Basic concepts and Thermodynamic Description of system,zeroth law of thermodynamics, first law of thermodynamics, internal energy

1. S.Y. B.Sc.
Thermodynamics and Kinetic Theory of
Gases
K.B.C. North
Maharashtra University

2. Dr. Mrs. Pritee M. Raotole
Basics of Thermodynamics 1

3. Stay Safe!!!!!

4. Basics of Thermodynamics
Introduction
Thermodynamic Description
of System,
Zeroth Law of
Thermodynamics
First Law of thermodynamics
Concept of Internal Energy,
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

5. Introduction
• Thermodynamics is a branch of Physics
which deals with the conversion of heat
into other forms of energy and vice versa.
• In thermodynamics, study of macroscopic
properties like pressure, volume,
temperature etc.
• These quantities are called as the
thermodynamic co-ordinates.
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

6. Introduction
• We mostly consider a finite quantity of
matter which we call as system
• e.g. A gas enclosed in a cylinder fitted
with a piston can be considered as a
system.
• Anything outside the system, which
exchanges energy with the system and
which affects the behavior of the system,
is called its surrounding or environment.
• The system & its surroundings are
together known as the universe.
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

7. Introduction
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8. Introduction
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

9. Thermodynamic Description of
system
• Let us say for example we are studying
the engine of the vehicle, in this case
engine is called as the system.
• Similarly, the other examples of system
can be complete refrigerator, air-
conditioner, washing machine, heat
exchanger, a utensil with hot water etc.
• Types of Thermodynamic Systems
• There are three mains types of system:
open system, closed system andDr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

10. Closed system
• The system in which the transfer of energy
takes place across its boundary with the
surrounding, but no transfer of mass takes
place is called as closed system.
• The closed system is fixed mass system. The
fluid like air or gas being compressed in the
piston and cylinder arrangement is an
example of the closed system.
• In this case the mass of the gas remains
constant but it can get heated or cooled.
• Another example is the water being heated
in the closed vessel, where water will getDr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

11. Open system
• The system in which the transfer of mass as
well as energy can take place across its
boundary is called as an open system.
• Our previous example of engine is an open
system. In this case we provide fuel to
engine The engine also emits heat which is
exchanged with the surroundings. thus
there is exchange of mass as well as energy.
• The other example of open system is boiling
water in an open vessel, where transfer of
heat as well as mass in the form of steamDr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

12. Isolated system
• The system in which neither the transfer of
mass nor that of energy takes place across
its boundary with the surroundings is called
as isolated system.
• For example if the piston and cylinder
arrangement in which the fluid like air or
gas is being compressed or expanded is
insulated it becomes isolated system.
• Here there will neither transfer of mass nor
that of energy. Similarly hot water, coffee or
tea kept in the thermos flask is closed
system.
• However, if we pour this fluid in a cup, itDr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

13. Open, Closed and Isolated
System
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

14. Types of Systems
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

15. ZEROTH LAW OF
THERMODYNAMICS
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

16. ZEROTH LAW OF
THERMODYNAMICS
• systems B and C are isolated from each
other by an adiabatic wall. Both systems (B
and C) are in contact simultaneously with a
third system A through a diathermic wall.
• Experiment shows that as time passes,
systems B and C will separately attain
thermal equilibrium with system A.
• Now if the adiabatic and diathermic walls
are interchanged, no further change in a
state of any of the three systems will occur.
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

17. ZEROTH LAW OF
THERMODYNAMICS
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18. Statement of ZEROTH LAW
• Zeroth law of thermodynamics. It states
that,
• “If two systems are separately in
thermal equilibrium with a third system
then they themselves are in thermal
equilibrium with each other”.
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

19. First Law of Thermodynamics
• The first law of Thermodynamics is a
version of the law of conversion of energy.
• It is adapted for thermodynamic, processes
distinguishing two kinds of transfer of energy,
as heat and as thermodynamic work, and
relating them to a function of a body's state,
called Internal energy.
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

20. Example of first law of
thermodynamics
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

21. First Law of Thermodynamics
• “Whenever mechanical work is converted
into heat or heat is converted into
mechanical work, there exists an exact
equivalence between the two.”
W = H, (if both are measured in same unit )
W = JH
(if work is measured in units of work and heat is
measured in calories).
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

22. First Law of Thermodynamics
• However practically the heat supplied to
a body may not be entirely converted
into work. part of it may be used to
change the internal energy of the body
and remaining part of it may be used in
performing external work.
• Let dQ be the quantity of heat absorbed
by a thermodynamic system, dU be the
increase in its internal energy and dW be
the external work performed by the
system Then
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

23. Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

24. Internal Energy
• When a piece of coal is burnt, we get heat and
light. The fact suggests that some amount of
energy is stored in a material.
• “The energy stored in a substance or
system is known as its internal energy”.
• “The total of all the possible kinds of
energy of a system is called its internal energy”.
• It is neither possible nor necessary to calculate
the absolute value of internal energy.
• However we can find or measure the change in
internal energy when a system changes from one
state to another state.
• It is denoted by ΔU.
• Internal energy depends only on present or
current state of the system and is independent of
the path by which the state was reached.Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

25. Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

26. Internal Energy
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,

27. Thank You
Dr. Mrs. Pritee M. Raotole, MGSM’s Arts Science and Commerce,