Property of a system

Property represents any observable chara-cteristics of the system.  Property of a system depends only on its state , irrespective of how that state was attained. 

Intensive property -: If a property of  a system does not depend upon it's mass , it is intensive property. For example,  pressure, temperature, density,  etc .

Extensive property -: when the property of any system is depend upon the mass it is called extensive property. For example enthalpy , volume, etc .

 

If a given quantity depend on two para-meters is connected such that these para-meters are connected by a line path , then the quantity is not a property . if an given quantity is an exact differential,  it is pro-perty ,otherwise no .

Free energy and free Enthalpy

Free energy -: Free energy ( or Helmholtz function) is defined as  f = u - Ts .

It is equal to the work during a constant- volume isothermal reversible nonflow process .

Free Enthalpy -: Free enthalpy ( or Gibbs function ) is defined as  g = h - Ts

Where , u = internal energy  h = enthalpy ,      T = temperature, s = entropy 

Gibbs function is of particular importance in processes where chemical changes occur. For reversible isothermal steady flow pro-cesses or for reversible constant- pressure isothermal nonflow processes , change in free energy is equal to net work .

Definitions

Macroscopic approach :-               macroscopic deals with certain quantity of matter  and its behaviour. 

Microscopic approach  :-                microscopic approach concerned with molecular and atomic behaviour of energy and matter.

Thermodynamic system :--Thethermodynamic system is a fixed quantity of matter, around which we can draw a boundary. The boundary may be moveable or fixed. 

There are 3 types of system -- 

1.  Closed system :-                                             In this system there is no interchange of matter between surrounding and system . In this system only energy can cross the boundaries and the boundary also can move or change its position .

2.Open system :-                                                     In this type of thermodynamic system matter and energy both can interchange from the system.

3. Isolated  system :- 

   In this type of thermodynamic system both matter and energy no one can cross the boundaries. Isolated system not influenced by the surrounding .