I Understanding Plasma: Definition, Properties, and Temperature Considerations

[physics user1]

So, on wikipedia is said that a plasma is an ionized gas, just that, but when we think about plasma we think that is hot, so here's the question:

What is the right definition of plasma?

Does being a ionized gas also imply being hot and then saying only that is an ionized gas is enough?

I mean can a ionized gas exist at the standard temperature of 300 K?

Since a plasma is a blob of electrons and ions once they get cooled they loose kinetic energy and tend to bond again forming atoms right?

 

[ProfuselyQuarky]

So, on wikipedia is said that a plasma is an ionized gas,

That is the correct definition of plasma. Plasma does not have to always be hot. It can be cold, too.

 

[physics user1]

That is the correct definition of plasma. Plasma does not have to always be hot. It can be cold, too.

But how can it be cold if the ions and the electrons recombine if there is not enough energy?

 

[ProfuselyQuarky]

But how can it be cold if the ions and the electrons recombine if there is not enough energy?

Not sure what you mean. The ions and electrons don't recombine. Nonthermal plasma is partially ionized gas. Most of the energy is stored in the free electrons and the overall temperature of the plasma is low.

 

[physics user1]

Fire is a cold plasma?

 

[ProfuselyQuarky]

Uh, fire isn't actually plasma, at all. I've heard a bunch of (seemingly) knowledgeable people say opposite things, but fire is not plasma.

http://www-spof.gsfc.nasa.gov/Education/FAQs7.html#q97

 

[physics user1]

Uh, fire isn't actually plasma, at all. I've heard a bunch of (seemingly) knowledgeable people say opposite things, but fire is not plasma.

http://www-spof.gsfc.nasa.gov/Education/FAQs7.html#q97

Thanks :)

 

[physics user1]

Not sure what you mean. The ions and electrons don't recombine. Nonthermal plasma is partially ionized gas. Most of the energy is stored in the free electrons and the overall temperature of the plasma is low.

But, if you have a plasma, and you freeze it, don't the electrons recombine forming atoms and then returning to gas?

 

[Drakkith]

But, if you have a plasma, and you freeze it, don't the electrons recombine forming atoms and then returning to gas?

Freezing is a specific phase transition, when a liquid turns into a solid. However you are correct that if you lower the temperature of the plasma the electrons will recombine with the ions/atom to form a gas.

Note that there is a difference between a cold and a hot plasma. I don't know the details, but I'd guess the "cold" plasma is only cold relative to a fully ionized plasma which is "hot". A cold plasma is not cold enough to recombine.

 

[physics user1]

So, here is the point, how can a plasma be cold if once you low the temperature (by saying freezing I was meaning cooling) it return to gas?

Using electric fields to leave the ions and electrons separated?
Is this right?

 

[Drakkith]

I edited my post to explain what I know on that (which isn't much). Not sure if you saw it or not.

 

[physics user1]

I edited my post to explain what I know on that (which isn't much). Not sure if you saw it or not.

Yes I just saw it thanks :)

 

[TheDemx27]

Uh, fire isn't actually plasma, at all. I've heard a bunch of (seemingly) knowledgeable people say opposite things, but fire is not plasma.

From your link: "To create a plasma takes more energy, and requires a higher temperature than the flame provides. The collisions between atoms need to be energetic enough to kick an electron completely out of the atom."

 

[shjacks45]

So, on wikipedia is said that a plasma is an ionized gas, just that, but when we think about plasma we think that is hot, so here's the question:

What is the right definition of plasma?

Does being a ionized gas also imply being hot and then saying only that is an ionized gas is enough?

I mean can a ionized gas exist at the standard temperature of 300 K?

Since a plasma is a blob of electrons and ions once they get cooled they loose kinetic energy and tend to bond again forming atoms right?

Note that ionized Lithium is an atom whereas ionized Hydrogen is a proton. An alpha particle (or He+2) is also a bare nucleus.