Thermodynamics is the science of energy transfer and its effect on physical properties. It is concerned with macroscopic properties that can be observed by the human senses, such as pressure, temperature and volume. A thermodynamic system is defined as a region in space that is separated from its surroundings by a boundary. Systems can be open, closed, or isolated depending on whether mass and/or energy are allowed to transfer across the boundary. Thermodynamic properties describe the state of the system, and a change in state through a succession of equilibrium states is called a process. Thermodynamics can predict equilibrium states and the natural direction of change in non-equilibrium systems.

1. Thermodynamics
S.Gunabalan
Associate Professor
Mechanical Engineering Department
Bharathiyar College of Engineering & Technology
Karaikal - 609 609.
e-Mail : gunabalans@yahoo.com

2. Thermodynamics
Thermodynamics is the science of energy transfer and
its effect on the physical properties of substances.
Thermo = HEAT (or Energy)
Dynamics: Movement
The Temperature - a quantity which indicates how hot
or cold the body is
Temperature is indicator of direction for heat flow.

3. Thermodynamics
Thermodynamics is the science of energy transfer and
its effect on the physical properties of substances.
1. Macroscopic thermodynamics is only
concerned with the effects of the action of many
molecules, and these effects can be perceived by
human senses.
2. The behaviour of the gas is described by
summing up the behaviour of each molecule. Such a
study is made in microscopic or statistical
thermodynamics.

4. Thermodynamic System
• Thermodynamic system is defined as a region
in space upon which attention is concentrated
in the analysis of a problem.
surroundings : Everything external to the system
is called the surroundings or the environment.
boundary : The system is separated from the surroundings
by the system boundary

5. Thermodynamic System

6. Thermodynamic System
Open system
http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/A_System_And_Its_Surroundings
A open system is defined when a fixed volume is under
study. There can be mass transfers as well as energy
transfers across the boundary.

7. Thermodynamic System
• Truly isolated systems cannot exist in nature,
• The only possibility is the universe itself,
• So its is a hypothetical concepts
http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/A_System_And_Its_Surroundings
isolated systems

8. Thermodynamic System
http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/A_System_And_Its_Surroundings
Closed systems
• A closed system is a system that exchanges only energy with its
surroundings, not matter.
• Matter can no longer transfer because the lid prevents matter from
entering the pan and leaving the pan. Still, the pan allows energy transfer.
A closed system always contains the same matter. There can be no
mass transfers across the boundary. There may be energy transfer
across the boundary.

9. Thermodynamic System
http://nptel.iitm.ac.in/courses/Webcourse-
contents/IIT%20Kharagpur/Ref%20and%20Air%20Cond/R&AC%20Web%20files/R&AC%20Lecture%204/hyperlinks/systems.htm
Example
the contents of a pressure cooker on a stove with its lid
tightly closed and the whistle in position, is a closed
system as no mass can enter or leave the pressure
cooker, but heat can be transferred to it.
When the whistle of the pressure cooker blows, then it
becomes an open system as steam leaves the cooker.
A perfectly insulated, rigid and closed vessel is an
example of an isolated system as neither mass nor energy
can enter or leave the system.

10. Properties
• Thermodynamic properties are observable or
measurable properties of the system(pressure,
temperature, volume)
– Classification of properties
1. Intensive properties (Independent of mas)
Properties have same value in any part of the system and it
is independent of mas (pressure, temperature)
2. Extensive properties (mas dependent)
depends on mass of the system and de not maintain same
value across the system (mass, volume, enthalpy, energy)

11. State
The specific condition of the system is called
State of the system.
the properties are used to describe the
state of the system.
Path : The succession of states passed through
during a change of state is called the path
Process: the path is completely specified, the
change of state is called a process

12. Thermodynamic Equilibrium
• when no change in any macroscopic property
then the system is in equilibrium

13. Applications of thermodynamics
•To predict the equilibrium state of a reactive
mixture as well as the natural direction of
change in a system not at equilibrium
•thermodynamics can’t predict how long it
takes for equilibrium to be reached

14. Reference
• Nag, P. K. 2002. Basic and applied thermodynamics. Tata
McGraw-Hill, New Delhi.
• http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodyn
amics/A_System_And_Its_Surroundings
• http://nptel.iitm.ac.in/courses/Webcourse-
contents/IIT%20Kharagpur/Ref%20and%20Air%20Cond/R&AC
%20Web%20files/R&AC%20Lecture%204/hyperlinks/systems.
htm ( date 25-june-2013)