Substances exist in three possible phases such as solid, liquid and gas. Heating and cooling of some substances can transform it from one phase to another. Vaporization is the phase change that occurs when a liquid is transformed into the gas. Substances are requiring a specific amount of heat to undergo the physical changes necessary to switch the phases. The energy or heat consumed per unit mass during the vaporization of any liquid is known as the heat of vaporization or sometimes known as enthalpy of vaporization. This article is explaining the concept of the heat of vaporization formula with examples. Let us learn it!
Concept of the Heat of Vaporization
To condense the water vapor into its liquid phase, we need to remove the energy from the gas. Also, it should be noted that the energy per unit mass needed to condense water vapor is equal to the heat of vaporization.
The heat of vaporization of water is the highest known value. Thus the heat of vaporization is the amount of heat that we need to turn one gram of a liquid into a vapor, without any rise in the temperature of the liquid.
Source:en.wikipedia.org
The units are calorie per gram and values for the heat of vaporization of water at different temperatures are used as standard. The heat of vaporization is a type of latent heat. Here, latent means to lie hidden or concealed. Therefore, latent heat is the additional heat needed to change the state of a substance from solid to liquid at its melting point.
What is Heat Vaporization?
In another way, the heat needed for changing from a liquid to gas states its boiling point. It is important to know that the latent heat is associated with no change in temperature, but a change of state. Because of the high heat of vaporization, evaporation of the water has a cooling effect and condensation has a warming effect.
Therefore, specifically, the heat of vaporization is the quantity of heat which is needed to be absorbed for the vaporization of a particular quantity of liquid at a constant temperature. If the solutions of vapor and liquid states are compared, then the kinetic energy of the steam is proved to be higher than the kinetic energy of the fluid.
When a liquid substance transforms into gas then it is vaporization. The vaporization process needs an increase in energy for allowing the liquid particles to overcome intermolecular attractions and vaporize. The amount of energy required is the heat of vaporization. The heat of vaporization is different for different substances but is a constant for each individual one.
The Formula for Heat of Vaporization
Based on entropy and enthalpy of the process of vaporization, the Heat of vaporization formula is:
\(H_v = \frac{ q } {m}\)
\(H_v\) | heat of vaporization |
q | Heat |
m | mass |
Solved Examples for Heat of Vaporization Formula
Q.1: If the heat of vaporization for water is 2257 joule per gram. Then, calculate the amount of heat energy that we need to apply to vaporize 145 grams of water. Use Heat of Vaporization Formula.
Solution: Given parameters are,
\(H_v\) = 2257 joule per gram
M = 145 grams
Now, rearranging the heat of vaporization equation as:
\(q = H_v \times m\)
i.e. \(q = 2257 \times  145\)
Therefore q = 327.265 KJ
Typo Error>
Speed of Light, C = 299,792,458 m/s in vacuum
So U s/b C = 3 x 10^8 m/s
Not that C = 3 x 108 m/s
to imply C = 324 m/s
A bullet is faster than 324m/s
I have realy intrested to to this topic
m=f/a correct this
Interesting studies
It is already correct f= ma by second newton formula…