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  • THE CHEMISTRY

  • OF FIREWORKS

  • I’m John Conkling,

  • I'm an adjunct professor of chemistry at

  • Washington College in Chestertown Maryland.

  • I wrote a textbook, "The Chemistry of Pyrotechnics: Basic Principles and Theory."

  • Everything you see in a fireworks

  • display is chemistry in action.

  • How the colors are all produced by very

  • specific chemical mixtures that produce

  • beautiful color flames.

  • The sparks are small pieces of fuel

  • that continue to burn in air.

  • Without chemistry, you couldn't

  • have the burning mixtures.

  • Without the burning mixtures,

  • we wouldn’t have the fireworks.

  • LETS TALK CHEMICALS

  • Every pyrotechnic composition has at least

  • one chemical that's oxygen-rich an oxidizer:

  • Potassium nitrate used to make black powder.

  • Potassium perchlorate used in

  • a lot of color compositions.

  • Strontium nitrate is an oxygen-rich chemical,

  • but the strontium being in there

  • also produces a red flame color.

  • Then you need a fuel that's gonna combined

  • with the oxidizer to produce heat.

  • The fuels are things like sulfur, charcoal,

  • aluminum powder, magnesium powder, you vary

  • your fuel to get a specific heat output.

  • Specific burning rate to try and get

  • the exact behavior you looking for

  • in your chemical reaction.

  • Most people when they think a fireworks

  • think of the skyEXPLODING!

  • AERIAL SHELLS

  • This is an aerial shell, this is what people

  • go to watch a fireworks display at sea.

  • It's a cardboard casing.

  • The bottom has a little pocket of black powder,

  • granular black powder propellant.

  • There's a very important time fuse that goes

  • from the propellant into the center of the casing.

  • That determines when the shells

  • going to burst up in the air.

  • The inside of the sphere itself has

  • a black powder bursting charge,

  • and then a number of little green pea

  • marble sized pellets of chemical mixture,

  • that will produce different colors different

  • visual effects when the shell burst open.

  • So this device is placed in a mortar tube,

  • a fuse or it's gonna be electrically fired

  • a wire and extends out into mortar tube.

  • At exact time you wanna fire it,

  • the signals is given, the button’s

  • pushed the propellant ignites and

  • throws this device up into the air.

  • At the same time this little delay fuse,

  • which is running from the propellant up

  • into the center the shells burning.

  • And then 3,4,5 seconds later, depending on how

  • high you wanted to go burns into the center in

  • the shell, light that gunpowder bursting charge,

  • and - BOOM! - blows the shell open up

  • in the sky and you see the beautiful colors,

  • the sparks, all the effects, the patterns

  • that have been engineered into the device.

  • We produce colors by using the fact

  • that different chemical elements,

  • heated to high temperature,

  • get rid of this energy by emitting

  • very specific wavelengths of light.

  • You know this is the stock room where

  • we keep a broad assortment of chemicals.

  • Copper oxide is a chemical element

  • that will produce a very, very

  • nice blue flame color for us.

  • For a red you’d look for a strontium

  • compound, here’s strontium chloride.

  • Sodium of course will produce

  • the yellow orange, sodium silicate.

  • Calcium makes a nice yellow orange here’s

  • a calcium nitrate or the calcium carbonate.

  • If we want a grain color we need some kind

  • of a barium compound, this is barium acetate.

  • You look for chemicals that don't strongly

  • pick up water, that are not hygroscopic.

  • SAFTEY FIRST!

  • Anytime we have students in the lab

  • or I'm doing demos, everybody has to

  • have their safety glasses on.

  • Now the glasses I'm wearing are polycarbonate

  • lenses, which are shatter resistant, but when

  • I'm around energetic chemicals I always wear

  • the extra protection of goggles or side shades.

  • DEMO TIME!

  • I mean, to produce color you start

  • with a burning mixture, you need

  • an oxidizer and a fuel and then

  • you add the other ingredients,

  • the color producing ingredients to it.

  • This is a mixture of potassium perchlorate and red gum.

  • (INSTANT REPLAY )

  • (DRAMATIZATION)

  • Now instead of red,

  • now we want to produce green,

  • so we've added some barium carbonate.

  • Blue is the hardest color to produce pyrotechnically.

  • You need perfect chemistry.

  • This is copper oxide this is a red

  • flame composition, from strontium nitrate.

  • It's a very bright flame because it

  • has magnalium, a magnesium aluminum

  • alloy in the composition that

  • raises the flame temperature.

  • Now I’ve taken my base mixture and

  • added moderately coarse magnesium.

  • This should produce a nice white sparkle effect.

  • When I'm not sure exactly what's going

  • to happen when I test something,

  • I’ll use a little piece of fuse and

  • I light the fuse and it gives me the time

  • to step back just a short distance.

  • There goes the fuse.

  • AWESOME!

  • Fireworks make people happy.

  • There's something about watching that night sky

  • explode in color and sparks and noise that I think

  • really gets deep in the human soul and

  • seeing the night sky exploding in fire,

  • still brings chills to a lot of people.

THE CHEMISTRY

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B2 中高級

【歡慶2015】亮麗煙火背後的化學小知識 (The Chemistry of Fireworks - Reactions)

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    阿多賓 發佈於 2014 年 12 月 31 日
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