I had this question from the day (9 years old, now 16) that I learned about states of matter. I have asked many of my teachers, some of them told me it's a gas some that it's a plasma. Can anyone answer my question?

Recently I've learned that the plasma state is obtained when all the electrons from the atom are removed. Obviously it's present in the sun due to high temperatures.

  • $\begingroup$ This is cross posted on Physics.SE physics.stackexchange.com/questions/94609/… $\endgroup$ – user4076 Jan 21 '14 at 10:25
  • $\begingroup$ Yes I did. Because this topic belongs to both physics and chem. And what's wrong with that. $\endgroup$ – Akshay Nagraj Jan 21 '14 at 10:29
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    $\begingroup$ You could at least point it out in the question, because then the answerer may look at the other answers to see if the question has already been sufficiently answered. $\endgroup$ – tschoppi Jan 21 '14 at 10:31
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    $\begingroup$ @user37419 Also, a cross posted question should be written to specific suit the audience on the sites it is posted on. Also, you might want to read the faq about cross posting meta.stackexchange.com/questions/64068/… $\endgroup$ – user4076 Jan 21 '14 at 10:33

A candle flame is the product of the oxidation of wax to $\ce{CO2}$ and other small organic compounds. Since these small compounds are energetically lower, energy is released during the reaction, in the form of light and heat. So really, we start out with gas.

However, flames can also conduct electricity, and the conductivity varies with the location in the flame. The linked science fair project summary states that the lowest resistance (highest conductivity) was found at the edge of the bright yellow part of the flame the conductivity was the largest, meaning that the concentration of ions was the highest. The lowest resistance value found was $80~\Omega$, which is still very large in comparison to the resistance of plasma, which is generally considered to be $0$.

So, summarizing my answer: A flame is a gas with lightly ionized portions, but does not qualify as a real plasma.

  • $\begingroup$ Ok, can you tell me how did you get to know about science fair and all. Is it from web or from newspaper. And also in plasma state the electrons are removed from the atoms right, then where will the go in sun? $\endgroup$ – Akshay Nagraj Jan 21 '14 at 10:34
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    $\begingroup$ I googled "flame conductivity" and skimmed for something useful. The fouth entry did it for me. In a plasma, not all electrons are removed from the atoms. As to solar reactions, that would make a good additional question: "Where do the electrons from the solar plasma go to?" Feel free to open a new question about that ;) $\endgroup$ – tschoppi Jan 21 '14 at 10:38
  • $\begingroup$ Why don't you answer it here itself? $\endgroup$ – Akshay Nagraj Jan 21 '14 at 10:41
  • $\begingroup$ Because the sun has almost nothing to do with a candle flame, and because the question you asked really only referred to a flame. Also: One question per question ;-) It keeps things clearer. $\endgroup$ – tschoppi Jan 21 '14 at 10:44
  • $\begingroup$ While a candle flame is not a plasma, it is a fairly low energy, low temperature flame. In really hot flames, would you classify the state as more like a plasma than a gas? $\endgroup$ – matt_black Jan 21 '14 at 15:40

A gaseous flame is hot gas seeded with free radicals and ionized species, a dilute plasma. Note that solid flames exist. Mix finely divided nickel and aluminum, tantalum and graphite, etc., compress into a compacted body, and heat an edge very hot until things start. A white hot interface propagates through the body as the components react. I would hesitate to call that a condensed phase plasma.


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