Combustion makes fireworks explode, matches catch fire, and candles burn. In this interactive, learn how a fire ignites, how chemical reactions rearrange the molecules of burning material, and what a flame is made of.
This feature originally appeared on the site for the NOVA program Fireworks!.
- Is there an opposite to absolute zero, the lowest possible temperature?
- In this flashy interactive, put on the pyrotechnician's hat and see a typical firework from the inside out.
- Explore what holds atoms together to form the myriad chemical substances found in our world.
- Travel from absolute zero to what may be the highest temperature of all.
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The Fire Lab and the Mysterious Science of Fire
How does fire spread? How do different forest materials fuel it? How can firefighters better understand its behavior in order to control it? Why is the physics of fire so counter-intuitive and mysterious to us?
At The Fire Lab in Missoula, Montana, highly-trained researchers conduct controlled tests with wind tunnels, fire-whirl generators, and giant combustion chambers to reverse-engineer fire.
High-speed camera technology records everything and allows them to analyze each detail.
Their mission: “improve the safety and effectiveness of fire management by creating and disseminating the basic fire science knowledge, tools, and applications for scientists and managers.”
The Mysterious Science of Fire by Katherine Wells and Sam Price-Waldman at The Atlantic, another great conversation starter about fire prevention and safety tips, and using matches as tools.
Related reading from May 2013: Archaeologists Find Earliest Evidence of Humans Cooking With Fire.
Related watching: What’s happening when a match is lit?, Why do hot things glow?, firefighter helmet cam, and Smokey and The Little Boy.
The Science of Fire
Given fire protection is the name of our game; we’re always interested in learning new facts about fire. These are not only interesting, but grow our knowledge on how to protect you better. So with winter on its way we thought, what better time to share this information with you!
Let’s talk about the science of FIRE.
Fire is a chemical reaction that releases light and heat. It is an event, not a thing and needs three components to exist; heat, oxygen and fuel. Fire is extinguished when one of these components is missing.
Heating wood or other fuel releases volatile vapours that rapidly combust with oxygen in the air. The resulting incandescent bloom of gas further heats the fuel, releasing more vapours and perpetuating the cycle.
Earth is the only known planet where fire can burn. No other planet has the required amount of oxygen to feed a fire. The air you breathe is 21 percent oxygen. The more oxygen there is, the hotter the fire.
Oxygen supply influences the colour of a flame. A low-oxygen fire contains lots of uncombusted fuel particles and will give off a yellow glow. A high-oxygen fire burns blue. So a candle flame is blue at the bottom because that’s where fresh air is taken up, and yellow at the top because the rising fumes from below partly suffocate the upper part of the flame.
The Science is Interesting, but What Does This Mean for You?
A fire can very easily tear through your home or workplace, which is why FireSafe exists; to protect your life and property. Fire is faster than generally thought and can take less than thirty seconds to become difficult to control.
This is compounded by the changes in furniture design and materials. Modern furnishings are frequently manufactured from cheap synthetic, hydro-carbon-based materials that burn and reach a very high temperature rapidly.
In earlier times, when natural materials, such as hardwoods were predominantly used, fires developed much more slowly.
“Flashover” occurs when the materials in a fire are heated to their ignition temperatures and catch fire.
If the bulk of materials are of similar type they will catch fire spontaneously and virtually simultaneously once the ignition temperature is reached. A relatively small fire can quickly develop into an inferno.
Hydro-carbon-based materials, once alight, emit large quantities of poisonous black smoke which is largely unburnt hydro-carbons.
These explode once ignition point is reached. The concentration of quantities of hydrocarbon-based materials in modern environments means that flashover point can be rapidly reached once a fire develops.
Additionally, the network of fire stations in the Sydney metropolitan area was built when flashover times were much longer. Fire stations were spaced out so as to be able to reach any building in their districts within the generally estimated time of flashover.
This is no longer the case; we would need fire stations on every corner to be able to do this now.
More people die from smoke inhalation than flames. Fire can suck all of the oxygen from a room and fill it with poisonous smoke and gases before flames even reach a room.
Assuming stable fuel, heat, and oxygen levels, a typical house fire will double in size every minute. Without a Fire Station next door, this lag time may result in the complete destruction of property.
The most common cause of fire deaths is cooking fires, with two of every five home fires started in the kitchen.
This is a very good reason to have a fire blanket and extinguisher in every kitchen, and ensure your smoke alarms are functioning correctly and checked regularly. FireSafe can assist with this.
Whilst all of this is alarming, FireSafe is here to help you decrease the risk of a fire starting in your home or workplace.
Fire blankets, extinguishers, smoke alarms and other such devices mitigate this risk. .
FireSafe prides itself on carrying the complete range of products and having the knowledge and know how to supply, install and maintain the fire protection products required for you.
For additional information and to discuss how FireSafe can help you, contact us today to speak to one of our friendly customer service representatives on 1300 347 372 or CLICK HERE
The Science Behind Fire
Posted by Dominic Cumberland, U.S. Forest Service, Office of Communication in Forestry Researchers prepare for the next phase in examining physical fire processes by adding the effect of a slope. Photo credit: Mark Finney
In recent months, we have all become familiar with images in the media of wildland firefighters digging lines, air tankers dropping retardant and fire engines dispersing water. You may wonder “how do these firefighters know what it takes to fight fire?”
The short answer is: research.
Before a wildland firefighter sees his or her first fire, they are given the tools and training on how to fight fire and its behavior. The information passed onto them is not learned overnight but rather through years of research.
In the US Forest Service’s Missoula Fire Sciences Laboratory, in Montana, employees conduct research on flame, smoke, fuel types and how fire spreads. The lab has six different focus areas including one called the Physical Fire Processes which studies the fundamental physics of fire spread.
Another one, Fuel Dynamics, works to make the process of fire behavior and its effects more accurately predictable, and the Smoke Emissions and Dispersion area’s focus is on a better understanding of smoke movement from fires and potential impacts.
Other focus areas concentrate on the effects of fire on plants and the study of how a forest responds to fire disturbances and climate change.
Fire and firefighting have been around for centuries, so what else can we learn? The answer is a lot. In fact, we learn more each day.
Why fires burn
We all know that if you gather up a bunch of dry twigs, grass and leaves and put a lit match to them, they’ll burn. Add some more sticks and bigger bits of wood and you’ve got a proper fire, ready for marshmallows. But how does fire actually work?
Fire is the result of applying enough heat to a fuel source, when you’ve got a whole lot of oxygen around. As the atoms in the fuel heat up, they begin to vibrate until they break free of the bonds holding them together and are released as volatile gases.
These gases react with oxygen in the surrounding atmosphere. This chemical reaction causes a lot of heat, so much heat, in fact, that it can keep driving the reaction—as long as there’s enough fuel and oxygen still present, the reaction will become self-sustaining.
The actual flames of the fire are the release of some of the heat energy as light.
These components have led to the development of the ‘fire triangle’ of fuel, oxygen and heat. Remove any one of these and fire cannot sustain itself.
The three essential components of fire. Take away any one 'side' and the fire will go out.
Why does water put out fire?
The primary role water plays in putting out a bushfire is cooling it down so there’s no longer enough heat to sustain the fire.
When you pour water onto a fire, the heat of the fire causes the water to heat up and turn into steam.
This is a very energy-intensive reaction, and it sucks away the heat (which is a form of energy) of the fire. This leaves the fire without enough energy to keep burning.
Less significant is the role water can play in ‘smothering’ a fire, depriving it of the oxygen that it also needs to burn.
This article was adapted from Academy website content reviewed by the following experts: Dr Rachel Nolan School of Life Sciences, University of Technology Sydney; Dr Richard Thornton CEO, Bushfire and Natural Hazards CRC; Dr Hamish Clarke School of Biological Sciences, University of Wollongong
Explainer: How and why fires burn | Science News for Students
According to Greek mythology, the gods took fire away from people. Then a hero named Prometheus stole it back. As punishment, the gods chained the thief to a rock, where an eagle fed on his liver.
Every night, his liver grew back. And each day, the eagle returned. Like other myths, the Prometheus story offered one explanation for the origins of fire. It doesn’t, however, offer clues to why things burn.
That’s what science is for.
Some ancient Greeks believed that fire was a basic element of the universe — one that gave rise to other elements, like earth, water and air. (Aether, that stuff the ancients thought stars were made of, was later added to the list of elements by the philosopher Aristotle.)
Now scientists use the word “element” to describe the most basic types of matter. Fire does not qualify.
A fire’s colorful flame results from a chemical reaction known as combustion. During combustion, atoms rearrange themselves irreversibly. In other words, when something burns, there’s no un-burning it.
Fire also is a glowing reminder of the oxygen that pervades our world. Any flame requires three ingredients: oxygen, fuel and heat. Lacking even one, a fire won’t burn. As an ingredient of air, oxygen is usually the easiest to find. (On planets such as Venus and Mars, with atmospheres containing far less oxygen, fires would be hard to start.) Oxygen’s role is to combine with the fuel.
Any number of sources may supply heat. When lighting a match, friction between the match’s head and the surface against which it’s struck releases enough heat to ignite the coated head. In the Avalanche Fire, lightning delivered the heat.
Fuel is what burns. Almost anything can burn, but some fuels have a far higher flash point — the temperature at which they’ll ignite — than others.
People feel heat as warmth on the skin. Not atoms. The building blocks of all materials, atoms just get antsy as they warm. They initially vibrate. Then, as they warm even more, they start dancing, faster and faster. Apply enough heat, and atoms will break the bonds linking them together.
Wood, for example, contains molecules made from bound atoms of carbon, hydrogen and oxygen (and smaller amounts of other elements). When wood gets hot enough — such as when lightning hits or a log is tossed on an already burning fire — those bonds break. The process, called pyrolysis, releases atoms and energy.
Unbound atoms form a hot gas, mingling with oxygen atoms in the air. This glowing gas — and not the fuel itself — produces the spooky blue light that appears at the base of a flame.
But the atoms don’t stay single long: They quickly bond with oxygen in the air in a process called oxidation. When carbon bonds with oxygen, it produces carbon dioxide — a colorless gas. When hydrogen bonds with oxygen, it produces water vapor — even as the wood burns.
Fires burn only when all that atomic shuffling releases enough energy to keep the oxidation going in a sustained chain reaction. More atoms released from the fuel combine with nearby oxygen. That releases more energy, which releases more atoms. This heats the oxygen — and so on.
The orange and yellow colors in a flame appear when extra, free-floating carbon atoms get hot and begin to glow. (These carbon atoms also make up the thick black soot that forms on grilled burgers or the bottom of a pot heated over a fire.)
The science of fire • Techniquest
Photo by Jacob Kiesow on Unsplash
It’s getting hot in here with our Fire and Light show taking over our Science Theatre this half term, and our fiery show will see our science communicators set money on fire, play with the colour of flames, and even set light to a fire tornado. Don’t worry, the Health and Safety is all in place and no one’s leaving with singed eyebrows.
As we study the fire triangle and perform exhilarating experiments this half term, we’ve decided to dig into the science of fire. More specifically, we answer one burning question- what makes fire change colour?
The colours of flames come from two things…
While colour can depend on temperature, chemical reactions often take most of the credit. A fire itself is the result of a chemical reaction known as combustion, where fuel and oxygen react with one another and atoms rearrange themselves irreversibly.
For this to occur, fuel must reach its ignition temperature, and combustion will continue if there is enough fuel, heat and oxygen.
Once the temperature gets hot enough for the chemicals in the fuel to react with oxygen, it results in a colourful reaction. Red colours are the coolest flames, while lighter colours represent scorching temperatures.
In wood fires, the colours also come from the substances burning within the flames. The fierce orange flame is due to the presence of sodium, which emits once heated, copper compounds transform into green or blue, and lithium turns into red.
Why does fire burn blue sometimes?
The colour of flames is not limited to the glows of warm reds and oranges, and most of us have probably seen a blue flame.
The colour of a flame is influenced by oxygen supply, meaning that low-oxygen fires contain uncombusted fuel particles, leading to yellow glows. High-oxygen fires burn blue, and its flames are the hottest, defeated only by the heat of a white flame.
As with other colours, blue is a direct consequence of a chemical reaction, with carbon and hydrogen producing both blue and violet flames.
If you’re coming to visit us with the little ones over half term, don’t forget to pop in to the Science Theatre! For times and to book your tickets to Fire and Light, please see here.
How Fire Works
Typically, fire comes from a chemical reaction between oxygen in the atmosphere and some sort of fuel (wood or gasoline, for example). Of course, wood and gasoline don't spontaneously catch on fire just because they're surrounded by oxygen. For the combustion reaction to happen, you have to heat the fuel to its ignition temperature.
Here's the sequence of events in a typical wood fire:
Something heats the wood to a very high temperature. The heat can come from lots of different things — a match, focused light, friction, lightning, something else that is already burning…
When the wood reaches about 300 degrees Fahrenheit (150 degrees Celsius), the heat decomposes some of the cellulose material that makes up the wood.
Some of the decomposed material is released as volatile gases. We know these gases as smoke. Smoke is compounds of hydrogen, carbon and oxygen.
The rest of the material forms char, which is nearly pure carbon, and ash, which is all of the unburnable minerals in the wood (calcium, potassium, and so on). The char is what you buy when you buy charcoal.
Charcoal is wood that has been heated to remove nearly all of the volatile gases and leave behind the carbon. That is why a charcoal fire burns with no smoke.
The actual burning of wood then happens in two separate reactions:
- When the volatile gases are hot enough (about 500 degrees F (260 degrees C) for wood), the compound molecules break apart, and the atoms recombine with the oxygen to form water, carbon dioxide and other products. In other words, they burn.
- The carbon in the char combines with oxygen as well, and this is a much slower reaction. That is why charcoal in a BBQ can stay hot for a long time.
A side effect of these chemical reactions is a lot of heat. The fact that the chemical reactions in a fire generate a lot of new heat is what sustains the fire. Many fuels burn in one step.
Gasoline is a good example. Heat vaporizes gasoline and it all burns as a volatile gas. There is no char. Humans have also learned how to meter out the fuel and control a fire.
A candle is a tool for slowly vaporizing and burning wax.
As they heat up, the rising carbon atoms (as well as atoms of other material) emit light. This “heat produces light” effect is called incandescence, and it is the same kind of thing that creates light in a light bulb. It is what causes the visible flame.
Flame color varies depending on what you're burning and how hot it is. Color variation within in a flame is caused by uneven temperature. Typically, the hottest part of a flame — the base — glows blue, and the cooler parts at the top glow orange or yellow.
In addition to emitting light, the rising carbon particles may collect on surrounding surfaces as soot.
The dangerous thing about the chemical reactions in fire is the fact that they are self-perpetuating. The heat of the flame itself keeps the fuel at the ignition temperature, so it continues to burn as long as there is fuel and oxygen around it. The flame heats any surrounding fuel so it releases gases as well. When the flame ignites the gases, the fire spreads.
On Earth, gravity determines how the flame burns. All the hot gases in the flame are much hotter (and less dense) than the surrounding air, so they move upward toward lower pressure.
This is why fire typically spreads upward, and it's also why flames are always “pointed” at the top.
If you were to light a fire in a microgravity environment, say onboard the space shuttle, it would form a sphere!
Lesson 2 – Fire Science and the Fire Triangle – Country Fire Authority
NOTE: This lesson may not be suitable for level 0-1 students.
For students to understand the fire triangle; the three things a fire needs to burn.
The Fire Triangle (developed for the Fired Up English resource)
Fire needs three things to burn:
- Heat, which could be from lightning, the sun, or radiant heat from a heater
- Fuel, which could include wood, paper, leaves, gas or petrol
- Oxygen (air)
Fire is the chemical reaction that occurs when these three things are present and the conditions are right. Removing any one of these three things can cause the fire to go out.
- If you add water, this takes away the heat and can cause the fire to go out.
- If you smother the fire with a fire blanket, you take the oxygen away and can cause the fire to go out.
- If you rake the leaves and grass away until there is only dirt, you remove the fuel and can cause the fire to go out.