MadSci Network: Chemistry

Re: What is the temperature of the cooking range flame?

Date: Fri May 29 22:17:38 1998
Posted By: Michael Weibel, Grad student Chemistry/Physics, University of Utah
Area of science: Chemistry
ID: 896199816.Ch


To answer your second question (about the temperature of a candle flame), 
check out the most recent chemistry archives section, where that exact 
question was asked a few weeks ago.  If you have further questions about 
his response, I'd suggest emailing him.

As for your question about the propane and/or butane flame...the answer is 
that they are hot.  If you combust either chemical in air (approx 20% 
oxygen, 79% nitrogen and 1% argon, where oxygen is the material which 
affects the flame's temperature), you "oxidize" the material.  What is 
happening is that you are turning molecules with a lot of energy in their 
bonds (propane or butane) into ones with less energy in their bonds (carbon 
dioxide and water).  As such, the excess energy is given off in the flame. 
Hydrocarbons (molecules containing both the elements hydrogen and carbon 
only) are generally full of energy and make good fuels (because of the 
large amount of energy that can be liberated).  If you don't have oxygen 
present, you don't get as much energy liberated, because your products 
(probably hydrogen gas and carbon soot) aren't as low in energy.

I don't know for sure (although the person that answered the candle 
question probably does), but I'd say that the flame temperature is probably 
about 2500 degrees Fahrenheit.  You'd never attain that temperature, 
though.  The reason you can't heat an object up to that temperature is that 
air cools things.  As you are trying to get a pan or pot to that 
temperature, collisions with air molecules remove heat from the object 
being heated, so that there is a balance between heating and cooling 
(that's why a hot pot rapidly cools when the flame is removed).  
Additionally, if there is something in the pot (like water, for example), 
then the temperature of the system (pot and water) won't go above the 
boiling point of the water until all of the water is boiled away (that is, 
all energy goes into vaporizing the water, and not in raising the 
temperature of the system).

I know that I didn't say a lot about the temperature of the flame per se, 
but I think that the background info is useful.  

Please feel free to email me if you have further questions

Best Regards,

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