Thermodynamics equilibrium and properties of a system

Thermodynamics equilibrium 

A body is said to be in a thermodynamics equilibrium if it is in 

1. Thermal equilibrium: Equality of temperature 
2. Mechanical equilibrium: Equality of force and couples.
3. Chemical equilibrium: Equality of chemical potentials.

Properties of a system 

Properties are point functions and are exact or perfect differential. 

Properties are not path functions 

From the above graph 

A and B are the two paths between points 1 and 2.

Properties are of two types 

1. Extensive properties: These properties are dependent on mass. e.g. volume, energy, heat capacity, enthalpy. For example volume=(mass) / (density). Where volume is dependent on mass. Similarly energy unit is joule where Joule=(Kg*m^2)/sec where Kg is mass which plays an important role in value of energy.
2. Intensive properties: These properties are independent on mass. e.g. pressure, temperature, density, specific volume, specific heat, specific enthalpy. For example pressure is not dependent on mass. Same pressure can be obtained for different masses at different volumes. Temperature can be same for different masses. 

• Specific properties: specific properties are extensive properties per unit mass. Specific properties are intensive properties whose mass is cancelled.  For example specific volume= (volume) / (mass) where volume is denoted by capital 'V' and specific volume is denoted by small 'v'. And specific enthalpy=(enthalpy)/(mass) where enthalpy is denoted by 'H' and specific enthalpy is denoted 'h'. 

Point functions: Does not depend on path history (Temperature, pressure, volume). These properties are measured at a particular point of the system. 

Path functions : Depends on path history (work, heat). Because work is said to be done if it changes from one state to other state.