Plasma: The Fourth State of Matter?

We all know that everything in the universe which occupies space- except for the mysterious dark matter which covers 85% of the universe- exists as one of the three states of matter: solid, liquid or gas. But what if I told you that there is another state of matter-plasma?

Electrically charged gas, or plasma, is actually the most abundant state of matter. 99% of all matter in the universe- except for the above mentioned dark matter- exists as plasma. From intergalactic medium (space between galaxies) to those funky neon signs, plasma is everywhere.

But what exactly is plasma? And how is it created? Plasma is created when gases are heated at very high temperatures. We know that according to the Kinetic Particle Theory, the higher the temperature, the higher speed of the particles of a substance and thus more the collisions between them. Therefore in plasma, atoms of the heated gas move at such high speeds that they knock off valence electrons (those at the last shell) when they collide with each other. Thus plasma is a mixture of positive ions (formed because of the atoms now have more positively charged protons than the negatively charged electrons) and free electrons. Plasma is called partially ionised if a high number of neutral particles are present, for example the plasma created by lightning strikes, which also an example of plasma being made by high voltage electricity. Due to the high heat energy required to create plasma, it exists more abundantly on stars, and Earth contains a low amount of plasma.

In the layers above the earth’s atmosphere, including the thermosphere, exosphere and mesosphere, plasma exists mixed with other gases which are present there. The ionosphere, a layer ionised by solar radiation, contains plasma due to ultraviolet rays from the sun. Most particles in the Earth’s magnetosphere (Earth’s magnetic field) are ionised plasma.

We can observe plasma on Earth. In the magnetosphere, plasma sometimes flows to the North and South Poles of the Earth and as the fast-moving plasma particles collide with the gases in the atmosphere, they glow to form the Aurora Borealis or Australis (Northern or Southern Lights)- one of the infamous ethereal sights in the polar regions.

In the colourful neon signs we see on shops, electricity converts the neon gas in the tubes into glowing partially ionised plasma, producing the ‘neon light’. Electricity in fluorescent lights also creates plasma.

Plasma was first discovered by the British chemist Sir William Crookes in 1879, as “radiant matter” when he ionised air by applying high voltage through a voltage coil. The term “plasma” was coined by the American chemist and physicist Irving Langmuir in 1928, as it reminded him of blood plasma (one of the major components of blood).