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Isothermal Process
What Is an Isothermal Process in
Physics?
by Andrew Zimmerman
Jones
The science of physics studies
objects and systems to measure their motions, temperatures, and other physical
characteristics.
It can be applied to anything
from single-celled organisms to mechanical systems to planets, stars, and
galaxies and the processes that govern them.
Within physics, thermodynamics is a branch that concentrates on changes of
energy (heat) in the properties of a system during any physical or chemical
reaction.
The "isothermal
process," which is thermodynamic process in which the temperature of a
system remains constant.
The transfer of heat into or out of the system
happens so slowly that thermal equilibrium is maintained.
"Thermal" is a term
that describes the heat of a system.
"Iso" means
"equal", so "isothermal" means "equal heat,"
which is what defines thermal equilibrium.
The Isothermal Process
In general, during an
isothermal process there is a change in internal energy, heat energy, and work,
even though the temperature remains the same.
Something in the system works
to maintain that equal temperature.
One simple ideal example is
the Carnot Cycle, which basically describes how a heat engine works by
supplying heat to a gas.
As a result, the gas expands
in a cylinder, and that pushes a piston to do some work.
The heat or gas has to then be
pushed out of the cylinder (or dumped) so that the next heat/expansion cycle
can take place. This is what happens inside a car engine, for example.
If this cycle is completely
efficient, the process is isothermal because the temperature is kept constant
while pressure changes.
To understand the basics of
the isothermal process, consider the action of gases in a system.
The internal energy of
an ideal gas depends solely on the temperature, so
the change in internal energy during an isothermal process for an ideal gas is also 0.
In such a system, all heat
added to a system (of gas) performs work to maintain the isothermal process, as
long as the pressure remains constant.
Essentially, when considering
an ideal gas, work done on the system to maintain the temperature means
that the volume of the gas must decrease as the pressure on the system
increases.
Isothermal Processes and States of Matter
Isothermal processes are many
and varied.
Evaporation of water into the
air is one, as is the boiling of water at a specific boiling point.
There are also many chemical
reactions that maintain thermal equilibrium, and in biology, the interactions
of a cell with its surrounding cells (or other matter) are said to be an
isothermal process.
Evaporation, melting, and
boiling, are also "phase changes." That is, they are changes to water
(or other fluids or gases) that take place at constant temperature and
pressure.
Charting an Isothermal Process
In physics, charting such
reactions and processes is done using diagrams (graphs).
In a phase
diagram, an isothermal process is charted by following a vertical
line (or plane, in a 3D phase diagram) along a constant temperature. The
pressure and volume can change in order to maintain the temperature of the
system.
As they do change, it is
possible for a substance to change its state
of matter even while its temperature remains constant.
Thus, the evaporation of water
as it boils means that the temperature stays the same as the system changes
pressure and volume. This is then charted with the temperature staying constant
along the diagram.
What it all Means
When scientists study
isothermal processes in systems, they are really examining heat and energy and
the connection between them and the mechanical energy it takes to change or
maintain the temperature of a system.
Such understanding helps
biologists study how living beings regulate their temperatures.
It also comes into play in
engineering, space science, planetary science, geology, and many other branches
of science.
Thermodynamic power cycles
(and thus isothermal processes) are the basic idea behind heat engines.
Humans use these devices to
power electrical generating plants and, as mentioned above, cars, trucks,
planes, and other vehicles.
In addition, such systems
exist on rockets and spacecraft.
Engineers apply principles of
thermal management (in other words, temperature management) to increase the
efficiency of these systems and processes.
Edited and updated by Carolyn Collins
Petersen.
Andrew
Zimmerman Jones
Academic
researcher, educator, and writer with 23 years of experience in
physical sciences
Works
at Indiana Department of Education as senior assessment specialist in
mathematics
Co-author
of String Theory For Dummies
Member
of the National Association of Science Writers
Experience
Andrew
Zimmerman Jones is a former writer for ThoughtCo who contributed nearly 200
articles for more than 10 years. His topics ranged from the definition
of energy to vector mathematics. Andrew is a dedicated educator;
and he uses his background in the physical sciences, educational
assessment, writing, and communications to advance that mission.
Andrew
is co-author of String Theory For Dummies, which discusses the basic
concepts of this controversial approach. String theory tries
to explain certain phenomena that are not currently explainable under the
standard quantum physics model.
Since
2018, Andrew has worked at the Indiana Department of Education as a senior
assessment specialist in mathematics; prior to which he served as a senior
assessment editor at CTB/McGraw Hill for 10 years. In addition, Andrew was a
researcher at Indiana University's Cyclotron Facility. He is a member
of the National Association of Science Writers.
Education
Andrew
Zimmerman Jones has a Master of Science (M.S.) in Mathematics Education
from Indiana University–Purdue, Indianapolis, Ind.; and a Bachelor of Arts
(B.A.) in Physics from Wabash College, Crawfordsville, Ind.
Awards
and Publications
String Theory For Dummies (Wiley–For Dummies Series,
2009)
Graduated magna
cum laude (Wabash College, 1999)
Harold
Q. Fuller Prize in Physics (Wabash College, 1998)
ThoughtCo
and Dotdash
ThoughtCo is a premier
reference site focusing on expert-created education content. We are one of the
top-10 information sites in the world as rated by comScore, a leading Internet
measurement company. Every month, more than 13 million readers seek answers to
their questions on ThoughtCo.
For
more than 20 years, Dotdash brands have been helping people find answers,
solve problems, and get inspired. We are one of the top-20 largest content
publishers on the Internet according to comScore, and reach more than 30% of
the U.S. population monthly. Our brands collectively have won more than 20
industry awards in the last year alone, and recently Dotdash was named
Publisher of the Year by Digiday, a leading industry publication.
Carolyn
Collins Petersen
Author/co-author
of seven books on astronomy and planetary science, including Astronomy
101 and Space Exploration: Past, Present, Future
CEO of
Loch Ness Productions, a production company specializing in educational
materials for planetariums and science centers
Member
of the American Astronomical Society and International Planetarium Society
Experience
Carolyn
Collins Petersen is a science writer, producer, and former research astronomer.
She is the CEO of Loch Ness Productions, a production company specializing
educational documentary shows for planetariums and science centers. She has
published 7 books on astronomy and planetary science, including Astronomy
101, Space Exploration: Past, Present, Future, and Hubble Vision.
In
addition to her own books and articles on astronomy, Carolyn has written
exhibition texts for the Griffith Observatory in Los Angeles, the NASA/Jet
Propulsion Laboratory in Pasadena, and the California Academy of Sciences in
San Francisco.
Previously,
Carolyn worked on a Hubble Space Telescope instrument team and served as an
editor for Sky Publishing, which publishes Sky &
Telescope and Skywatch. Carolyn has written more than 40
documentaries and several webcasts on space science, and she regularly gives
public presentations and lectures on topics in astronomy.
Education
Carolyn
earned a master's degree from the University of Colorado – Boulder, where she
studied astronomy, astrophysics, and science communication. She also received
her B.S. from the University of Colorado.
Publications
Space Exploration: Past, Present,
Future, 2017, Amberley Books
Astronomy 101: From the Sun and Moon to Wormholes and Warp Drive, Key Theories,
Discoveries, and Facts about the Universe, 2013, Adams Media
Visions
of the Cosmos (with J.C. Brandt), 2005, Cambridge University Press
Hubble
Vision (with J.C. Brandt), 2003, Cambridge University Press (two
editions)
The
New Solar System (editor, with K. Beatty and A.C. Chaikin), 1999,
Cambridge University Press and Sky Publishing
Jupiter! 1989,
Facts on File.
ThoughtCo
and Dotdash
ThoughtCo is a premier
reference site focusing on expert-created education content. We are one of the
top-10 information sites in the world as rated by comScore, a leading Internet
measurement company. Every month, more than 13 million readers seek answers to
their questions on ThoughtCo.
For
more than 20 years, Dotdash brands have been helping people find answers,
solve problems, and get inspired. We are one of the top-20 largest content
publishers on the Internet according to comScore, and reach more than 30% of
the U.S. population monthly. Our brands collectively have won more than 20
industry awards in the last year alone, and recently Dotdash was named
Publisher of the Year by Digiday, a leading industry publication.
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