Latent Heat of Water - Definition, Types, Formula , FAQs

In this article we will be discussing about, latent heat of water, specific latent heat of vaporization of water, latent heat of vaporization of water, how to increase the latent heat of vaporization, what is the latent heat vaporization value, latent heat of ice in calories, latent heat of water in calories, latent heat of steam in calories, example of latent heat.

Latent heat definition

Latent heat is defined as a heat which is emitted or absorbed by a substance during the change of phase and without a temperature change. Here the phase change is transition of liquid to solid or gas, transition of solid to liquid or gas, transition of gas to solid or liquid. Generally latent heat is represented in joules or calories in unit mass.

Also read -

• NCERT Solutions for Class 11 Physics
• NCERT Solutions for Class 12 Physics
• NCERT Solutions for All Subjects
  
  

Latent heat of water definition

As mentioned before latent heat is heat required for phase change without temperature change. Similarly, latent heat of water is heat required for phase change of water without change in temperature of water. Here phase change is transition of water to ice or vapor, ice to water or vapor. When there is transition of state from liquid to solid and gas to liquid, during that time heat will be released (exothermic). When there is transition of state from liquid to gas and solid to liquid, during that time heat will be absorbed (endothermic).

Generally latent heat of water is of two types:

• latent heat of fusion
• latent heat of vaporization

Formula to calculate latent heat

L=Q/M

Were Q is the heat quantity

M is the body mass

L is latent heat

This equation states that the amount of heat released or absorbed by the substance of mass M gives as latent heat. The latent heat unit is given by J/Kg

Also read :

• NCERT notes Class 11 Physics Chapter 11 Thermal Properties of Matter
• NCERT solutions for Class 11 Physics Chapter 11 Thermal Properties of Matter
• NCERT exemplar class 11 physics solutions chapter 11 Thermal Properties of Matter

Latent heat of fusion:

Latent heat of fusion refers to melting a solid and freezing a liquid without change in temperature. Here melting a solid, means melt a ice (transition of solid phase to liquid phase) and freezing a liquid means cools down a liquid to ice (transition of liquid phase to solid phase)

Example of latent heat of fusion (1 calorie = 4.186 J)

Consider 1kg of ice at zero-degree Celsius, the amount of heat required to melt the ice to water is latent heat of fusion of 1kg of water is equal to 79.5 Cal/g or 333.55 kJ/kg without change in temperature. Similarly, the reverse effect of this is solidification i.e. the amount of heat required for freezing the water to ice is the same as heat required to melt the ice to water but with negative sign. So, the energy radiated by water to become ice is the same as energy absorbed by ice to become water.

Latent heat of vaporization of water:

Latent heat of vaporization refers to boiling a liquid and condensing a gas without change in temperature. Here boiling a liquid means we are going to heat the water (transition of liquid phase to gas phase) and condensing a gas means we are going to cool or condense the evaporated water (transition of gas phase to liquid phase).

Example of latent heat of vaporization of water

Consider a bucket of water boiling at 100-degree Celsius, the amount of energy required to change water to vapor is 540 Cal/g. Similarly, the energy required to condense the vapor back to water is -540cal/g. So, the latent heat of vaporization of water is 2257 kJ/kg.

NCERT Physics Notes:

• NCERT Notes Class 11th Physics
• NCERT Notes Class 12th Physics
• NCERT Notes For All Subjects

Specific latent heat

Specific latent heat is defined as the amount of heat required for transition of one phase completely to another phase for a unit mass. The heat capacity of a particular substance depends upon the mass of that substance. But the specific heat capacity (s) does not depend on the mass of the substance. Specific heat capacity is defined as at constant pressure the amount of heat required to increase the temperature to 1-degree Celsius for 1gram of substance. Specific latent heat is represented in J/Kg. This can be given as to increase the temperature to 1-degree Celsius for 1gram of water, we require 4.186J of heat or 1calorie. To calculate the heat required for change in temperature we can use this equation

q=m×s×∆t

Were q is heat required

m is mass of substance

s is specific heat

∆t change in temperature

This equation cannot be used when transition of phase takes place. For example, transition from solid, liquid and gas phase. Because when the heat is increased or decreased it does not cause change in temperature.

Also check-

• NCERT Exemplar Class 11th Physics Solutions
• NCERT Exemplar Class 12th Physics Solutions
• NCERT Exemplar Solutions for All Subjects