❖ Thermodynamics :- Branch of chemistry that explain the relation b/w heat and motion that means change
of heat during various process .
❖ System :- Specfic part of universe that undergo some observation (it has no boundary surface) at can
observe with change of temperature, pressure and volume.
❖ Surrounding :- Rest part of universe except system.
Relation b/w system and surrounding :- Both only exchange mass (matter) and energy with each other.
❖ Type’s of system :- Three types :-
1. Open system: - It can exchange both mass as well as energy with surrounding. e.g. Water heating in open
container, pressure cooker etc.
2. Closed system :- Only exchange energy not matter with surrounding. e.g. Water heating in closed
container.
3. Isolated system :- Neither exchange mass or energy. e.g. Thermo flask etc.
❖ NOTE :-
1. Microscopic System :- System have negligible mass. e.g. drop of water.
2. Universe :- System + Surrounding
❖ State of system :- Physical phase or state at which system is present in STP (general condition) called
state of system.
e.g. H2O(l), CO2(g), Iron(s) (Fe).
❖ State variable :- Physical quantity that change the state of system with changing its self. e.g.
Temperature.
❖ State Function :- Those property of system that depends upon initial and final state of system, it do not
depends upon the path by which system reach final state called state function. e.g. Internal energy (U),
enthalpy (H), entropy (s) etc.
❖ Microscopic property of system :- Property that represent by negligible mass or matter or small quantity
of constituent particle present in system called microscopic property of system.
e.g. charge,di-electric constant,di-pole moment.
❖ Macroscopic property :- That depend upon large quantity of matter. e.g. mass, volume, density,
temperature etc.
❖ It is two types :-
1. Intensive property :- Those property of system that do not depend upon the constituent particle or matter
present in system called intensive property. e.g. boiling point, melting point, freezing point, density,
refractive index etc.
2. Extensive property :- It depends upon constituent particle or matter (mass) of system called extensive
property. e.g. Internal energy, enthalpy, entropy (All thermodynamic property)
❖ Thermodynamic equilibrium :- Those process by which physical quantity of system remain same with
passing of time called thermodynamic equilibrium. (The quantities are temperature, internal energy etc)
❖ Thermodynamic process :- Process by which system change one physical state to other under some
condition of physical quantity called thermodynamic process.
It is following type:-
1. Iso-Thermal process :- Those process in which system can change one state to other but during the
process temperature of system remain constant.
For Iso-Thermal process,
∆T = T2 – T1 (Change in T = 0)
2. Adiabatic process :- During process heat of system remain constant.
i.e. ∆q = dq = 0 (q is heat)
3. Iso-choric process :- during process volume of system remain constant.
i.e. dv = ∆v = 0
4. Iso-basic process :- During the process pressure remain constant.
i.e. dp = ∆ P = 0
5. Reversible process :- Those process in which system can change into no. of state or infinite state with
existing equilibrium when condition is reverse it come back to their enitial state such process is known as
reversible process.For reversible process all property must be zero.
i.e. ∆U = 0, ∆ H = 0 etc.
6. Irreversible process :- Those process in which system can change into no. of state slowly without
existing equilibrium therefore, it cannot reverse back to their initial state, by reverse the condition such
process is known as irreversible process.
e.g. C + O2 CO2
❖ Law of Thermodynamics :- During the thermodynamic process there are certain rule that obey by
system called law of thermodynamic.
There are three law of thermodynamic
(a) 1st law of thermodynamics.
(b) 2nd law of thermodynamics.
(c) 3rd law of thermodynamics.
But there is one basic rule. i.e. 0th law of thermal equilibrium.
❖ 0th law of thermodynamics :- This law state that when three substance (A,B & C) are placed together in such a way that two substance ( A & B) are thermal equilibrium with 3rd (c) then both substance are also
thermal equilibrium with each other.
i.e. A C ……………. (i)
B C ………. (ii)
From equ (i) & (ii)
A B
A B
C
❖ Application :-
1. In proceed of thermodynamics process.
2. In change of physical state of system.
3. In cooking food.
4. Increase or decrease of temperature.
NOTE :- This law state heat always flow from high temperature to low temperature till temp. of both system
become equal.
❖ Internal energy ( U or E ) :- It is the total different type of energy that stored in a system at given
condition, such stored energy is called internal energy of system.
i.e. U = UK.E + UP.E + UHeat + Umass
……………………………
❖ Internal energy change (∆U) :- It is the difference of internal energy of system from final state to initial
state, Known as internal energy change.
Internal energy change (∆U) = U2 – U1 = Uf – Ui
Where , U2 – final internal energy. U1 – Initial internal energy.
❖ Property of ‘∆U’ :-
1. It is a thermodynamic process.
2. It is a state function.
3. It is an extensive property. (it depends upon mass or quantity)
4. for isolated system, isothermal process & reversible process, it is constant.
i.e ∆U = 0
5. It is a state variable.
6. If ∆U = +ve energy obsorb by system.
7. If ∆U = -ve , energy released by system.
8. Unit of ∆U, S.I unit = J C.G.S unit = erg 1J = 107
erg.
9. Process by which internal energy of system can be change :-
It can occur by three way :-
(i) By mass (ii) By heat (iii) By work done
(i) By mass :- Mass is form of energy so it directly perform to change internal energy.
(ii) By heat :- Heat is a form of energy that directly change the internal energy of system by tranferring one
system to another. (q)
Unit of heat (q) , S.I unit = J C.G.S unit = erg
Calorie = 4.184 Joule, 1 Joule = 0.2390 calories
Sign of ‘q’
(a) Heat absoerb by system , q = +ve
(b) Heat absoerb by system , q = - Ve
(c) q = 0 , for adiabatic process.
(iii) By Work done :- Work is said to be done if we applied a force in the system & that can displace to the
direction of force.
W = F X d , where F = applied force , d = displacement
Unit of ‘W’ :-
S.I unit = J or Nm
For any doubt or mistakes please kindly comment
