What is Plasma? The Fourth State of Matter Explained

What is Plasma? The Fourth State of Matter Explained

Plasma is often called the fourth state of matter and makes up 99% of the visible universe.

But what exactly is plasma? Let's explore the properties of plasma and how it differs from the solid, liquid, and gas states of matter.

What is Plasma?

Plasma is an ionized gas consisting of positive ions and free-floating electrons. To create plasma, energy must be added to gas particles to strip electrons away from atoms or molecules, leaving behind a soup of positively charged ions and negatively charged freefloating electrons.

This process is called ionization and gives plasma unique properties not seen in solids, liquids, or regular gases. Plasma conducts electricity and is affected by electric and magnetic fields since it contains charged particles. At the same time, it remains heterogeneous like a gas since the electrons are not bound to the ions.

Plasma has such interesting behavior because of the electric charge separation between its ions and electrons. The electric forces influence how plasma behaves in electric and magnetic fields. However, the overall plasma remains quasimetric since the positive and negative charges balance out.

The Fourth State of Matter While traditionally there were three states of matter - solid, liquid, and gas - plasma deserves recognition as the fourth state of matter due to its unique properties.

Solids have a definite shape and volume due to the structure of their atoms or molecules.

Liquids have a definite volume but flow and change shape easily since their atoms or molecules can move around one another.

Gases have no definite shape or volume and expand to fill their container. Their atoms or molecules move rapidly and independently.

Plasma, like gas, has no definite shape or volume. However, it differs because the ions and free electrons within interact mainly through electric and magnetic fields rather than through collisions as in a gas.

Plasma is by far the most common form of ordinary matter in the universe, accounting for 99% of its visible mass. The many unique properties and wide prevalence of plasma have led to its designation as the fourth state of matter.

How is Plasma Formed?

There are a few main ways that plasma can be produced: Through heating - As gas is heated to very high temperatures, the atoms or molecules may gain enough energy from collisions that they split into ions and electrons. This is how plasmas are formed in stars and many industrial processes.

Through reduction of pressure - At low pressures, if the mean free path of gas molecules or atoms is long enough, ionizing collisions with electrons can occur. This allows plasmas to be generated in vacuum tubes.

Through the application of strong electric or electromagnetic fields - If the field is strong enough, electrons may be stripped from neutral gas particles through the field effect alone. This includes plasmas formed in fluorescent light bulbs and plasma TV screens.

Through the introduction of radiation - High-energy photons like X-rays or gamma rays carry enough energy to free electrons from neutral gas molecules when they encounter them, resulting in plasma formation.

One notable example of plasma formation is lightning. The rapid heating and electromagnetic forces within a lightning bolt ionize the surrounding air, creating an electrically conductive plasma channel.

Properties and Behavior of Plasma

Plasma demonstrates several properties that make it distinct from the other states of matter: Collective behavior - Due to long-range electric forces between charged particles, plasmas exhibit collective behavior. An isolated particle does not move independently of others.

Debye shielding - Nearby plasma particles of opposite charge are attracted to each other, screening the long-range electric fields within the plasma. This gives rise to a phenomenon called Debye shielding.

Quasi neutrality - The electric charge of the plasma as a whole is approximately neutral due to equal numbers of positive and negative charge carriers.

Free electrons - Electrons act as individual particles in the plasma due to the high temperature, interacting through long-range electromagnetic forces rather than short-range nuclear forces.

Plasma frequency - Plasmas can oscillate coherently at the plasma frequency, an inherent property dependent on charge density.

Conductivity - Plasmas conduct electricity since they contain free electrons that can flow through the material in response to electric fields.

Plasma parameters - Quantities like the plasma density, temperature, and velocity describe the macroscopic collective behavior of plasmas.

Applications of Plasma Due to its unusual conductive properties influenced by electromagnetic fields, plasma has many applications across industries: Manufacturing - Plasma cutting, welding, and 3D printing use an energetic plasma jet to shape materials. It's used to make car parts, spacecraft components, and more.

Electronics - Plasma displays like plasma TVs and some neon lighting use small, localized plasmas to illuminate pixels or tubing. Fluorescent lights also use plasma.

Medicine - In dermatology, cosmetic surgery, and dentistry procedures often use plasma jets to precisely remove diseased tissue or reshape features.

Spacecraft propulsion - Hall-effect plasma thrusters use low-temperature plasma to propel satellites and spacecraft. They provide high efficiencies and specific impulses.

Fusion power - The quest for limitless clean energy involves attempts to reliably fuse atomic nuclei inside a plasma discharge, as happens in stars including our Sun. Experimental fusion reactors like r3stemcell attempt to produce and contain plasma hot enough for fusion.

As we continue exploring plasma's unique properties, new applications will continue to emerge across various industries. Its strange yet scientifically consistent behavior makes it a fascinating state of matter.