CHAPTER-1 BASICS OF THERMODYNAMICS
Thermodynamics is the branch of science which deals with energy interaction between one body to
another body and the effect of the energy transfer on them.
A system is defined as a quantity of matter (control mass) or a region (control volume) in space
chosen for study.
Everything external to the system is called the surroundings or the environment.
• A real or imaginary surface that separates the system from its surroundings
• Mathematically, the boundary has zero thickness, and thus it can neither contain any mass nor
occupy any volume in space.
• The boundary may be either fixed or moving.
• A system and its surroundings together comprise a universe.
• Universe consists of everything, so everything happening whether energy transfer or
transformation or losses remain inside the universe.
TYPES OF SYSTEM
A. Depending upon the mass and energy interaction.
a. Open System
• when there is mass as well as energy can transfer across the boundary.
• Example - air compressor, boiler, pump, IC engine with valve open etc.
b. Closed system
• if its mass remains fixed but there may be energy transfer into or out of the system
• Example – a certain quantity of fluid in a completely enclosed cylinder, Tea in kettle etc.
c. Isolated system
• when there is no mass and energy interaction between the system and the surroundings.
• Example – thermo-flask, Universe (since all energy interaction taking place between
systems and surrounding which is the part of the universe)
B. Depending upon the Chemical Composition
a. Homogeneous System
• A quantity of matter homogeneously distributed throughout the system with respect to its
chemical composition and physical structure are called homogenous system.
• A system consisting of a single-phase is called a homogeneous system.
b. Heterogeneous System
• A system consisting of more than one phase is known as a heterogeneous system.
• Heterogenous system is the combination of two or more homogeneous system.
• In the macroscopic approach, a certain quantity of matter is considered, without molecular level
being taken into account.
• It is also known as the classical approach. All the properties will be the average of the properties of
each molecule passing through that space.
• From the microscopic point of view, the matter is composed of numbers of molecules and study is
made on a molecular level.
• It is also known as the statistical approach. In this approach, we sit on a particular molecule and
whatever changes occur is recorded and an average of this will be our required properties.
CONCEPT OF CONTINUUM
• The concept of the continuum is an idealization of the continuous description of matter where the
properties of the matter are considered as continuous functions of space i.e. the space between
the molecules (mean free path) is almost zero or very small as compared to the size of the system.
• At very low pressure (i.e. space outside earth atmosphere) gas is studied by Gas rarefied theory
in which a microscopic approach is used.
• Example: Density is calculated assuming continuum concept, so we assumed the same uniform density
all over the material.
• The properties which dependent on mass is known as ext
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