Things to know about the Fire - The difference between people and things

Have you ever wondered how fire was born? How does fire look like? What is the nature of the fire .?

Fire can destroy your home and all you have in less than an hour, turning a vast forest with only coal and ash. Fire is also a terrifying weapon, with almost limitless destructive power, every year fire takes more lives than any other natural power.

On the contrary, fire has many uses in life. Fire gives us light and warmth. Fire also helps to cook food, forge metal, make ceramics, burn bricks, and operate thermal power plants . In short, fire is a dangerous thing, but also an integral part of life. . It is really one of the most important elements of human history.

So, exactly, what is fire?

Ancient Greeks believed that fire was one of the main elements of the universe, besides water, earth and air. You can feel the fire, like you can feel the earth, water and gas. You can also see, smell fire, and you can bring fire anywhere.

But in fact, fire is something very different. Earth, water and gas are composed of billions of atoms, and always remain the same. Fire is not like that: fire can turn to other forms - it is part of chemical reactions.

What is fire?

Normally, fire comes from a chemical reaction between air oxygen and some kind of fuel (wood, kerosene, .). Of course, wood and kerosene in the air will not be able to burn itself. In order for a fire reaction to occur, we need to heat the fuel to their burning temperature - ignition temperature.

First, we will talk about the process of burning a substance. For example, when burning a log, the process happens as follows:

- The wood is getting hotter. Heat sources can be anything: matches, focusing sunlight, rubbing, something burning .

- When the log reaches a temperature of about 300 degrees F (150 degrees C), the heat will decompose some cellulose components of that log.

- The separated components of that log, which will form volatile gas, is smoke. This smoke includes hydrogen, carbon and oxygen. At that time, the log left only charcoal - almost pure carbon, and ash - contains unburnable minerals (such as calcium, potassium .). Charcoal is the wood that has been heated to the point where it loses all the gases inside and only carbon remains. And so, there will be no smoke generated when you burn charcoal.

In fact, when burning a log, there are two separate processes.

- When the gas is produced hot enough (about 500 degrees Fahrenheit, 260 degrees Celsius), the bonds in the molecule break down into smaller atoms, and they combine with air oxygen to produce water and CO2. and other products.

- Carbon in charcoal will also react with oxygen, but this reaction is slower. Therefore, when you grill something with charcoal, you will find them very hot for a long time.

These reactions will occur when they occur. The chain of reactions occurs continuously, the amount of heat generated is enough to maintain the flame. The reaction process is true when we burn a log, but for many other fuels the process takes only one step. Gasoline is an example. The heat will turn on the gas vapors and then burn them, coal is not produced like when burning wood. Humans have learned how to adjust the fuel to be used and adjust the flame to suit the purpose of use. The main candle is a form that shows the slow and burning evaporation of wax.

When heated, carbon atoms (and other elements) emit light.This 'light-producing' heat is called incandescence , which is essentially the same as the incandescent light bulb. And it is this phenomenon that will show the fire. The color of the fire varies, depending on what is burning and how hot it is. When you see a colorful fire, such as looking at the flame of a gas stove, you will see that it has many different colors, which is due to the temperature difference. Normally, the hottest place of the fire - at the bottom - is blue, while the lowest temperature is yellow and orange.

In addition, carbon atoms can leave black streaks around when the fire burns, which is the soot or soot, which we often see at the bottom of pots when cooking with a charcoal stove.

The most dangerous thing here is, chemical reactions that have a fire happen, they have a long-lived self-perpetuating nature. The heat from the fire can keep the fuel at a burning temperature, and they will burn until the fuel runs out or the oxygen around. The fire burns the surrounding fuel to evaporate, when the flames catch fire they will burn, and the fire spreads everywhere.

On Earth, gravity determines the nature of the fire. Hotter air streams will have a smaller specific gravity, and they will float upward towards lower pressure. That is why you observe the fire often 'sharp' at the top. If you group a fire in a zero gravity environment, such as in a spaceship, you will see a spherical flame!

The diversity of the fire

In the previous section, we saw, fire is the result of a chemical reaction between two gases, typically oxygen and gas. Gas generated by heat. In other words, when the initial thermal energy is supplied, the bonds in the gas molecule are broken, the atoms released will react with oxygen in the air and thereby produce another compound along with the amount bigger heat.

In fact, only some compounds are broken and react in the same way, atoms must be attracted to each other in some way. If you try with water, for example, when you boil water, hot water will turn into steam, flying up to meet oxygen but no reaction will occur. This is because the hydrogen atoms and oxygen in the water and the oxygen atom of the air are not attractive enough to produce a reaction, so the water molecule is not broken and the reaction does not occur.

The most flammable compounds, which are compounds that contain carbon and hydrogen, are easily combined with oxygen in the air to create CO2, water and other gases.

Different combustibles will ignite and burn at different temperatures. They need a certain amount of heat to be able to transfer substances from their original form to vapor, and add more heat to start reacting with oxygen. The amount of heat needed depends on the nature of the molecule that makes up the fuel. It is often divided into two temperature ranges: a piloted ignition temperature , which is the temperature required to turn fuel into a gas that can burn when exposed to electric sparks. And the second level , unpiloted ignition temperature , is much higher than level one, at this temperature, the fuel will immediately burn without the need for sparks.

The size of the fuel also affects how quickly they burn. A large tree trunk will be able to absorb more heat, will need greater heat to burn them. Conversely, a piece of wood the size of matchsticks will burn easily because they are heated up very quickly.

The amount of heat generated by burning fuels also depends heavily on the amount of energy they release and their rate of combustion. Both of these factors depend heavily on the structure of the fuel. Some compounds react with oxygen very quickly and strongly, giving off a large amount of heat. For some other types, only a small amount of heat is released. Similarly, the reaction rate of fuel with oxygen can be fast or slow, as in the example of charcoal above.

The shape of the type of fuel also affects the rate of combustion. Thin pieces will burn faster than large pieces due to their contact area with larger oxygen. For example, a flat piece of wood, or a piece of paper, will burn faster than a block of wood of the same weight, because the piece of wood and paper have larger areas of contact with the air.

And from there, you can see, fire from different fuels, like different animals, they have different characteristics. Based on that, experts can determine how the fire originates when observing them and how they affect the surrounding environment. Flames from combustible fuels will do more harm than slow-burning and low-heat fuels.