Tag Archives: Fire

Colored Fire for a Happy Halloween!

Note: This involves combining fire which can always be dangerous with chemicals that can irritate skin or badly hurt eyes! Only do this with proper supervision and safety equipment including goggles, gloves, and a fire extinguisher!

The classic Jack-o-lantern has been around for hundreds of years. The tradition was brought to America by the Irish, who had originally started carving the spooky faces into turnips based on a folk tale. Moving to pumpkins was undoubtedly an upgrade, and we think it’s about time for another one!

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The lighting of a jack-o-lantern is classically done by candles. Candles burn with a yellowish flame giving off a special glow, but there are ways to make flame in different colors! To do this, the fuel simply needs to have different kinds of salts added. When you think of salt, it probably conjures images of a table seasoning known as sodium chloride, but this is not the only possibility.

Salt actually a scientific term referring to the category of molecule that is left over from pouring acidic and basic solutions together. Fortunately, to acquire these salts, you don’t need to risk working with potentially dangerous acids that could leave you with a costume you couldn’t take off!

Most of these are the result of mixing something with hydrochloric acid, which means that they are often chlorine combined with another molecule, just like sodium chloride! Adding energy in the form of fire causes these molecules to give off unique energy in the form of differently colored light!

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Caption: Different salts give off different colors of light. This can come in many forms including from red strontium chloride and green from cupric chloride.

jackolantern-colorOur fire source was rubbing alcohol, with the chosen salt stirred in. To keep it from going everywhere, we used a small glass jar instead of the dishes above. To make sure the liquid burned easily and evenly, we used a cotton ball as a wick like a candle, and put it in the jack-o-lantern!.

CO2 Fire Extinguisher

“Fire… begone!” These words aren’t magic, they’re science! We’ve harnessed the unique properties of a certain gas, carbon dioxide, to make our own version of a fire extinguisher. To understand how this works, we need to start with an understanding of fire. Fire requires two things in order to continue burning: fuel and oxygen. Without those fire will cease to exist. Our homemade fire extinguisher deprives fire of the second ingredient: oxygen.

We start with some dry ice. Dry ice is simply the solid form of carbon dioxide. When the dry ice heats up, it sublimates and turns into its gaseous form. Carbon Dioxide in its gas form is invisible and very dense. It’s density allows you to scoop it in a pitcher the same as you would a liquid, except that you can’t see it. When poured out it is heavy enough to push away all of the oxygen around the fire. No oxygen, no fire! Tada!

A Scientist’s April Fools


Warning: Don’t do this at home!  When a scientist decides to play an April Fools prank on someone, it gets pretty serious.  We pull out all the stops.  One experiment that is guaranteed to both terrify and delight is the classic alcohol money burn.

The experiment is pretty simple.  Mix some rubbing alcohol and water until your solution is about 50% alcohol.  Take a bill (we would recommend a small one in case something goes bad) and dip it into the alcohol.  Get any excess liquid off of the bill so that it isn’t dripping,  Light it on fire!

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Whoa!

The amazing thing about this experiment is that the money doesn’t actually burn.  The fire goes out after a few seconds and the bill is unharmed.  April Fools!  But why?  The secret lies in the water.  The water mixed in with the alcohol is what is absorbing the heat of the fire, not the money.  If the bill was soaked in pure alcohol it would be roasted in seconds.  But water has a really good specific heat, meaning it takes a lot of energy to heat it up.  The alcohol doesn’t burn hot enough to overcome this specific heat,  and as a result the money stays safe.

Fire & the History of Matches


NOTE: DO NOT TRY THIS AT HOME!

Humans have been creating and controlling fire for almost a million years! Our early ancestors used friction – essentially rubbing sticks together – to create their first fires for cooking food and making tools. Today we can carry fire making tools around in our pockets.  Every year 500 billion matches are used in the United States alone. Even though we’ve come a long way from rubbing sticks together, matches today work on a very similar principle – friction. For an example of this, you can try rubbing your hands together. You should feel them get warm. It should not start a fire.

Match bodies are made of wood or stiff paper, to provide fuel for the fire. Match heads are coated in phosphorous based compounds that catch fire when heated up. The heat that lights a match generally comes from friction when you rub or “strike” a match on a rough surface. Early “strike anywhere” matches were coated in white phosphorous, but the white phosphorus was too easy to light. This made them rather dangerous, as they tended to ignite accidentally. Great if you needed to light a fire in a hurry…but not so great if you need to ship them long distances, or keep them for a long time.

Match

To get a combustion reaction like this to start requires something in chemistry called “activation energy”. This simply refers the amount of energy needed to start the reaction. These matches lit so easily because the white phosphorous in the match head needed very little energy to light. Simply rocking around in a crate could cause enough friction to ignite them. Today’s strike anywhere matches use a less dangerous form of phosphorous (phosphorous sesquisulfide). They can still be lit on any surface rough enough to create the right amount of heat from friction, but anyone who has tried (and failed) to light a match multiple times can tell you it takes a bit more effort.

In the video, the bright parts you see as the fire moves along consuming all of the matches is this phosphorus beginning to ignite. It doesn’t last very long, and its job is just to keep the match burning long enough for it to get hot and start burning the wood, which is what sustains most of the flame that you see in the end!

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