Kids: Is fire a gas?
Photo: Flickr user max's pixs
Even though you learned long ago not to touch fire, you might still wonder what it’s made of. Is a flame a solid, liquid, or gas…or some mixture?
The ancient Greeks thought that fire was a basic element, something fundamentally different from earth, air, and water. Modern scientists see fire differently. It is indeed just a gas – much as air is a gas – although the gases of flames are much hotter than ordinary air. Flames are the result of a chemical reaction – usually between oxygen from the air and a fuel like wood or gasoline. The hot gases in the resulting flame are made up of different substances, such as carbon dioxide and steam. So, whether the fuel is a solid (such as wood), a liquid (such as gasoline), or a gas (such as methane), the resulting flame is a gas.
But the flame isn’t entirely gas – the chemical reaction also produces the light and heat that’ve made fire a source of wonder for centuries.
Also, if a flame is hot enough then it can be an ionized gas – known as plasma. That’s what stars are made of. So the Greeks were wrong about earthly fire, but they were right about heavenly fire – the light of stars. This sort of “fire” exists as plasma – a state of matter distinct from solids, liquids, or gas.
