“Keep a little fire burning

However small, however hidden”

                                                                             Cormac, Mc Carthy, the Road

Sitting around a Campfire, You can feel its heat, smell the woody smoke, and hear it crackle. If you get too close, it burns your eyes and stings your nostrils. You could stare at the bright flames forever as they twist and flicker in endless incarnations. But what exactly are you looking at?

Fire
Fire

The flames are not obviously – Solid, not are they liquid Mingling with air. They are more like a gas but more visible and more fleeting and on  a scientific level. Fire differs from gas because gases can exist in the same state indefinitely while fires always burn out eventually.

One misconception is that fire is a Plasma, the fourth state of matter in which atoms are stripped of their electrons. Like Fire and unlike the other kinds of matters, Plasmas don’t exist in a stable state on earth.

They only form when gas exposed to an electric field or super-heated to temperatures of thousands of tons of thousands of degrees. By Contrast, Fuels like wood and paper burn. At a few hundred degrees – Far below the threshold of what’s usually considered a plasma. So if fire isn’t a solid, liquid gas or a plasma, What does that leave?

It turns out fire isn’t mattered at all. Instead, it’s our sensory experienced of a Chemical reaction called Combustion.

In the way, Fire is like the leaves changing color in fall, the smell of fruit as it ripens, or a firefly’s blinking light.

All of those are so sensory clues that a Chemical reaction is taking place. What differs about fire is that engages a lot of our senses at the same time creating the kind of vivid experience. We expect to come form a physical thing. Combustion creates that sensory experience using fuel, heat, and oxygen.

In a campfire, when the logs are heated to their ignition temperature. The walls of their cells decompose, releasing sugars and other molecules into the air.  These molecules then react with airborne oxygen to create carbon dioxide and water.

At the same time, any trapped water logs. Veporizes expands, retures the wood around it and escape with a satisfying crackle. As the fires heat up, the carbon dioxide and water vapor created by combustion expand. Now that they are less dense they rise in a thinning column. 

Gravity causes this expansion and rising which gives flames their characteristic taper without gravity, molecules don’t separate by density and the flames have a different shape.

We can see all of this because Combustion also generates light. Molecules emit light when heated and the color of lights depends on the temperature of the molecules. 

The hottest flames are white or blue. The type of Molecules in a fire can also influence flame color. For instance, any unreacted carbon atoms from the logs from little clumps of soot that rise. Into the flames and emit the yellow-orange light we associate with a campfire.

Colored flames
Colored flames

Substances like Copper, Calcium Chloride and Potassium chloride can add them. Own characteristic hues to the mix. Besides colorful flames, fire also continues to generate heat as it burns. This heat sustains the flames by keeping the fuel at or above ignition temperature. Eventually, though, even the hottest fires run out of fuel or Oxygen.

 

Then, those twisting flames give a  final hiss and disappear with a wisp of smoke as if they were never there at all.

I hope you understand the concept of Fire. Please share this knowledge with your friends and relatives. You also read my more very interesting and informative blogs.