I’ve done a search regarding fire and what state of matter it might be, and have come up with very little. Is there any consensus on what state of matter fire is, or if it is even a state of matter to begin with. Is the flame that I see when I flick my Bic a plasma. I’m not talking about lightning, the sun, a nuclear explosion or the tail of a comet. I’m talking about your typical garden variety flame that one might witness in a campfire.
I’ve done some research online, and come up with mixed results. Some say it’s simply a hot gas mixed with solids, while others say it’s a plasma. So what is fire? Come to think of it, this may actually be a post worthy of Great Debates, but I’ll post it here to be safe.
I hope this isn’t too much of a hijack, but I’m trying to get a better understanding of what a plasma is. The term is a new one since when I was in school, and I’m wondering if there might be a definition for it which fits the pattern of the definitions of the other forms of matter. Namely:
– A solid has a fixed mass, volume, and shape.
– A liquid has a fixed mass and volume, but a variable shape.
– A gas has a fixed mass, but a variable volume and shape.
I’m really not clear on how a plasma is different than a gas, except that it has something to do with ionization. Could this mean that the atoms of a plasma are constantly gaining and losing electrons, so that it would fit in the above list by having a variable mass?
A plasma is just a soup of ions and electrons. “Really Hot Gas” would be a synonym.
You couldn’t say that a plasma had a variable mass. The mass of a single electron is negligible compared to the mass of a nucleus. Gain one, lose one, not much difference.
The difference between gas and plasma is in a gas, each nucleus retains its own electrons, while in a plasma, the electrons are so excited that they don’t stay in orbit around any one nucleus but wander randomly through a “soup” of nuclei and electrons.
Just a nitpick: although gas does become incandescent if it gets hot enough (the Sun, for example), most of the flames we ordinarily encounter aren’t hot enough for the combustion gases themselves to glow. What you see in a candle flame is the glow of minute carbon particles as they flare momentarily before being completely oxidized. The flames we associate with candles, wood fires, etc. might be described as “incandescent smoke”.
Also, plasma colors have narrow precise frequencies, since they’re caused by electrons returning to atoms and dropping down through various energy levels. Neon lamps, glowing argon, sparks in air, etc., produce emission lines. Fire doesn’t (at least not much.)
The color of fire is partly from white hot carbon particles, partly from fluorescence from various chemical reactions.
Since plasma is full of movable charged particles, it’s a fairly good conductor. Fire isn’t. On the other hand, you can spike a flame with various chemicals to fill it with ions and electrons, making it conductive, and producing bright colors.
Here’s a concept: “Dusty plasma.” It doesn’t involve dust. Instead it means that there are a few ionized atoms and electrons, plus lots of cold neutral gas. It’s a “plasma dust” scattered in normal gas. I think fire would usually qualify as a dusty plasma. But when we talk about “plasma”, we usually mean the fully ionized kind.