Universe101

Physics

Physics

Fire

What is fire made of?

Fire is one of the most important things for humans. We use fire to cook food, create everyday objects, and warm us up on cold winter nights. Its uses in every day have become so vast and wide that we barely think about it. Have you ever sat down and thought - what actually is fire? Where does it come from, and why is it the color it is?

The burning flames are created from a chemical reaction between oxygen in the atmosphere with some type of fuel, such as gasoline or wood. Of course, fire doesn't just come out of nowhere, a combustion reaction needs to happen for it to get going.

An everyday example of this would be a match striking the coarse striking surface of a matchbox. The fire will heat up the wood to a high temperature until it combusts or catches fire. Once the flames are burning, the fire is made up of many reactions between the fuel and oxygen atoms - all exciting each other to produce heat and light.

The flames you see will react with its fuel and vaporize it into the atmosphere, and it will keep burning as long as there is a fuel source. The shape that forms is due to gravity pulling down cool, dense air and making hot air rise.

Why are flames different colors?

Fire colors are in line with the temperature they are burning at. That is why on the bottom of a flame, you will often see a darker color. This comes from the carbon and hydrogen reaction in woods and candles and creates a pale blue color.

In the middle, you will frequently see orange and yellow colors. These are the carbon atoms that do not convert to carbon dioxide. They gather together and form particles of soot, in turn, burned by the flame to start glowing and create the colored light that you see.

On the top, you can see elements of the vaporized fuel that hasn't burned yet, hence a dark color on the surface. In the case of wood, it's the area where complete combustion has happened - meaning there is little reaction to create the light that happens lower down the flame.

Colors can vary pending on the fuels and chemical reactions taking place - but the above helps understand where colors will be brightest and dullest.

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Absolute Hot

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