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Author: Subject: I want to hear your favorite chemistry demonstrations
SAACS
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thumbup.gif posted on 6-2-2014 at 08:42
I want to hear your favorite chemistry demonstrations


Every year our university chem club goes to a children's museum and conducts some interesting demonstrations for the age range of roughly K-5. Some examples are: gummy bear + KClO3, elephant toothpaste, and a ball pit explosion using a bottle filled with LN2 in a trash can. We bring plenty of LN2 and have access to a lab and other ways of getting any necessary materials. The only caveat is that while we can work inside or outside, we have no fume hoods at the children's museum.

What demonstrations do you like the most?
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Pyro
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[*] posted on 6-2-2014 at 08:44


chemical chameleon is nice



all above information is intellectual property of Pyro. :D
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Zyklon-A
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[*] posted on 6-2-2014 at 08:55


Water-initiated flash powder.
Chloric acid (from KClO3+H2SO4) and sugar.
Aluminium and iodine plus a few drops of water.
About .5 gram NH3, nice iodine vapor, initiated with feather.
Sodium peroxide + sugar and add drop of water to get going.


[Edited on 6-2-2014 by Zyklonb]




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Mailinmypocket
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[*] posted on 6-2-2014 at 08:56


Tossing a small scooop of KMnO4 into a tall beaker with a small layer of 35% H2O2 in the bottom makes an impressive little mushroom cloud poof out. Be careful though, it is like elephants toothpaste but can spit a little if you use too much peroxide or the container is too small. You can also submerge a glowing splint into the beaker to demonstrate O2.

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Brain&Force
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[*] posted on 6-2-2014 at 09:30


Fluorescence of pyranine (found in highlighters)
Tollen's reagent
Bismuth diamagnetism
Coordination chemistry of Ni2+ and Cu2+ with ethylenediamine, ammonia and chloride
Burning magnesium and spraying water on it
Gummy bear in chlorate
Flame tests in methanol/ethanol
Fake blood (iron thiocyanate)
Heating iodine
Reaction of aluminum with iodine
Ammonium chloride smoke
Aluminum with copper chloride/HCl
Alkali metals in water
Precipitation of unusually colored precipitates (cobalt hydroxide, lead iodide)
Dichromate redox
Iodine clock
I could go on forever...

[Edited on 6-2-2014 by Brain&Force]




At the end of the day, simulating atoms doesn't beat working with the real things...
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Zyklon-A
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[*] posted on 6-2-2014 at 09:35


What do you mean ''Burning magnesium in water''? Do you mean spray water on a burning Mg ribbon, or what?




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Mailinmypocket
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[*] posted on 6-2-2014 at 09:44


Burning Magnesium in Water
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MrHomeScientist
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[*] posted on 7-2-2014 at 07:28


I actually do a science stage show for the same target audience. We go to local elementary schools and do a 45 minute show to get the kids interested in STEM (Science, Technology, Engineering, and Math) career fields. We have videos and a couple experiment descriptions on our website, www.sciencebrothers.org .

My favorite demonstration of our show is the Barking Dog. Thanks to woelen here on this site, I use a much safer version that produces a green flame instead of the usual blue*. Elephant Toothpaste is probably the most popular with the kids. The chemical traffic light is also pretty good and simple, and by using the same chemicals with a different dye you can change it up and perform the Blue Bottle demo.

I really enjoy doing the show. It's a great feeling to see kids get so excited about science. Good luck with yours!


*Edit: To clarify: it's safer because it replaces carbon disulfide with methanol with a little boric acid dissolved in it. The standard barking dog produces sulfur and sulfur dioxide as products, which make cleaning the tube annoying and produces sore throats, respectively. Using methanol/boric acid instead results in harmless byproducts (boron trioxide, most likely) and the tube cleans out easily with a water rinse.

[Edited on 2-7-2014 by MrHomeScientist]
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confused
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[*] posted on 7-2-2014 at 07:52


i like the iodine clock reaction, never fails to amaze people
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[*] posted on 7-2-2014 at 10:00


By far my favorite demos are:
1) Hydrogen Balloons
2) Metal salts in a flame
3) Whoosh Jug (Ethanol in a large office water jug, vaporized, and ignited)

-Sarge




The Home Chemist Book web page and PDF. Help if you want to make Home Chemist history! http://www.bromicacid.com/bookprogress.htm
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[*] posted on 7-2-2014 at 14:15


1) Oxidation states of Vanadium using amalgamated zinc and Cerium (IV) to re-oxidize it back to its so so yellow: Kinda advanced but shows some nice analytical technique with beautiful color changes especially the 3+ blue… mmmm….ok maybe not for K-5 but hey it hooked me on chemistry….

2) Liquid oxygens paramagnetism and blue color: Nice way to talk about spin and free electrons and the color blue… also good for showing big flames at the end.

3) Thermal decomposition of Iron oxalate to pyrophoric Iron: Fire is always nice, fire is even more fun when all you need is air…. nice way to show how a nail can catch fire if you can smash it up enough. Oh and you can even drop the pyrophoric iron into the liquid oxygen for a big kicks!




Ascaridole, the masked bandit of chemistry!
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Zyklon-A
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[*] posted on 7-2-2014 at 19:45


On a related note to 'Burning Magnesium in Water', Al can also react with water in an even more spectacular way than the Mg in the video. Make an un-stoichiometric 'flash powder', by mixing about 1 gram of KClO3 for every 4.5-6 grams of Al.*
Light it with a fuse and then wait for it to stop burning, then most of the Al will not have burned, but it will still be glowing red hot. Take a syringe (or pipette) full of water and spray a lot of water on the pile of glowing Al. It will instantly burst into a bright white flames as the Al reduces the water to H2 , and on top of the pile the H2 will react with more oxygen in the air and give off a nice blue flame, very pretty.

*The reaction looks much better in larger quantities than 1g KClO3 and ~5g Al. For best results try 3g KClO3 with ~15g Al. If a lot of water is sprayed on that, it will likely Fizz for a couple seconds then erupt into bright white flames, shooting burning Al in all directions! (looks a lot like fireworks).;)
Be very carful with this and if you show the reaction to kids, absolutely do not do it inside! Also try it a few times yourself before showing to anyone, just to get the hang of it. And wear all necessary protective clothing, if the reaction goes well, it is worth the effort.



[Edited on 8-2-2014 by Zyklonb]




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[*] posted on 7-2-2014 at 20:08


I'll answer
this : http://www.youtube.com/watch?v=2udiRj6vYag

and this : http://www.youtube.com/watch?v=h4pNXAtPJp8

The first one is way too toxic to be performed without fume hood with kids, but it is so great :D The seconth one might be doable outside.

Also, simply "dissolving" styrofoam into acetone can be rather impressive and this one is totally safe! http://youtu.be/6S4zfMdjQxY?t=1m11s

[Edited on 8-2-2014 by alexleyenda]
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Zyklon-A
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[*] posted on 7-2-2014 at 20:19


Wow! That first video was badass, I've seen both of those reactions, but not at the same time.



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[*] posted on 8-2-2014 at 09:36


Yup both at the same time is really awesome, it looks like the doors of hell opening :p
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[*] posted on 14-2-2014 at 19:22


I'm really glad to hear people are still involved in their communities with science outreach. I always liked iodine clock and oscillatory reactions since they really made me see equilibrium in a different manner than prior.
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[*] posted on 22-2-2014 at 22:49


Try a drop of CS2 and let it avaporate in a measuring cylender and ingest N2O with a syrenge into the cylender.there will be very bright blue light and a strange sound,barking dog!!!!
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Mailinmypocket
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[*] posted on 2-4-2014 at 04:51


This isn't the coolest or my favorite but I did find it original, that's for sure. Blue bottle demo, edible style.

http://www.stevespanglerscience.com/color-changing-powerade
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[*] posted on 2-4-2014 at 06:15


That's astonishing. Great find!

The standard blue bottle requires dextrose, sodium hydroxide, and methylene blue. In his version, the dextrose would be from the Sweet N Low and I imagine the dye is in the Powerade. But tonic water is acidic, so there must be something in the cinnamon Altoid, and only the cinnamon variety, that basifies the solution. Very very interesting. I wonder how he discovered something like that; seems like a pretty random combination.
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[*] posted on 2-4-2014 at 07:28


Quote: Originally posted by sasan  
Try a drop of CS2 and let it avaporate in a measuring cylender and ingest N2O with a syrenge into the cylender.there will be very bright blue light and a strange sound,barking dog!!!!


Please note- the word you want is "inject". To ingest something means to eat or drink it. (And I think the barking dog uses NO, not N2O.)




Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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MrHomeScientist
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[*] posted on 2-4-2014 at 08:13


I routinely perform the barking dog with nitrous oxide, N2O, and it works great. And you need a source of ignition to get the reaction to start - just mixing CS2 and N2O in a flask doesn't do anything.
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[*] posted on 2-4-2014 at 08:24


Would helium affect the pitch of the bark?
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[*] posted on 2-4-2014 at 09:10


Quote: Originally posted by MrHomeScientist  
I routinely perform the barking dog with nitrous oxide, N2O, and it works great. And you need a source of ignition to get the reaction to start - just mixing CS2 and N2O in a flask doesn't do anything.


Okay. I do know that it *does* work with NO- I was shown how to do it, generating NO from copper/nitric acid (and scrubbing the gas well with water to remove NO2, which would have detonated).




Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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[*] posted on 24-3-2016 at 04:20


I tried to perform the elephant toothpaste reaction many times today without very impressive results,

I first tried 50ml of 50% H2O2, 5g potassium iodide solution, 25ml kitchen detergent (poor result) followed by the same amounts but replacing the kitchen detergent with sugar soap ( a little better this time)

Then I tried the same amounts of H2O2 and potassium iodide with a much smaller, unmeasured amount of sugar soap but still didn't achieve the impressive expansion of foam expected with this novelty reaction.

I thought it could be an issue with the 2 different bottles of H2O2 I tried and have had in storage for a long time so I bought a fresh bottle at the local hydroponic store but still had the same results.

Any ideas what might be going wrong?

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MrHomeScientist
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[*] posted on 24-3-2016 at 09:22


Three things:
- How concentrated is your "potassium iodide solution"?
- You're using a ton of soap, which I'm sure is diluting and slowing the reaction.
- You can easily check the concentration of your peroxide to make sure it hasn't degraded by measuring the density, and using this calculator.

Our version of elephant toothpaste uses 125mL of 35% H<sub>2</sub>O<sub>2</sub> with maybe < 10mL liquid dish soap, just enough to lightly color the solution and produce bubbles. To this we quickly add a solution of 12g KI in 10mL water (so, a saturated KI solution). This is done in a 1000mL plastic graduated cylinder, and shoots a column of foam out the top several feet in the air.

One time the manufacturer accidentally filled one of our 35% bottles with 50% peroxide, and using the same conditions as above blasted the foam out instantaneously, spraying hot foam onto the presenters. Scary situation. Now we test each new bottle of peroxide before use. Be careful with that strength of peroxide.
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