter from solid to liquid, liquid to gas or solid to gas the energy is supplied for conversion or phase change
TO convert gas back to liquid or liquid back to solid the energy is removed not supplied
Sensible heat causes a rise in temperature whereas latent heat changes the phase.