PLASMA STATE: CHARACTERISTICS, TYPES AND EXAMPLES - CHEMISTRY - 2025

The plasma state is one of the fundamental ways in which matter can aggregate, and it is the most predominant in the observable Universe. Plasma consists of a hot, bright and highly ionized gas, to a point where it acquires unique properties that differentiate it from the gaseous state or any other gas in particular.

We see the plasma scattered in the stars of the night skies. As there are an endless number of stars in the Universe, as well as nebulae and other celestial entities, it is considered the most important state of matter. On Earth it is considered the fourth state, after liquid, solid and gaseous.

Plasma lamp

The Sun is the closest example where we can appreciate the characteristics of plasma in a natural environment on massive scales. On the other hand, natural phenomena occur on Earth in which a momentary appearance of plasma is triggered, such as fire and lightning in storms.

Plasma is not only associated with high temperatures (millions of kelvin degrees), but also with great electrical potentials, incandescent lights, and infinite electrical conductivity.

Plasma characteristics

The plasma of stars and nebulae makes up practically the entirety of the observable Universe. Source: Pxhere.

Composition

Matter is composed of particles (molecules, atoms, ions, cells, etc.), which, depending on the effectiveness and the forces with which they are added, establish a solid, liquid or gaseous state.

Plasma particles consist of positively charged atoms, better known as cations (+), and electrons (-). In the plasmatic state of matter there is no talk of molecules.

The cations and electrons vibrate at very high frequencies showing a collective and not individual behavior. They cannot separate or move without the entire set of particles being disturbed.

This does not happen for example with gases, where their atoms or molecules, although they collide with each other, have minimal, negligible interactions.

Training

The plasma state is formed mainly when a gas ionizes as a result of its exposure to very high temperatures.

Let's start with an ice cube first. This is a solid. If heated, the ice will melt into liquid water. Then, by heating to higher temperatures, the water will begin to boil and escape from the liquid as vapor, which is a gas. So far we have the three best known states of matter.

If the water vapor is heated to a much higher temperature, under favorable conditions there will come a time when their bonds will break to form free oxygen and hydrogen atoms. Then the atoms absorb so much heat that their electrons begin to shoot out into the surroundings. Thus, oxygen and hydrogen cations have been formed.

These cations end up wrapped in a cloud of electrons, added by the action of the community and electrostatic attractions. It is then said that a plasma has been obtained from the water.

In this case, the plasma was formed by the action of thermal energy. However, highly energetic radiation (gamma rays), as well as large differences in electrical potentials, can also induce their appearance.

Quasineutrality

Plasma has the characteristic of being quasineutral (almost neutral). This is because the number of electrons excited and released from the atoms tends to be equal to the magnitudes of the positive charges of the cations. For example, consider a gaseous calcium atom that loses one and two electrons to form the cations Ca ⁺ and Ca ^2+, respectively:

Ca (g) + Energy → Ca ⁺ (g) + e ^-

Ca ⁺ (g) + Energy → Ca ²⁺ (g) + e ^-

Being the global process:

Ca (g) + Energy → Ca ²⁺ (g) + 2e ^-

For every Ca ²⁺ that is formed there will be two free electrons. If there are ten Ca ²⁺, then it will be twenty electrons, and so on. The same reasoning applies for cations with higher magnitudes of charge (Ca ³⁺, Ca ⁵⁺, Ca ⁷⁺, etc.). Calcium cations and their electrons become part of a plasma in a vacuum.

Physical properties

Plasma generally appears to be a hot, glowing, highly electrically conductive liquid gas that responds to or is susceptible to electromagnetic fields. In this way, plasmas can be controlled or locked up by manipulating a magnetic field.

Types of plasma

Partially ionized

A partially ionized plasma is one in which the atoms have not lost all their electrons, and there may even be neutral atoms. In the example of calcium it could be a mixture of Ca ²⁺ cations, Ca atoms, and electrons. This type of plasma is also known as cold plasma.

On the other hand, plasmas can be contained in containers or insulating means that prevent the diffusion of heat to the surroundings.

Fully ionized

A fully ionized plasma is one in which its atoms are "naked", since they have lost all their electrons. Therefore, its cations have high magnitudes of positive charge.

In the case of calcium, this plasma would be composed of Ca ²⁰⁺ cations (calcium nuclei) and many high-energy electrons. This type of plasma is also known as hot plasma.

Examples of plasma

Plasma lamps and neon lights

Plasma lamps offer a safe and close view of how this state of matter behaves. Source: Pxhere.

Plasma lamps are artifacts that adorn any bedroom with ghostly lights. However, there are other objects where we can witness the plasma state: in the famous neon lights, whose noble gas content is excited by the passage of an electric current at low pressures.

Ray

The rays that fall from the clouds are a momentary and sudden manifestation of the terrestrial plasma.

Solar storms

Some "plasma particles" are formed in the ionosphere of our planet by the constant bombardment of solar radiation. In the flares or whips of the Sun we see huge amounts of plasma.

Aurora borealis

Another phenomenon related to plasma is observed at the Earth's poles: the northern lights. That fire with icy colors reminds us that the same flames in our kitchens are another routine example of plasma.

Electronics devices

Plasma is also part, in smaller proportions, of electronic devices such as televisions and monitors.

Welding and science fiction

Examples of plasma are also seen in welding processes, in laser beams, in nuclear explosions, in Star Wars lightsabers; and generally speaking, in any weapon that resembles a destructive energy cannon.

References

1. Whitten, Davis, Peck & Stanley. (2008). Chemistry (8th ed.). CENGAGE Learning.
2. Plasma Science and Fusion Center. (2020). What is plasma? Recovered from: psfc.mit.edu
3. National Center for Atmospheric Research. (2020). Plasma. Recovered from: scied.ucar.edu
4. Helmenstine, Anne Marie, Ph.D. (February 11, 2020). What Is Plasma Used For, and What Is It Made Of? Recovered from: thoughtco.com
5. Wikipedia. (2020). Plasma (physics). Recovered from: en.wikipedia.org