The fire burns by forming a flame because it is a chemical reaction called combustion. When the fuel and the oxidizer react in the presence of heat, it generates light and heat, which creates the flame.
Fire is a chemical reaction where a fuel (a material capable of burning, such as wood, paper, or gasoline) reacts with an oxidizer — most often the oxygen contained in the air. This reaction releases stored energy in the form of heat: this is combustion. Essentially, while the atoms of the fuel are rearranging into new molecules (such as carbon dioxide or water), they lose chemical energy and release it in large quantities as heat. That’s why, in the presence of air, a piece of dry wood heats up when it burns. This released heat then fuels the reaction, causing even more combustion, as long as there is fuel and oxygen available.
When the flame appears, it is due to combustion, a chemical reaction between a fuel (such as gas or wood) and the oxygen present in the air. This reaction breaks molecular bonds and forms other more stable ones; basically, it rearranges everything. When this happens, energy is released in the form of heat. All this heat causes an enormous rise in temperature, so high that some particles become incandescent. These white-hot particles then emit light through what is called incandescence, somewhat like bright red metal heated with a torch. But the flame also produces its light thanks to the presence of certain very excited chemical molecules and radicals (yes, excited!), which release energy as bright light when they return to their normal state. In short, your flame is the visible and burning result of a nice energetic chemical mess.
The typical shape of a flame primarily comes from gravity and convection. When air heats up, its density decreases and it becomes lighter, so it rises naturally. This ascent carries with it the hot gases from combustion, giving the flame its famous elongated and upward shape. The cooler surrounding air draws in and supplies the base with oxygen, thus maintaining a rather stable structure that is stretched and pointed upwards. Without gravity, the flame would be round, much more symmetrical and uniform.
The color of a flame is its identity card: it indicates at what temperature it burns and which chemical elements are consuming. A blue flame? It’s very hot, it can exceed 1500°C, often from well-oxygenated gas (like your stove). A yellow-orange flame is cooler (about 1000°C), a sign of incomplete combustion that forms glowing carbon particles: that’s the infamous soot. More specific flames, like green or red, appear when particular chemicals burn: copper for the green flame, certain strontium salts for the red one.
And the size? It mainly depends on the available oxygen and the amount of fuel. Lots of oxygen and little fuel produce a small and intense flame. In contrast, too much fuel compared to the available air produces a large, slow, and smokier flame. So when you see a huge orange flame that’s smoking a lot, tell yourself that it's probably missing a good bowl of oxygen over there!
In a weightless environment, flames do not take on their usual elongated shape, but instead become spherical due to the absence of gravity-related convection.
Although we generally associate it with intense heat, a typical candle flame does not exceed 1000°C, while some industrial flames fueled by acetylene can reach over 3000°C.
The specific colors of fireworks come from specific chemical compounds added to the combustion mixture. For example, copper produces blue or green shades, while strontium produces a bright red hue.
A wildfire can create its own local climate. By producing a massive column of hot air that rises rapidly, it draws in cooler air towards its base, creating powerful winds that can fuel its spread.
Exactly! A blue flame indicates a more complete combustion and a higher temperature (around 1500 °C), while a yellow or orange flame often signals a partial combustion at around 1000 °C, due to the presence of glowing soot.
Gently blowing feeds the fire by bringing in more fresh oxygen, thereby promoting combustion; however, blowing too hard cools the particles involved in the reaction and disperses the combustible gases, thus extinguishing the flame.
Sure, here’s a translation of your text: "Yes, but surprises guaranteed! In the absence of gravity, flames lose their usual elongated shape pointing upwards, taking on a spherical appearance due to equal diffusion in all directions without natural convection."
Some materials, when they accumulate enough heat through slow internal chemical reactions, can exceed their autoignition temperature and may then ignite spontaneously without any external flame source.
Neither one nor the other! Fire is actually a hot mixture of gases, vapors, and burning particles (the famous plasma), which is why it dances gracefully like a ghost heated to white-hot (much friendlier, of course!).
The hot air from the flame is less dense than the surrounding cold air, so it naturally rises, forming that characteristic shape pointing upwards due to the effect of Archimedes' buoyancy.
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