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Latent heat

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Heat is the sensation that living beings feel when the temperature rises , this if we see it from the biological point of view . But also, this term is important in the field of physics , where it is seen as the energy that can be passed from one body to another, a transfer that is related to molecules and atoms . One type of heat that exists in this broad field of study is known as latent heat .

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What is latent heat?

Latent heat is the type of heat that a certain body receives, but that does not produce any type of increase in body temperature but is only used so that a change in the state of matter can be generated .

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  • Definition
  • Latent heat characteristics
  • Types
  • How to calculate latent heat
  • Formula
  • Units
  • How it differs from specific heat
  • Importance
  • Table
  • Other examples of latent heat

Definition

Latent heat is the type of heat that occurs when a substance does not change its temperature even though it is faced with thermal energy , however, it manages to modify the state of segregation . It is a physical magnitude that manages to provide information on the amount of thermal energy or heat that a substance needs to be able to receive or lose heat in order to change its state. This implies that there is a change from solid to liquid, from liquid to gas, and so on.

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Latent heat characteristics

Among the main characteristics that can be observed in latent heat, we mention the following:

  • Produces changes in the state of matter .
  • It does not increase the temperature of a certain body.
  • It is also called heat of evaporation .
  • It is part of the model known as caloric theory .
  • It is a type of heat that cannot be felt .

Types

There are several types of latent heat which are mentioned below:

  • Latent heat of fusion : this type of heat is based on fusion which is a physical process that occurs due to the transition that a substance undergoes when it goes from a solid to a liquid state . Then, this type of latent heat can be defined as the enthalpy change that arises from the absorption of energy, which can cause the substance to go from a solid to a liquid phase. This process is given thanks to the melting temperature and has a pressure of 1 atm or 101 325 kPa.
  • Latent heat of vaporization : it is known by the name of enthalpy of vaporization and refers to the amount of energy that needs to be added to a certain substance when it is in the liquid phase so that the transition to the gaseous phase can take place . It is related to the boiling point of a substance.
  • Latent heat of solidification : refers to the heat that is involved within the phase change when a substance goes from a liquid to a solid state . It is the opposite of the latent heat of fusion because the energy that is released to the outside is produced when the phase change is generated.
  • Latent heat of condensation : it occurs at the moment in which there is a change in a substance that goes from a gaseous state to a liquid , for example water vapor.

How to calculate latent heat

The latent heat can be calculated exactly using a formula in which it is established that the heat necessary to be able to make a certain substance change phase will depend on the type of phase change that is sought.

Formula

In order to calculate the latent heat in a substance, the following formula is used:

Q = m. L

Where

  • Q : refers to the amount of heat (cal or J)
  • m : indicates the mass (g or kg)
  • L : displays latent heat (cal / g or J / kg)

Units

The units used to represent latent heat are within the International System and are measured in Joules / Kilogram (J / kg). It can also be measured on some occasions using the cal / g or calories per gram .

How it differs from specific heat

The difference is that specific heat is the amount of heat that must be supplied to the substance or system so that it can increase its temperature and that also depends on the value of the initial temperature. On the other hand, latent heat is the energy that is needed to be able to make a change in the phase , in other words, the passage of a substance from solid to liquid or from liquid to gas.

Importance

The main importance of latent heat lies in the Earth’s atmosphere since it is the main factor that intervenes significantly in the formation of convection clouds and also participates in maintaining the stability or instability of the atmosphere.

Other examples of latent heat

  • Latent heat of vaporization : h lg = 2257 kJ / kg
  • From water : 334103 J / kg
  • From silver : 105 kJ / kg.
  • Latent heat of copper : 214 / kg at 1,083 ° C
  • Of the lead : 2.45 J / kg

Latent heat of condensation

The latent heat of condensation occurs at the moment in which the phase change of a substance occurs when it passes from a gaseous state to a liquid , for example, the process that occurs in water vapor . The value of the latent heat of condensation is the same as that of vaporization , but with the difference that it will have a negative value . It is important to mention that the higher the temperature, the more the heat of condensation will be reduced and in the same way the boiling point will increase .

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