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What is difference bitween enthalpy and internal energy?

What is difference bitween enthalpy and internal energy?
 

Grade:12

2 Answers

Arun
25750 Points
5 years ago
  • We know that there are two types of system in thermodynamics first is close system and another is open system.
  • Internal energy is one type of property related to temperature,potential energy , and kinetic energy means it is main characteristic of the substance...
  • Now in close system there is not any flow of mass through system boundary but in case of open system there is a permission of mass flow or exchange....
  • For the flow of mass the mass should have some energy
  • In fluid mechanics we know that the energy of fluid can be written in terms of pressure and the volume.
  • So that in open system there are two types of energy in system (in open system 'control volume' term is used) one is internal energy (discussed above) and another is energy required for exchange of mass through the system....
  • So combination of both the property is called 'enthalpy'...

Note: (sometimes there is also an enthalpy in close system like in which there is change in volume of system but it is only a combined form of change in internal energy and work done by system. By the way real origin of enthalpy is open system)
 
  • So in one sentence enthalpy is combination of system's energy + energy required for mass exchange or due to mass exchange
REENU SIVADARSHINI.M
118 Points
5 years ago
ENTHALPY :
 It is defined as the sum of the internal energy and the product of pressure and volume
        H=U+PV
INTERNAL ENERGY :
 It is equal to the energy possessed by all the constituent in it like atoms , ions and molecule
                                          or
The total energy of all the molecule of the system is internal energy

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