Thermodynamics ,TYPES OF SYSTEM,heat energy ,internal heat energy ,gibbs free energy

1. FUNDAMENTALS
OF
THERMODYNAMICS
Presented by –Rashm
MSc. 2 year 3sem
Session-2023-24

2. Thermodynamics
It is a branch of chemistry which deals with the study of energy changes
accompanying all types of physical and chemical processes. Father of
thermodynamics – Sadi Carnot
Some basic concepts
1.System – The part of the universe in which energy changes are studied is
called system.
2.Surrounding – The rest of the universe which surround the system is called
surrounding . The system and surrounding are separated by real /imaginary
boundary.
System +Surrounding =Universe

3. Types of system
1.Open system - A system which can exchange both energy and matter with the
surrounding is called an open system . Ex-evaporation of water from a beaker
represents an open system . Here vapours move into atmosphere.
2.Closed system - A system which can exchange only energy but not matter
with surrounding is called closed system . Ex- Boiling of water in a closed metallic
container.
3.Isolated system – A system which can neither exchange energy nor matter
with the surrounding is called isolated system
. Ex-Hot tea placed in a thermas flask.
4.Macroscopic system – A system
consists of large number of atoms ,
ions or molecules is called
macroscopic system .
Ex – Temperature , pressure ,
concentration.
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4. TYPES OF PROPERTIES
1.Extensive property – The properties which depend upon the amount of substance
present in the system are called extensive properties.
Ex – mass , volume , heat capacity , internal energy.
2.Intensive property – The properties which depend upon the
nature of substance present in the system are called intensive property .
Ex – pressure, temperature , density , viscosity .
STATE OF SYSTEM
1.State function – A property whose change in the value depends upon only initial and final
states of system and not on path followed by system.
Ex – internal energy (E) , enthalpy , entropy ,pressure , volume , temp.
2. Path function – properties which depend upon path followed by system is called path
function . Ex – work and heat.
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5. *HEAT (q)
Heat is a form of energy exchanged between the system and the surrounding at different temp.
A body at higher temp transfers heat energy to the body at lower temp.
Unit- SI unit is JOULE
C.G.S unit is ERG
Sign convention :
1)Heat absorbed by the system, +ve sign
2)Heat evolved by the system ,-ve sign
INTERNAL ENERGY (E)
It is the sum of different forms of energy associated with atoms and molecules such as
electronic energy (Ee) ,nuclear energy (En), chemical bond energy (Ec) ,kinetic energy (Ek)
and potential energy(Ep) .
Thus , E = Ee+ En+ Ec+ Ek+ Ep

6. *WORK (W)
Energy can also be exchanged between system and surrounding as work if
they are at different temperature . If pressure inside system is higher than
surrounding ,the system will expand in order to reduce the pressure and
then work is said to be done by the system . If pressure of surrounding is
higher than the system contracts and the work is said to be done on the
system.
If P is external pressure and V is change in volume then workdone =P
V
Unit : SI unit is JOULE
CGS unit is ERG
Sign convention:
1)Workdone by the system , -ve sign.
2)Workdone on the system , +ve sign.
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7. THERMODYNAMIC PROCESS
The process which brings about the changes in thermodynamic state of the
system is called thermodynamic process . Thermodynamic processes are as
follows:
1.Isothermal process-The process carried out at constant temp is called
isothermal process.
2.Isobaric process-The process carried out at constant pressure is called
isobaric process.
3.Isochoric process-The process carried out at constant volume is called
isochoric process.
4.Adiabatic process-The process in which no heat exchange takes place
between the system and the surrounding .
5.Cyclic process-The process which brings back the system to initial state
after series of changes is called cyclic process.

8. REVERSIBLE PROCESS
A process which is carried out so slowly that all changes occurring in a direct
process can be exactly reversed and system remains almost in equilibrium with
surrounding at every stage of process is called reversible process.
IRREVERSIBLE PROCESS
The process which is not carried out slowly so that different steps of direct
process cannot be reversed.
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9. LAWS OF THERMODYNAMICS
FIRST LAW
This law was given by RUDOLF CLAUSIS in 1850.It is also known law of
conservation of energy . This law states that energy can neither be created
nor be destroyed although it can be converted from one form to another. This
law holds good in chemical reaction also. Energy may be absorbed or evolved
in a chemical reaction but the total energy of reacting system and surrounding
remains constant i.e. the total energy of the universe remains constant.
Internal energy E1 and workdone on the system
E1+q+w
Internal energy in final state ,E2
E2=E1+q+w
E2-E1=q + w
E= q + w
This is the mathematical expression of 1st law of thermodynamics .This law
cannot state whether a rx is spontaneous or not .
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10. SECOND LAW OF THERMODYNAMICS
It states that a process can occur spontaneously only if the sum of entropies of
system and its surrounding increases or the universe tend towards the maximum
disorder.
ENTROPY
It is the measure of degree of randomness or disorder of a system .
S= Q/T
ENTHALPY
It is defined as the sum of internal energy and product of pressure and volume
i.e. total heat content of the system.
H= E+P V
H , Enthalpy change-It is equal to the heat evolved
or absorbed at constant pressure.
SIGN CONVENTION :
1) H is +ve for endothermic rxn

11. 1)EXOGONIC REACTION
When a rxn proceeds with release of free energy and G has –ve value ,the rxn is
said to be exogonic rxn.
ex- Glycolysis, ETC, oxidative phosphorylation
2)ENDOGONIC REACTION
In this rxn ,the system gains free energy and the value of G is +ve .
ex- Gluconeogenesis, Photosynthesis.
3)EXOTHERMIC REACTION
When a chemical rxn releases heat and the value of H is –ve ,is said to be
exothermic reaction .
4)ENDOTHERMIC REACTION
When a chemical rxn stores or gains heat is called endothermic rxn and value of H
is
+ve .
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12. GIBBS FREE ENERGY
It is proposed by J.W.Gibbs .It expresses the amount of energy capable of doing
work during a rxn at constant temperature and pressure.
G = H – TS or G= H – T S
Thus G of rxn is valuable criterion of whether that rxn can occur
Spontaneously.
1. G is –ve ,rxn occur spontaneously.
2. G is 0,system is at equilibrium.
3. G is +ve ,rxn cannot occur .
STANDARD FREE ENERGY
Change in gibbs free energy under standard conditions in free energy is called
standard free energy.

13. 1) When change in standard free energy is –ve , the product contains less free
energy then the reactant under standard conditions .The reaction will
proceed spontaneously .
2) When change in standard free energy is +ve ,the product of reaction contain
more free energy tan reactant , this reaction will tend to go in reverse
direction.
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14. HESS LAW
This law was given by G.H.HESS , a Russian chemist in 1840. This law
states that the total amount of heat evolved or absorbed in a chemical
reaction is the same ,no matter whether the reaction occurs in one step or
more than one steps.
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15. • Thermodynamics Examples in Daily
Life
• We came across various examples in our daily life which can be
explained using thermodynamic properties. Some of them are,
• Melting of Ice Cubes: Drinks with ice cubes become cooler
as the heat from the drink is absorbed. If we neglect to drink it, it
will eventually warm back up to room temperature by absorbing
heat from the environment. The first and second laws of
thermodynamics govern how all of this works.
• Sweating in a Crowded Room: In a crowded room,
everyone begins to sweat. By transmitting body heat to the
sweating, the body begins to cool down. Sweat evaporates,
heating the space. Again, this occurs as a result of the application
of the first and second laws of thermodynamics. Keep in mind that
heat is not lost but rather moved until equilibrium is reached with
the least amount of entropy.
• Flipping a Light Switch: Different kinds of power plants,
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16. REFERENCES
1.Biochemistry –Harper
2.Ncert 11/12
3.Fundamentals of thermodynamics-
Borgnakke.
Thank you have a nice day