On March 2, scientists were asked to answer the question "What is a flame?" in a way that an 11-year-old would understand. More than 800 entries were received in the Flame Challenge, which was sponsored by the Center for Communicating Science at Stony Brook University. A panel of 11-year-olds selected these finalists. The winner will be announced June 2.
Richard Frauenglass, a retired engineer, of Huntington:
What is a flame? A flame is an object, a "thing," something you can see, something you can touch (but don't do that because it is hot). It is not like other objects such as a rock because it "happens" and then goes away.
It "happens" when something (a "combustible") is heated to a high enough temperature and then starts to burn. This might be wood, or paper, or gas, or oil, or dry leaves, just to name a few. It takes different amounts of heat to get them to burn but they all do. The big name for things burning is "combustion." You get the heat by burning something else or -- if you have a magnifying glass and focus sunlight on a single spot -- you will be able to burn paper and some other things.
There are other ways to make a flame by mixing chemicals but heating is easiest to understand.
When something burns it changes into ash and/or a gas ("residue"), and light. This light is what is called "a flame."
So a flame is what you see when something burns.
Nathan Anderson, a fuels analysis and certification engineer in Seattle:
To have a flame, you need three very important things: You need fuel (the stuff that burns), air (the stuff you breathe and more precisely the oxygen in the air), and heat to start the flame (often times another flame, matches, lighters, or if you are really good two sticks!). The easiest way to think about flames is to imagine a candle being lit by a match. The most important thing is to realize that flames are all about gasses! That's why flames flicker, dance, and seem to float above the thing they are burning, because they actually are!
When you light a candle with a match the flame from the match melts the wax around the wick turning it into a liquid, that liquid is then sucked up the wick (like watching water climb up a dry paper towel!) and the flame from the match boils the liquid in the wick and turns it into a gas! The newly created gas (that used to be a solid candle) then floats away from the wick like steam rising from a boiling pot and mixes into the air. When the wax (that is now a gas), the oxygen in the air, and the heat from match are all together then a new flame starts!
The cool thing about a flame is that the real flame is very, very small! Only a small part of the flame you see is actually on fire, and that's because fire is very, very picky. Think of it as Goldilocks -- too much fuel and it won't burn, too much air and it can't burn, it has to be just right and that only happens right at the outer rim of the flame. The rest of the flame, inside of that rim, is just full of hot gas! As the flame burns, it has to get new fuel, so the solid wax continues to melt and get pulled up the wick. Once the wax boils off the wick and pushes out towards the fire, it gets hotter and hotter as it goes until it too bursts into fire. As the wax gets hotter it starts to glow, just like metal does when it gets too hot. The hotter the wax gas gets, it changes colors -- that's why you see yellows, and oranges, and reds in the flame. If you look really close at a flame you'll even see blues and whites! Sometimes the wax moves so fast as it heads to little fire that it can't get burnt all the way so it escapes as shoots off into the air. That's what soot and smoke are, really fast moving bits of wax! Think of them as burnt marshmallows. The outside is all black, but they are still marshmallows on the inside. Smoke is still wax, just a little overdone.
Rachel D'Erminio, a media arts teacher, and Ted Londner, an aerospace engineer, in Cambridge, Mass.
Ben Ames, a graduate student in experimental physics (quantum optics and spectroscopy) at the University of Innsbruck, Austria
Simon Schreier, a graduate student in plant and environmental science in Central, S.C.