Plasma physics

Plasma, the fourth state of matter.

The word PLASMA has always been associated to high-end research and new technology development.
In recent times, this word has been let out into the civilian life by the introduction of some plasma technologies in the consumer market.
Plasma is known as the fourth state of matter… what does it mean?

STATO1_solidSTATO2_liquidSTATO3_gasPlasma

 

Matter, as we all studied at school, can be defined as the arrangement of its constituent atoms and their patterns.

Let’s see an example of some well known matter: if we take an ice cube we can feel it is a solid and its atoms are nicely packed together close to each other without much energy to move about. They are arranged symmetrically in periodic repeating patterns.

What happens if we add some energy to this ice cube? The atoms begin to move more freely and are weakly bonded to each other: the ice melts and the liquid takes the shape of the container because this state doesn’t have any associated shape.

What happens if we add even more energy? The atoms of the liquid absorb this energy and become free from any bonds they had: we obtain the the gaseous state. Gas molecules no longer feel the need to stich to each other and they can pretty much wander about in whatever space they get so the boundary now spreads to the whole room.

Remember though that the number of atoms hasn’t changed and if you decide to cool down the whole room you won’t have a room size ice cube but just the ice cube you began with.

Now, what happens if we add energy one more time? We ionize the gas and we finally have a plasma!

Plasma is similar to a gas but it is more free. In plasma, we have ionized the atoms of the gas and instead of a cloud of atoms floating around, you have a cloud of negatively and positively charged particles (electrons and ions) that have a lot of energy. Since these constituents of plasma are charged, they become reactive to an externally applied electric or magnetic field. The way they react depends on the nature of the field we apply. Plasma doesn’t have any shape but can form structures when subjected to certain fields (Plasma globes, welding arcs…).

At each transit stage, energy has been added and has drastically altered the nature of the substance we were working with. In this way we go from tightly packed atoms to atoms that slip and slide beside each other but don’t go far from each other, to atoms that fly everywhere, to atoms that have been broken into smaller bits: these are the different states of matter.

Plasma is called the fourth state of matter because, even if it is not yet known by everybody, it is not difficult to observe in nature:

>> Lightning are plasma

>> Aurora borealis are plasma

>> Fire in a chemical reaction is plasma: when you burn up something, you release a lot of energy; if the fire is hot enough, the gas will ionize and form a plasma.

In sum, the word plasma identifies the name used to refer to any ionised gas.

IONISED GAS = PLASMA

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