Fundamentals of thermodynamics, System and Surroundings

System : A specified part of the (universe) which is under experimental verification.
Surrounding : Other than system is called surroundings
Boundary : Which divides system and surroundings.

Types of system :

Open system : Both energy and matter can be exchanged.
Closed system : Only energy can be exchanged it is sealed but not insulated.

Isolated system : Either matter or energy can't be exchanged here it is sealed and isolated, the boundary is adiabatic wall
Homogeneous system : Having only one physical surface
Heterogeneous system : Having more than one physical surface.

Thermodynamic process :

Isothermal process :
Takes place at constant temperature T
ΔPH = 0
It takes place in closed system.

Adiabatic process :
In which neither energy nor matter exchanged between system and surroundings.
It takes place in isolated system.
Temperature varies (i.e ↓ or ↑)
'Q' remains constant

Isobaric process : ΔP = 0
Takes place at constant pressure
Takes place when a freely movable piston is used
volume of system varies.

Isochoric process : ΔV = 0
Takes place at constant volume
occurs when piston fixed, pressure varies.

Cyclic process :
It proceeds through no.of intermediate stages and finally reaches to the initial state. ΔE = 0

A → B → Isobaric
B → C → Isochoric
C → D → Isobaric
A → D → Isochoric

Reversible process :
Proceeds through no. of infinitely small steps and very slow and in each stage it is in equilibrium
It is an ideal process
Practically not possible
Work done is maximum in reversible process.

Irreversible process :
→ which takes place in single step.
→ work done is not maximum.