This document provides an introduction to thermodynamics. It defines thermodynamics as the science of energy transfer and its effect on physical properties. Thermodynamics studies systems, surroundings, properties, processes, and equilibrium from a macroscopic viewpoint. The document outlines concepts such as intensive and extensive properties, homogeneous and heterogeneous systems, quasi-static processes, and the zeroth law of thermodynamics. It provides examples to illustrate these fundamental thermodynamics concepts.

1. Introduction to Thermodynamics
-ppt-1
Engg Thermodynamics-ME2102
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Presented by,
Lalitha P
Asst. Professor
Mechanical Engg.
RGUKT Basar

2. Introduction
• Thermodynamics is the science of energy transfer and its effect
on the physical properties of substances.
• Or, TD is defined as a fundamental science that describes the
basic laws in relation to different physical processes which
involve transfer or transformation of energy and the
relationship among the different physical properties of
substances which are affected by such processes.
• The word ‘thermodynamics’ is derived from Greek words
“therme” (means heat) and “dynamics” (means force).
• It is one of the fundamental subject to define the laws of natural
processes.
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3. • There are two views in the study of TD such as macroscopic and
microscopic point of views.
• In this study the macroscopic behaviour of a quantity of matter
will be analysed.
Macroscopic/classic view Microscopic/statistical view
Study on a certain quantity of matter
without consideration of the events
occurring at molecular levels.
The properties of matter are studied at
molecular levels.
Macroscopic thermodynamics is only
concerned with the effects of the action
of many molecules, and these effects can
be perceived by human senses.
If it is a gas you are analyzing, each
molecule at a given instant has a certain
position, velocity, and energy, and for
each molecules these change very
frequently as a result of collisions. The
behaviour of the gas is described by
summing up the behavior of each
molecule. Such a study is made in
microscopic thermodynamics.
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4. Thermodynamic system, surrounding and universe
• System is a quantity of matter or a region in space upon which
attention is concentrated in the analysis of a problem.
• Everything external to the system is called the surrounding or
environment.
• The system and surrounding are separated by the system
boundary. It may be fixed (rigid) or moving (flexible).
• The system and its surroundings together comprise an universe.
• Types of systems: open system, closed system and isolated
system.
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6. Homogeneous and Heterogeneous systems
• A quantity of matter is homogenous throughout in chemical
composition and physical structure is called a phase.
• Every substance can exist in any one of the three phases, viz.
solid, liquid and gas.
• A system consisting of a single phase is called a homogeneous
system.
• While a system consisting a more then one phase is known as
a heterogeneous system.
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7. Thermodynamic properties, processes and cycles
• Each system has certain characteristics by which its physical
condition may be described, such characteristics are called as
properties.
• Eg: pressure, volume, temperature, etc.
• These are all macroscopic in nature.
• System is said to be in a definite state when all the properties
have definite values.
• Properties are the coordinates to describe the state of the
system.
• Any operation in which one or more properties of a system
changes is called change of state.
• Succession of states passed through during a change of state is
called the path of the change of state.
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8. • When the path is completely specified, the change in state is
called a process.
• A thermodynamic cycle is defined as a series of change in state
such that the final state is identical with the initial state.
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1-is the initial and final state
of a cyclic process 1-2-1
a-b: a process

9. Classification of Properties:
Intensive properties
• Independent of the mass of the
system
• Or, The properties of matter that do
not depend on the size or quantity
of matter in any way are referred to
as an intensive property of matter.
• Eg: pressure, temperature, density,
etc.
• Any extensive properties per unit
mass is also called as intensive
properties or specific extensive
properties.
• Eg: specific volume (=
volume/mass), specific energy,e tc.
extensive properties
• dependent of the mass of the
system
• If the value of the property of a
system is equal to the sum of the
values for the parts of the system
then such a property is called
extensive property.
• Eg: mass, volume, energy,
enthalpy, entropy, etc.
• If mass of the substance is
increased, then the extensive
properties will also be increased.
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10. Thermodynamic Equilibrium
• If a system is isolated from the surroundings then there will be
no macroscopic properties changes will be registered, so the
system is said to be in thermodynamic equilibrium.
• An isolated system always reaches in course of time a state of
thermodynamic equilibrium and can never depart from it
spontaneously.
• i.e., no spontaneous change in macroscopic properties in the
system is in equilibrium state.
• TD studies mainly carried in these equilibrium states.
• A system will be in a thermodynamic equilibrium state is it
satisfies the conditions of following types of equilibrium, such as
i. mechanical equilibrium
• ii. Chemical equilibrium
• Iii. Thermal equilibrium
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Mechanical Equilibrium
When the bodies A and B are
at the same position.
If a body is already at mechanical and chemical
equilibrium conditions, then only it attains its
thermal equilibrium condition.

12. Quasi-static process
• A process, in which all the states are in equilibrium in a state is
called quasi-static process or quasi-equilibrium process.
(Quasi means ‘almost’ )
• Characteristic feature of a quasi-static process is infinite
slowness.
• Quasi-static process is made by the path in which succession
of equilibrium states are joined together.
• So it is also a reversible process.
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15. Zeroth law of thermodynamics
• When a body ‘A’ is in thermal equilibrium with another body
‘b’, and also separately in thermal equilibrium with a body ‘C’,
then body ‘B’ and ‘C’ will also be in thermal equilibrium with
each other.
• “Systems that are in thermal equilibrium exist at the same
temperature”.
• The law is based on temperature measurement.
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16. • Property that changes with temperature are referred as
thermometric property eg; pressure, volume.
• In order to obtain a quantitative measure of the temperature
of the bodies, a reference body will be used. That reference
body is known as thermometer.
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Pic courtesy : NASA