The Fourth State of Matter: Plasma
Presentation:
We talked about the 3 states of matter -- Solid, liquid and gas. Well, there is another state of matter
called Plasma.
Plasma is formed when matter is given a whole lot of energy. Just as it takes a lot of energy to change a
solid into a liquid, and even more energy to turn a liquid into a gas, it also takes an even greater amount
of energy to change matter into plasma. Just as different things melt at different temperatures, so also do
different things turn into plasma at different amounts of energy. However, it takes so much energy that
plasma is pretty rare and requires very special conditions.
Here are some examples of plasma:
Lightning: Lightning is a form of plasma. It is from static electricity in the clouds.
Have you ever pulled a sweater off in the winter and gotten a shock? Or rubbed a ballon in your hair and your hair sticks to it? That is static electricity. When thick, heavy
rain clouds move over the earth, it is like rubbing a thick sweater across your skin. It
causes energy to build up. It builds up so much that it has to be released. The energy
is so strong that it makes a crack in the air and the energy drains through the crack to
the ground as plasma. This is why lighting looks like a crack. It happens in an instant,
a flash of light When the plasma runs out, the crack slams shut so fast that it is faster
than the speed of sound itself. The sound of the air smacking back together is the
sound of thunder.
Neon signs: Neon signs are a more tame form of plasma. Neon has two electrodes and the energy flows from one end to the other as plasma contained in the glass. Plasma globes have one
electrode in the center - the other electrode is the outer surface of the globe. When you touch
the surface, you make a better connection for the energy to run to the Earth, so plasma globes
light up more where you touch them on the surface.
Sun: There is another form of plasma that we take for granted every day. That’s the
sun. There is so much energy being released by the sun that the matter the sun is made
of is no longer a gas. It is a plasma.
Extensions
Here are some other, more advanced forms of plasma. Prerequisite: a basic understanding of magnetic
field lines, and knowledge of the Earth’s magnetic field.
Solar Wind: The plasma from the sun boils off into space expanding outward.
The this haze of plasma still has a lot of energy and moves away from the
sun on average 400meters/second. The solar wind is still matter in a plasma
state, and there are many fantasy stories written about “solar sailing ships”
with huge sails that catch the solar wind. The sailing ship in Disney’s Treasure
Planet was a solar sailing ship.
Solar flares: Solar flares are tendrils of plasma from the sun that arc and snap
outward from the surface. The different layers of the sun rotate at a different rate
than it’s magnetic field does, and this causes the the magnetic field to twist and
eventually to break. The snapping of the magnetic field releases a tremendous
amount of energy in the form of a solar flare. Solar flares eject a huge burst of
solar winds. Though you may not see the solar winds hitting the Earth, they are so
full of energy that they can even disrupt cell phone service.
Arora Borealis: Also known as The “Northern Lights” come from the solar winds. The magnetic field around the Earth shields us from the solar
winds, buffeting them back like an umbrella. But just as the rain drips
off of the umbrella, the solar winds slide along the magnetic field and collect where the magnetic field comes together at the north and south poles.
Northern Lights can be particularly bright and beautiful right after a
solar flare, when the extra solar winds reach the Earth.
Lighting: Humans have many uses for plasma. Most often, we use it
for light. Most lights are either incandescent (uses a tiny filiment, a thread, heated so hot
it glows, but it’s not plasma), LED (which is a diode that releases energy primarily as light,
with very little heat) or with plasma. Plasma lighting includes neon, high and low pressure
sodium lights (the orange lights in parking lots), fluorescent lights, and compact fluorescent
lights. Most often, the plasma releases a lot of light as ultraviolet - a light we cannot see. So
those lights are coated with a phosphor that absorbes the UV and emits visible light.
Plasma welding: Plasma is also used to weld metal together because it is such a strong
form of energy. One electrode is attached to the metal with a clip. The other electrode
is held in the welder’s hands, slightly above the surface of the metal. When a switch
is depressed, the plasma flows from the welder’s electrode, through the metal, and out
the other electrode clip. It is useful because plasma is far hotter than a flame, and is
focused, so the rest of the metal doesn’t get as hot. The plasma is so bright, the welder
can get a sunburn, even through a T-shirt, and must wear eye protection. Welding can
be done with a flame as well, but it is more difficult and slower.
Tesla coil: Nicola Tesla did many experiments with alternating current -- electricity that moves back and forth like waves. He created a special coil, called
the Tesla Coil, that amplifies the electricity so much that it creates lightening.
Omega Recoil, a performance group of Bay Area artist/engineers, built a 1 million volt Tesla coil. They have also built a very special suit that protects
them from the plasma, so they are able to get struck by the lightingfrom
their tesla coil. They put on performances at special events around the Bay
Area, and have been on TV. (The suit is not strong enough to get struck by
real lighting - it would be vaporized and the wearer would die in an instant!)