Thermodynamics,
The word
thermo means heat and dynamics means changes, thermodynamics is the physics of
how thermal energy is change into work and work is the product of force and displacement.
Thermodynamics deal with how heat energy can change into mechanical, electrical
and chemical energy. In simple terms thermodynamics is the physics of how heat does
work in a system. Thermodynamics deal with macroscopic property of a system
like temperature, pressure, volume etc.
It deals with
the relationships between heat and other forms of energy, according to Lord Kelvin
thermodynamics is defined as the subject
of the relation of heat to forces acting between contiguous parts of bodies and
relation of heat to electrical agency. In other word thermodynamics can be defined
the science concerned with relation between heat and mechanical energy or work,
and conversion of one form into another.
thermodynamic deals with work and for a work
to be done, there must be a force and change of distance, distortion or
displacementf, without change in displacement workdone is zero, work done is give by force x displacement,
the force can take several forms depending on the medium or from of energy that
do the force, likewise the displacement can take several form depending on the
medium/object that do the work. In elastic wire the force is tension and the displacement
is extension, in gases the force is pressure and the displacement volume, in liquid
the force is surface tension and the displacement is length, and electric cell
the force is potential difference and the displacement is charge, in magnetic system
the force represent magnetic induction and the displacement represent magnetization
etc. In all the above the displacements must change respectively before a work
is said to be done otherwise workdone is zero. The work can be internal or
external,
·
Internal
work when the work is done by one part of a system on another.
·
External
work if the works applies to the system as a whole.
In
thermodynamics there must be system, system
is any part of universe that have being chosen for studying the changes that
take place within it in response to varying condition, a system is any entity
that have chosen for study. There are three types of system, namely; any system
that exchanges neither matter nor energy with its surrounding is called an
isolated system, any system that exchanges only energy with its surroundings is
called closed open system, and any system that exchanges only matter with its
surrounding is called open system while any part of the universe outside system
is called surroundings.
There are
two main thermodynamic properties, the intensive and extensive, a function is
said to be intensive when it does not depends on the size of the system. Eg.
temperature ,melting point, boiling point, refractive index, density ,intensive as a
physical property , it value does not depend on the amount of material
being measured. Property like temperature does not depend on the amount of
material being measured, example the temperature a part of a system is same as
that of the rest, the density of part of a homogenous system is same as that of
all of it,
While
extensive properties depend on the size or amount of the system, example are
mass, volume etc, the volume of a portion of a system is far less than the
volume of an entire system, the mass of a 1/3rd of a system is far
less than mass of the whole system, the latent heat of a portion of a system is
far less than that of part of it. Mass, volume, latent heat is therefore
extensive properties because their volume is depending on the size or amount of
the system.
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