The Fourth State of Matter
A brief introduction to Plasma
We are all familiar with the three states of matter taught in grade school science, but what about the elusive fourth state that we hear from time to time. In this article, we will take a deeper look at plasmas (not the one found in blood), what it is and where to find it.
The First Three States
Before looking at plasma, it would be prudent for us to read up about the three states of matter - solid, liquid and gas. All these states consist of atoms and molecules although they differ in the intermolecular strength betweens these particles. Below is a quick recap of the three states.
Solid: A material whose atoms are strongly bounded together, with atoms only able to vibrate about a fixed position.
Liquids: A material with weaker attractive forces between atoms and molecules. The atoms/ molecules are still somewhat attached together and will take the shape of the container it is in.
Gases: A material in which atoms or molecules have negligible intermolecular forces of attractions. These atoms/ molecules are completely separated from each other and can move around at high speeds.
Seeing as the main difference amongst the three states are mostly due to the difference in intermolecular forces of attractions, the phase changes between them are thusly very well defined. To change from solids to liquid and from liquid to gas requires one to merely heat up the material and vice-versa (of course the actual amount of heating required differs by material).
Plasma
What exactly is Plasma? One can think of it as a hybrid of liquid and gas. Plasma is essentially a gas-like fluid in which the particles lose their electrons to become positively charged ions. However the electrons are still considered part of the plasma structure, therefore plasma is generally considered an electrically quasi-neutral1 medium. The presence of these charged particles also makes plasma highly conductive of electricity - a defining trait of plasma!23
Apart from its electrical conductivity, another key difference between air and plasma is the way the particles move. Recall earlier on, it was mentioned that air particles are separate and able to move around freely at high speeds. However, since plasma is made up of charged particles, their movement generates electric current. This means that each particles’ movement is affected and affects other particles.
Applications of Plasma
Unlike many ‘exotic’ objects that one comes across in the study of science (and astrophysics in particular), plasma is actually more common that one might assume. Plasma can actually be found in everyday items like plasma TV, neon signs and fluorescent lamps.4 Another common occurrence of plasma actually happens during space shuttle re-entry. During re-entry, due to the extreme speed of the space shuttle as it collides with the air molecules within our atmosphere, it actually heats up nitrogen enough such that plasma is formed on the space shuttle’s heat shield.
Creating Plasma
Much like the first three states, where to induce a phase change (i.e. from solid to liquid etc..), one simply needs to heat up/ cool down the substance. Plasma’s relationship with the other three states function in a similar way. Plasma can be created simply by heating a gas to extremely high temperature such that its constituent atoms and molecules split apart into the required ions and electrons. However, the energy needed to heat the gas to such an extreme temperature makes it only feasible in space or in a laboratory.
Plasma is quasi-neutral because it is generally considered neutral but its actual charge may differ
Chen, Francis F. (1984). Introduction to Plasma Physics and controlled fusion. Springer International Publishing. pp. 2–3. ISBN 9781475755954. Archived from the original on 15 January 2018.
Freidberg, Jeffrey P. (2008). Plasma Physics and Fusion Energy. Cambridge University Press. p. 121. ISBN 9781139462150. Archived from the original on 24 December 2016.
IPPEX Glossary of Fusion Terms Archived 8 March 2008 at the Wayback Machine. Ippex.pppl.gov. Retrieved on 2022-04-17.