Plasma The 4th State Of Matter
Plasma Definition in Chemistry and Physics
What You Need to Know About the 4th State of Matter
Plasma lamps use radio frequency electricity to excite a gas
into the plasma state.
By Anne Marie Helmenstine, Ph.D.
PLASMA DEFINITION
Plasma
is a state of matter where the gas phase is energized until atomic
electrons are no longer associated with any particular atomic nucleus.
Plasmas are made up of
positively charged ions and unbound electrons.
Plasma may be produced by
either heating a gas until it ionized or by subjecting it to a strong
electromagnetic field.
The term plasma comes from a
Greek word that means jelly or moldable material.
The
word was introduced in the 1920s by chemist Irving Langmuir.
Plasma is considered one of
the four fundamental states of matter, along with solids, liquids, and gases.
While the other three states
of matter are commonly encountered in daily life, plasma is relatively rare.
EXAMPLES
OF PLASMA
The
plasma ball toy is a typical example of plasma and how it behaves.
Plasma is also found in neon
lights, plasma displays, arc welding torches, and Tesla coils.
Natural examples of plasma
include lightning the aurora, the ionosphere, St. Elmo's fire, and electrical
sparks.
While not often seen on
Earth, plasma is the most abundant form of matter in the universe (excluding
perhaps dark matter).
The stars, interior of the
Sun, solar wind, and solar corona consist of fully ionized plasma.
The interstellar medium and
intergalactic medium also contain plasma.
PROPERTIES
OF PLASMA
In a
sense, plasma is like a gas in that it assumes the shape and volume of its
container.
However,
plasma isn't as free as gas because its particles are electrically charged.
Opposite
charges attract each other, often causing plasma to maintain a general shape or
flow.
The
charged particles also mean plasma may be shaped or contained by electrical and
magnetic fields. Plasma is generally at a much lower pressure than a gas.
TYPES OF
PLASMA
Plasma
is the result of ionization of atoms.
Because it's possible for
either all or a portion of atoms to be ionized, there are different degrees of
ionization.
The level of ionization is
mainly controlled by temperature, where increasing the temperature increases
the degree of ionization.
Matter in which only 1% of
the particles are ionized can show characteristics of plasma, yet not be plasma.
Plasma may be categorized as
"hot" or "completely ionized" if nearly all the particles
are ionized, or "cold" or "incompletely ionized" if a small
fraction of molecules are ionized.
Note the temperature of cold
plasma may still be incredibly hot (thousands of degrees Celsius)!
Another way to categorize
plasma is as thermal or nonthermal.
In thermal plasma, the
electrons and heavier particles are in thermal equilibrium or at the same
temperature.
In nonthermal plasma, the
electrons are at a much higher temperature than the ions and neutral particles
(which may be at room temperature).
DISCOVERY
OF PLASMA
The
first scientific description of plasma was made by Sir William Crookes in 1879,
in reference to what he called "radiant matter" in a Crookes cathode
ray tube.
British physicist Sir J.J. Thomson's
experiments with a cathode ray tube led him to propose an atomic model in
which atoms consisted of positively (protons) and negatively charged
subatomic particles.
In 1928, Langmuir gave a name to the form of matter.
Anne Marie Helmenstine, Ph.D.
Anne
Helmenstine, Ph.D., is an author and consultant with a broad scientific and
medical background.
EXPERIENCE
Anne
has taught chemistry, biology, and physics at the high school, college, and
graduate level. In her doctoral work, Anne developed ultra-sensitive chemical
detection and medical diagnostic tests. She has worked abstracting/indexing
diverse scientific literature for the Department of Energy. She presently works
as a freelance writer and scientific consultant. She enjoys adapting lab-based
science projects so that they can be performed safely at home.
EDUCATION
Dr.
Helmenstine has bachelor of arts degrees in physics and mathematics with a
minor in chemistry from Hastings College in Nebraska and a doctorate of
philosophy in biomedical sciences from the University of Tennessee at
Knoxville.
ANNE MARIE HELMENSTINE, PH.D.
Chemistry
is part of everyone's life, from cooking and cleaning to the latest computer
chip technology and vaccine development. It doesn't have to be intimidating and
it doesn't have to be hard to understand.
You
can read more about Anne's current and past work on her Google Profile: Anne Helmenstine.
Find Anne's printable periodic tables and science projects at Science
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