If we focus on the field of physics, the hot It is the energy that is transferred from one body to another, capable of generating a change of state and the dilation of these bodies. Latent , on the other hand, is that which is hidden or seems inactive.
The notion of latent heat refers to the heat that, when received by a body , does not increase its temperature , but is used to produce a status change .
It is important to note that the temperature is the physical magnitude which is responsible for expressing the level of heat. In the case of latent heat, therefore, it is energy that does not increase that magnitude in the body.
It can be said that latent heat is the energy that a body or substance requires to change its state . A substance in a liquid state, for example, needs a certain latent heat to enter a gaseous phase. In this context the latent heat can be called evaporation heat . In a similar sense, a solid substance requires latent heat to enter a liquid state: the heat of fusion .
As heat does not translate into a variation in temperature while the change of state, seems to be hidden . That is why there is talk of latent heat, since heat is added to the substance without changing its temperature.
The use of this concept to describe the phenomenon that is observed when a body or substance changes state without the heat applied affecting its temperature derives from a remote time in which scientists believed that heat was a fluid substance, and called it caloric.
This responds to a model called caloric theory, which at the time served to explain for a long time the behaviors and physical traits of heat, understanding it as a fluid, which was said to permeate the matter and was the cause of his heat.
When heat is applied to a substance that does not register a change of state but does increase its temperature, experts refer to the sensible heat . It is worth mentioning that this is the way in which we understand heat in everyday speech, since we only attend to temperature variation.
With regard to sensible heat, most of the experiments carried out suggest that in order to affect the temperature of a given body we need to apply a quantity of heat directly proportional to its dough and to the delta of temperatures that we intend to reach.
To continue with the explanation of the concept of latent heat let's take, for example, an experiment through which we apply heat to a cube of ice ; given that the latter is at a temperature below 0 ° C, where the water had to change from a liquid to a solid state in the first place to obtain the ice piece, we must reach that threshold and cross it if we want to see the reverse process .
From the moment we reach 0 ° C and until the ice cube has been molten completely, its temperature will not change. The reason for this interruption in the increase in heat is due to the principle set forth in the first paragraphs: latent heat is not used to affect body temperature, but to produce its fusion.
As expected, once the piece of ice has melted, the water temperature will begin to rise until it reaches the next state change point, which in this case is 100 ° C, where again the temperature will remain stable until all the substance is evaporate .