Latent heat is a form of energy, defined as the hidden or unseen type of energy. It is the heat transformation that takes place during the thermodynamic process of a mass where the particular energy is absorbed or released. The main drive of the process involves a constant-temperature operation that can also be claimed as a first-order phase transition. By keeping the temperature constant, it is provided or extracted to modify the state of a substance (physical state). The process of condensation or evaporation at a certain temperature and pressure leads to the latent heat of vaporisation and fusion, the two examples of latent heat energy. Joseph Black, the British chemist in 1762, coined the term “latent heat.”

Dimensional Formula: 

The Dimensional Formula of any bodily amount is defined as the expression that represents how and which of the bottom portions are protected in that amount. It is denoted through enclosing the symbols for base portions with suitable strength in rectangular brackets, i.e. [ ].

An example is the Dimension Formula of Mass which is given as (M). 

Example

Let’s take the formula of speed.

Speed = Distance / Time

The distance can be written in length [L]

Time can be written as [T]

The dimensional formula would be [ M0 L1 T-1]

Hence, we can conclude that the speed is dependent on only length and time, not mass.

Dimensional equation

To get the dimensional equation, the physical quantity is equated with the dimensional formula. 

Example

Velocity = [ M0 L1 T-1]

Here, velocity is the physical quantity, which is equated to the dimensional formula.

Here is the list of various physical quantities and their dimensions.

Dimensional formula of Latent Heat

The dimensional formula of latent heat can be written as:

[M0L2T-2]

Where,

M = Mass

L = Length

T = Time

Derivation for the formula of latent heat can be expressed as:

Latent heat = (Heat). 1 / (Mass) …(i)

• The dimensional formula of mass can be written as [M1L0T0] …(ii)

Note:The dimensions of heat can be written as the dimensions of energy or dimensions of work

• Work = (force).(displacement) …(iii)

Note: The dimensional formula of the following quantities are:

• Displacement = [M0L1T0] …(iv)

• Force = [M1L1T-2] …(v)

By putting the values of equations (iv) and (v) in equation (iii).

Work = [M1L1T-2].[L1]

Therefore, the final dimensional formula of work or heat = [M1L2T-2] …(vi)

By putting the values of equations (ii) and (vi) in equation (i) 

We finally conclude the dimensional formula of the latent heat

• I.e. Latent heat = (Heat). 1 / (Mass)

Therefore, L = [M1L2T-2]. [M1L0T0]-1 = [M0L2T-2].

Hence, the dimensional formula of latent heat can dimensionally be represented as

[M0L2T-2].

Latent Heat meaning

Latent stands for hidden because this heat is not getting manifested externally as a rise in temperature. We call this heat latent heat or hidden heat. There was a change of state from ice to water or from water to vapour the heat energy that was observed was not completely manifested. A similar thing will happen if water freezes into ice or water condenses into water. The heat that will be liberated will not be externally manifested as any rise or fall in temperature.

Conclusion:

Latent heat is a form of energy that is absorbed or released and takes place during the thermodynamic process of the substance. The form of energy is said to be unseen or hidden. The latent heat works on the principle of constant temperature operations where there may be fluctuation in other physical factors, but the temperature is kept constant throughout. The latent heat of vaporisation is when the liquid turns into gas, whereas the latent heat of fusion occurs during the solid-state transition to liquid. The specific latent heat is the energy calculation required for phase transformation; it is based on mass and mole differently.