Macroscopic properties  


 The properties which arise from the behavior of matter are called macroscopic properties.                                                                                                    (a) Extensive properties. The thermodynamic properties which depend upon the amount of the substances or substances present in the system are called extensive properties.                                             
Example: Mass, volume, heat capacity, internal energy, enthalpy, Gibb's free energy etc.               
(b) Intensive properties. The thermodynamic properties which depend only on the nature of the system and are independent of the amount of the substance present in the system are called intensive properties.
Example: Temperature, Pressure, density, viscosity, surface tension etc.
State of the system and state variables
 (a)State of the system. The condition of existence of a system when its macroscopic properties have a definite value is called the state of the system.
               with the change in   one macroscopic property, the state of the system changes
 (b)State variables. The measurable properties required to describe the state of the system are called state variables.
               Four common properties which are sufficient to define the state of the system are composition, pressure, volume, and temperatures.
State function
               It is the property of the system whose value depends only upon the initial and final state of the system and not upon the path by which the change has been achieved.
               Example: Internal energy, enthalpy, entropy, free energy, etc.

 Thermodynamics process
             (a)Isolated process: A process which takes place at constant temperature is called isothermal
process. Such a process can be carried by placing the system in a constant temperature bath.
             (b)Adiabatic process: A process in which no heat exchange takes place between the system and the surrounding is called adiabatic process. Such a process can be carried in a thermally insulated vessel.
             (c)Isobaric process: A process which takes place at constant pressure when the system is in equilibrium with the surrounding is called isobaric process. It is carried in a vessel fitted with the frictionless and weightless piston.
             (d)Isochoric process: A process which takes place at constant volume is called the isochoric process. Such a process can be carried in a bomb calorimeter.
Reversible process:
             A reversible process is one in which the change is carried out infinitesimally slowly so that the system and the surrounding remain always is an equilibrium
Or
       The process which has both forward and backward directions are known as the reversible process.
Irreversible Process:
            An irreversible process is one in which the change is carried out rapidly so that the system does not get any chance to attain equilibrium.
Or
       The process which has the only forward reaction and no backward direction is known as the irreversible process.

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