What is fire? 1

[Unotec]

I had my 5 year old asking me if fire is solid, liquid or gas.... I couldn't answer.

What would your answer have been?

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[TheTick]

Fire good!

 

[Unotec]

ok, so if fire is gas, then if I add enough heat to it, it would glow, correct?

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[cranky108]

Back with the gas thing. I would say it is closer to a plasma.
I say this by the way it conducts electricity.

 

[rb1957]

"ok, so if fire is gas, then if I add enough heat to it, it would glow, correct?" ... no, fire is heated gas ... the gas is air, well, air minus a bunch of the O2 and plus a bunch of CO2. i'd've thought that someone in the chemical business would've appreciated that fire is a chemical reaction between the fuel (wood, paper) and the O2 in the air. when there's not enough heat you get incomplete combustion (ie smoke) ... well that my 2c worth

 

[Unotec]

rb1957, I agree that fire is the RESULT of a chemical reaction, but not always fuel and O2, is it? And if fire is heated gas and I heat gas (not necessarily through combustion) why would it not glow if fire is nothing but heated gas?

As someone in the chemical business might appreciate, there are several exothermal reactions that do not require the O2 in the air. Such might be the case of Magnesium and water. And there are several more.

Cranky, I did not know fire conducted electricity, quite interesting. But so do many other gases. This characteristic not necessarily makes it plasma, does it? I had an initial thought that fire could be plasma, but then inclined more into the gas theory.

Ok, I guess I was not the only one that could not answer to a 5yr old!

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[BrunoPuntzJones]

Fire is rapid oxidation of a material, which gives off heat, gases, and light.

Flame, which is what some people are trying to define here, is the visible manifestation of (some) fire. It can be a plasma, depending on the temperature and gases involved, it can also just be very hot (un-ionized) gases.

 

[cranky108]

They don't usually give conduction of electricty as feature of a plasma in school. But it is a problem with power lines when brush fires are about.

Also I discovered this when I was younger with a light match and a bug zapper.

 

[BrunoPuntzJones]

I wouldn't have much to do if plasma wasn't conductive. I work for a magnetron sputtering thn film company.

 

[btrueblood]

Does a sputtering magnetron sound like an electronic Porky Pig?

 

[rb1957]

thx btb ... still laughing at that one !

 

[drawoh]

Unotec,

I would say that flames are a gas, heated to the point of glowing. How you heat the gas is not relevant. It can be a match. It can be the sun.

You will have to explain somehow that hot things glow, and that they glow a certain colour at a certain temperature.

JHG

 

[photoengineer]

"that hot things glow"

Cold things glow too. Just not at a wavelength we can see.

(Hence...night vision goggles.)

Cedar Bluff Engineering

http://cedarbluffengineering.webs.com

 

[rb1957]

what if the fuel is natural gas ?

 

[cranky108]

Cold things glow? Really.

I thought night vision gogles worked off low light provided from other sources. Do they work in underground conditions?

I remember burning alcohol in chemistry class, and there was no visible flame. It did however burn my lab partners hand.

 

[photoengineer]

"Cold things glow"

Sure, why wouldn't all objects (that have a temperature above absolute zero) emit radiation? Hot objects emit radiation in the visible light range. Colder objects emit radiation that is of a longer wavelength.


Cedar Bluff Engineering

http://cedarbluffengineering.webs.com

 

[Techne]

Unotec, bodily heat does give off light, only that it is in the infrared spectrum and not the visible light spectrum.