What is Heat? 

The Best Introductory Guide


written by Stanley Udegbunam || Dec 19, 2020

definition of heat



Heat is energy that is transferred from one body to another as a result of the difference in temperature.

If two objects with different temperatures are brought in contact, heat will be transferred across the objects.

The heat will flow from the object with a higher temperature to the object with a lower temperature.

Heat can also be defined as the amount of thermal energy in a system.

Thermal Energy is the energy obtained from the vibration of atoms and molecules of a substance due to its rise in temperature.

Heat is an extensive property because it is proportional to the total energy of all atoms in an object.

Heat capacity is the amount of heat required to raise the temperature of a body by 1 Kelvin.

It depends upon the mass of the material so it’s also an extensive property.

If there is a change in temperature of a substance without a change in phase, it is called sensible heat.

heat in science (thermal energy)


Latent heat is the energy absorbed by or released from a substance during a phase change.

Latent heat is also called hidden heat because the heat absorbed or lost is used to either break or form bonds.

As a result of this, there’s no increase or decrease in temperature.

In otherwords, a substance might transform from one phase to another without a change in temperature.

A typical example is the melting of ice at 0 degree Celcius to liquid at 0 degree celcius.

Similar to the vaporization of liquid at 100 degree celcius to steam at 100 degree celcius.

Generally, an increase in temperature corresponds to an increase in the kinetic energy of the molecules.

But for an ideal phase change, there is no corresponding increase in kinetic energy of the molecules.

Latent heat of fusion is the thermal energy required for an object to change from the solid-state to the liquid state and vice versa.

While latent heat of vaporization is the thermal energy required for a liquid to vaporize to a gas or the heat released when a gas condenses to liquid.

Heat is transferred either through conduction, convection, radiation or a combination of any.


The S.I unit of heat is Joule.

Calorie is also a unit of heat energy but it is not the S.I unit.

1 cal = 4.186 J


Heat is the energy that is transferred from one body to another as a result of temperature differences.

Heat always flows from objects of higher temperature to objects of lower temperature.

While latent heat refers to changes in phases without a change in temperature, sensible heat is the change in temperature without a change in phase.

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