Heat, Sensible Heat, Latent Heat, Specific Heat

Heat:

It is defined as the energy transferred, without transferring of mass across the boundary of a system. This phenomena occurs because of temperature difference between system and surroundings.

• It is denoted by Q and expressed in Joule (J)

Heat can be transferred in 3 ways

1. Conduction
2. Convection
3. Radiation

Conduction: Transmission of heat through a Sold body is called conduction.

Convection: Transmission of heat through Fluid is called convection.

Radiation: Transmission of heat through Electromagnetic waves is called  radiation.

*Sensible Heat: when a body is heated its temperature rises.

The increase in heat in a body is called Sensible Heat. Similarly when we remove heat from a body, the fall or decrease in heat is also called as Sensible Heat.
*It is defined as the amount of heat is removed or added to a substance without change in its state.
Units: kJ/kg-k
Mathematically it is given as 

Q_s=mC_p(ΔT)

where Q_s= sensible heat
           m= mass of substance
          C_{p= specific heat}
          ΔT= change in temperature
         

•  *It is denoted by h_f

*Latent Heat: The heat which brings changes in states in a substance with no change in temperature is known as Latent Heat.

Every pure substance has the ability to change in its state from Solid to liquid to gaseous state. 
Mathematically it is given as 

        Q_L=mL

Units: kJ/kg-k 

Q_L =Latent Heat
m= mass of substance
L= Latent heat of substance 
Note: Latent heat of fusion of ice is 336kJ/kg
               Latent heat of Condensation (Vapour-water) is 2258 kJ/kg

• *It is denoted by h_fg

Ex: Ice changes to water, water changes to vapor(gas) at same temperature. ie.,100^oC

  

*Specific Heat: It is defined as the amount of heat requited to raise 1 degree of temperature to a mass of a substance.

It is denoted by C. Unit of specific heat is taken as KJ/kg

=>If  m kg of a substance of specific heat is required to raise temperature from initial temperature T₁ to final temperature T₂, then heat required is

Q=mC(T₂-T₁) kj

 

Note: Specific heat of ice is 1.94 kJ/kg
               Specific heat of Water is 4.18 kJ/kg