Tag Archives: Fire

Microwave Plasma

We go through our daily lives encountering three of the states of matter; solid, liquid, and gas; nearly every moment, but the fourth, plasma, is much rarer for most of us. Plasma can be found around most forms of visible electricity, like lightning, but you can find it inside your microwave if you follow the steps below. Before you get started, however, this experiment MUST be carried out with immense care and with an adult present; it is very easy to get this experiment wrong and deal damage to not only your microwave, but yourself as well.

For this experiment, you’ll need a microwave, a toothpick, a microwave-safe glass container, three discs of cork (or any material you can stick a toothpick into and use to prop up the glass, and a match. Place the four discs of cork in the microwave so that one is in the center and the other three are around it far enough for the glass container can rest on top of them. This is essential, as air needs to flow between the inside of the glass container and the inside of the microwave. Stick the toothpick into the center cork disc, and set the microwave to 20 seconds, but don’t run it yet.

microwave plasma

Light the toothpick and cover with the glass container, closing the door of the microwave and hitting start. You should see arcs of plasma coming from the lit toothpick and while it’s tempting to leave it go and watch for a while, only let it run for a few seconds. Otherwise, the glass will get too hot and could shatter, spreading broken glass through your microwave and removing the housing for the plasma, potentially lighting your microwave on fire. After you’ve shut off your microwave, let it sit closed for about a minute, allowing the glass to cool down, otherwise the sudden inrush of cool air from the outside could shatter the still hot glass.

microwave plasma 1

Those plasma arcs were cool, but how exactly did we make them? Well, plasma is essentially ionized gas, requiring either an increase in heat or adding more electromagnetic force, both of which are happening inside the microwave. When an object is burned, the fire is actually stripping away electrons, ionizing the atoms around the fire until the electrons get recaptured. Microwaves work by establishing a standing wave of electromagnetic fields, which push and pull the electrons stripped away from the fire. This causes them to collide with the air molecules inside the glass, adding heat to the air and stripping away more electrons. This continues until the air is ionized to the point of becoming plasma, dissipating, and then ionizing into plasma again. The reason we can actually see the plasma also comes down to those electrons, as their collisions with the air molecules can add energy to the air’s electrons, which then fall back into their normal energy levels and release light, similar to the effect of fluorescence we’ve mentioned in previous pieces.

If you want to make plasma yourself, get an adult and try it, but please remember to be careful.

An Egg and Fire

This experiment is very easy to do but will blow your mind. We have said time and time again that light can bend and reflect in crazy ways. Here is another example of that.

Just by charring the outside of a raw (or cooked) egg shell and dipping it in water, you will be able to see something crazy! The egg appears to turn silver. But when you lift it up out of the water again it goes back to black?

Egg

The carbon soot that builds up in the outside of the egg is a combination of multiple sized particles of carbon. Those particles trap air along the surface.

Eff

This air layer traps light that is traveling through the glass, water, and air, and causes total internal reflection to occur. Total internal reflection is when light enters a medium and is reflected back and forth at the boundary of the medium, in this case the water and air boundary.

Behind the Scenes with a Lighter Flame Float

It’s a classic trick to make a lighter flame float, but how does it actually work? As it turns out, the secret can be found on your desk: a ballpoint pen. Though the key to the trick may be simple, there’s some really cool science making it happen. Follow along with us and we’ll show you how and why this works. Be careful though, you will be handling fire.

Lighter pen

The first thing you need to do for this is take apart your pen, leaving nothing but the tube of ink behind. When doing this, it’s a good idea to have a paper towel down to catch any ink that leaks out of the tube.

Lighter ink

Then, collect some ink with an unfolded paper clip and cover the nozzle inside the lighter where the fuel comes out. This ensures the fuel and ink will mix, a vital part of the experiment. This was the most direct means of mixing the ink and fuel for our disposable lighter, but other lighters have more direct means of accessing the fuel reservoir and those should be taken first.

Lighter flame

Once you’ve mixed the ink and the fuel, your flame should appear to float over the lighter. Depending on how well the ink and fuel mix, this effect could be brief, so watch carefully. We know how we get it to float now, but why does adding ink to the lighter fuel make it float?

Normally, butane lighter fuel releases blue light when burned, but the addition of the ink pushes that energy release into the ultraviolet part of the spectrum. Since our eyes can’t see UV light, the portion of the flame from the burning ink appears invisible, producing the illusion that the rest of the flame is floating.

Fireproof Balloons

If you’ve ever brought a match to a balloon (or been in our Atmosphere and Gases class), you know that fire and balloons don’t mix, but what if you could prevent a balloon from popping when it comes in contact with fire? The answer to this dilemma can be found in the simplest place: water. A little bit of water in a balloon that is otherwise filled with air can prevent it from popping when burned. To understand why, let’s take a look at what’s happening during a balloon and match collision.

With an ordinary air balloon, the flame heats up the skin of the balloon until it weakens, popping the balloon, but when that match is held against the water-filled part of a balloon, the skin doesn’t weaken or pop.

This experiment is all down to the difference in heat conductivity of water and air. Air is unable to conduct heat away from the skin of the balloon fast enough to keep it cool, resulting in a popped balloon. However, water conducts heat away much more effectively, cooling down the rubber and preventing it from breaking. Throughout this process, the hot water rises to the top, allowing the cool water to take its place, absorb heat, rise and continue in a cyclical current. Water also requires much more heat energy put into it before warming up than air, allowing it to maintain this current longer.

This current only exists so long as you heat the balloon from the bottom, and if you place the match on the side or air-filled section, the balloon pops normally. When doing this experiment, you may notice a black smudge where you placed the match, but this isn’t a burn mark; it’s actually just carbon deposited on the balloon from the burning match.

If this looks like fun, grab some balloons, a heat source, some water and an adult, and try it today!

What’s the Matter: Is Fire a Plasma?

Is fire a plasma? Turns out it’s not a trivial question! The answer depends on how you define the parameters of the fourth state of matter. Descriptions of plasma commonly include the following points: plasma is what happens when a gas is subjected to lots of ionizing energy. Although thoroughly ionized, it is quasi-neutral. Its molecules display collective dynamics and respond as a group to electromagnetic influence.

suniris

The sun as seen by NASA’s IRIS orbiter. Ultraviolet image translated into false color for human consumption. Stars, including our sun, are made of plasma.

Most of the observable universe is made up of plasma! Astrophysical plasmas are mind-blowingly hot. On Earth, too, plasma is created by copiously applying heat or otherwise energizing a gas, although plasmas can also be created in laboratory scenarios that are cold by human standards.

So, which state of matter does fire belong to? Depending on who you ask, a flame is either a low-level plasma or a lightly ionized gas. A flame is a heated volume of air in which some electrons have broken free from their nuclei, but it’s not hot enough (or ionized completely enough) to enable cohesive electrodynamic behavior on the level of, say, an arc welder.

 

Plasma or not, the gas within a flame contains enough ions to make it a decent electrical conductor! Here, electricity arcs from a generator to a candle flame.

Fire Tornado!

Tornadoes are born when extreme weather circumstances come together. Their short, destructive lives are still not fully understood, but one leading theory goes like this: sometimes, winds at different altitudes blow at different speeds, rolling the air between them into a horizontal, rotating cylinder. If a supercell thunderstorm is nearby, the spinning column can be pulled into the maelstrom. Once the tornado is vertical, its lower end has the potential to touch down and wreak havoc on Earth’s surface.

West Texas wildfire

West Texas wildfire. Image credit: Texas Forest Service.

In a real supercell, swirling updrafts are created by variations in temperature, pressure, and wind speed in the storm area. In this experiment, we simulate updraft conditions by physically pushing the air into a rotating column formation using a window screen rolled into an open-ended cylinder. Without the screen (and the wind it generates), the spinning fire doesn’t do anything especially interesting. That’s because of Bernoulli’s principle: the faster a volume of fluid moves, the more neighboring molecules are sucked into the breeze. By giving the air a push, we draw extra oxygen in towards the flame.

FireTornadoGif

Fire tornadoes are spectacular in the lab, but you don’t want to see one in nature. These twisting ropes of flame have played a tragic role in several of the greatest conflagrations in human history. From Chicago to Peshtigo to Tokyo and beyond, they’ve spread blazes with devastating speed and blocked victims from reaching safety in nearby bodies of water.

At least one team of researchers is working towards harnessing the power of the fire whirl for practical purposes. Hot, clean-burning blue fire tornadoes show potential as a tool for improved oil spill cleanup.

As with any experiment involving combustion, check in with an adult, keep a fire extinguisher on hand, and exercise caution if you decide to make a flaming tornado at home. We used a turntable with a heat-safe covering, a non-flammable window screen stapled into a cylinder, duct tape, a glass flask, and a few ounces of 99% isopropyl alcohol to create our fire whirl.

Written By: Caela Barry

DIY Fireproof Cash

smallmoneyburnWe soaked this $5 bill in flammable rubbing alcohol and then lit it on fire. So how did it survive? Does it have something to do with the bill itself?

This demonstration is impressive with money, but we haven’t been able to find an example of it using other materials. Many people have asked us what would happen to regular paper in the same situation. This opened up the chance for us to do some real science! We repeated our experiment, replacing the dollar bill with standard white paper and a brown paper napkin. Neither of these caught fire either.

The key to this trick is the part that stayed the same in all three experiments: a solution of rubbing alcohol and water. Water has a high specific heat, so changing its temperature takes a lot of energy, as we’ve seen before. Unlike water, rubbing alcohol is very flammable. It easily burns away until most if it is gone, leaving behind a mixture consisting primarily of water.  

By lighting pools of alcohol on our fireproof table tops, we measured the temperature of the water left behind after burning off as much of the alcohol as we could. Here are the results:

comparison

smallpaperDespite being literally covered in fire for thirty seconds, the water temperature only climbed by 11.8 degrees Fahrenheit! The water in the rubbing alcohol mixture is protecting the money with its high specific heat, preventing the paper in all of the above examples from getting hot enough to burn. As such, when performing this experiment, it’s very important that we completely soak the money (or other experiment subject). If any surface is exposed, it will catch on fire! After the flame has gone out, the paper doesn’t even feel warm to the touch.

Only try this at home with adult permission and a fire extinguisher!

Written by: Scott Alton

 

The (Almost) Invisible Fuse

When you light a candle, wax melts and travels up the wick via capillary action. As it gets close enough to the heat source, the wax vaporizes and ignites, providing more heat, which melts more wax, which is wicked up into the flame in turn. The cycle continues until fuel runs out, oxygen is depleted, or the heat source is removed (i.e. the candle is blown out).

In general, solid and liquid fuels burn when heat exposure causes them to release flammable vapors. Byproducts of gaseous combustion float away as smoke.

CandleSmokeGif

Extinguish a candle, and some wax vapor is left over in the smoke trail. In the moment before it dissipates, this column of flammable gas can act as a fuse and carry a flame back down to the candle wick.

This experiment depends on Earth’s gravity to work. Here on our home planet, the behavior of fire is predictably familiar. Warm air around the flame rises. Cool air rushes in to fill the void at its base, carrying a fresh supply of oxygen. The combustion reaction continues, heating more air and propagating the convection cycle.

Flex2

Image credit: NASA/FLEX-2

Without Earth’s gravity to pull cool, dense air downward, hot air doesn’t float. For this reason, flames in space burn spherically, and a smoke trail would never rise from an extinguished fire!

Written By: Caela Barry

Survival Skills: Science Style

Light travels incredibly fast. In a vacuum, it speeds along at nearly six trillion miles per hour. Ever notice how your feet look distorted when you wade in the water, or how a straw seems to be cut in half where it enters a full glass? When light travels through a medium, it slows down. When a collection of light rays crosses from one material to another (from water into air, for instance), the change in speed warps the image.

StrawSmall

This warping effect can appear random, as in the case of rippling water, or it can be well-organized. We often take advantage of light’s transition between air and glass, for example, to bend images in a useful way. A magnifying glass works by taking a small image and spreading it out over a large area. What happens when you use it backwards– put a large cross-section of light in, then focus it down to a tiny point?

SunBurn

Try this with the sun as a light source on a warm day, and you’ll find that the visible light and heat at the focus point are intense enough to burn wood!

Written By: Caela Barry

Why on Earth Can Oranges Spray Fire!?

Oranges are fruits that grow on trees. They are made up of almost 90% water by weight. This should pretty clearly mean that they are not flammable. However, there is something going on. Take a look:

Orange fire montage big cropped

Inside of the peel is a special oil called D-Limonene that is quite flammable. What reason could an orange have for harboring a fiery fluid in its skin? Well, it has to do with where baby oranges come from.

orange_PNG806That’s actually a tad misleading. Oranges contain the seeds of orange trees. The orange itself is another orange tree ready to grow, but the original tree doesn’t want to get too crowded. This orange needs to go off and grow somewhere else. To do that, it simply has to be delicious. If the orange is eaten and then pooped out elsewhere, it can grow into a nice successful orange tree and produce oranges of its own. The problem, of course, is that oranges are too tasty!

It’s not just the desired animals that will nicely eat the oranges and carry their seeds to a new home, it’s also pests like bugs, which are… less qualified for this important task. As a defense, oranges contain the previously mentioned D-limonene, which drives away insects and mold. This makes the orange more likely to be devoured by its target audience, which leads to more orange trees and then to more oranges!

K-Mega Farms

Interesting side note: most oranges in grocery stores are seedless! In fact, the one in the video is seedless. Instead they are grown through a bizarre process called grafting, where a piece of seedless orange plant is stuck to another and they grow together. Image from K-Mega Farms.

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