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Brain&Force
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Talent show - demos in 5 minutes or less?
At my school we're having a talent show. I wasn't planning to enter it, but they did like my idea of a chemistry demonstration, so I decided, "Why
not? Outreach is fun!"
So here's the thing. I have 5 minutes (likely more, but I just want to keep this short) to complete some interesting demos. As much as possible, I
want to have audience involvement. Here are some of my ideas. I don't have much access to chemicals in general, so assume I haven't done any of them
before. Some of these may be more physics than chemistry inclined. Please note I do not have access to a Bunsen burner.
Chemical chameleon (maybe with peroxide?)
Iodine clock reaction (possibly without starch for one run, just for variety)
Colored flames with copper, strontium, and potassium
Baking soda volcano with transition metal salts
Chemical garden with sodium silicate
Gallium/aluminum alloy and water (if I can find the gallium)
Amphoteric aluminum
Hydrogen peroxide decomposition/relighting of a glowing splint
Complexation cocktails with nickel, copper, cobalt, and possibly chromium
White-burning magnesium vs. green-burning ytterbium (maybe)
Permanganate and glycerin
Here are some more complex demos:
Curie temperature demo with terbium: a piece of terbium metal is shown to be only slightly paramagnetic, but cooling to dry ice temperatures changes
that property to significant ferromagnetism. I only have small pieces, though. If I can find gadolinium it'll work much better because I just need
regular ice.
Implosion demo: a sealable container is filled with extremely hot steam and then placed in freezing water, causing it to implode. I've seen this done
with an oil barrel once, but I don't know what scale I'd do this in.
Heat conduction demo: a block of aluminum and a block of plastic are touched by a volunteer. Because the aluminum conducts heat better, it feels
colder to the touch, but a piece of ice will melt faster when placed on it.
pH sensitive fluorescence: pyranine, the chemical that makes highlighter fluid fluoresce, appears to be sensitive to pH changes when it fluoresces
(the color becomes different). I have never seen this before, so I'll have to test it first.
These are possible, but I don't know if they can be approved.
Fake blood with iron/thiocyanate
Magnesium/silver nitrate flash powder
Lithium/sodium/potassium in water (I'd probably use this to make the alkali needed for the chemical chameleon. Or I could add indicator solution to
the water).
Any other ideas? I have an audition hopefully by Friday of next week (it may be earlier).
[Edited on 11.4.2014 by Brain&Force]
At the end of the day, simulating atoms doesn't beat working with the real things...
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DraconicAcid
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Sodium acetate supersaturation. Pour it and watch it solidify.
Mixing calcium acetate with ethanol/phenolphthalein- it turns pink and gels rapidly, then you can set the gel on fire.
If you're doing the fake blood, what you can also do is set up a series of beakers, each with a small amount of solution in the bottom. One contains
thiocyanate, one contains dilute salicylic acid, one contains tea, one contains sodium hydroxide, one contains iodide with some starch. Pour a
colourless, dilute solution of iron(III) chloride into each one....
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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Zephyr
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Draconic Acid, do you mean a reaction sort of like this?
https://www.youtube.com/watch?v=9NZvnVPuDKA
[Edited on 11-4-2014 by Pinkhippo11]
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Brain&Force
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What happens with the ferric chloride? I know about thiocyanate and hydroxide, and I probably don't have salicylic acid, but what about the tea and
the iodide? I know ferric iodide is unstable and converts to ferrous iodide and iodine. As for the tea, I have no idea what happens.
What is the calcium acetate used for in the gel demo? Can it be replaced with a different acetate for a different colored flame?
And I'd specifically like to ask if anybody's done anything with pyranine (highlighter fluid's fluorescent compound).
Also, please tell me which of my demos you don't think I should do. That'll help cut down on time.
[edit] Yay, I'm an national hazard!
[Edited on 11.4.2014 by Brain&Force]
At the end of the day, simulating atoms doesn't beat working with the real things...
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DraconicAcid
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Salicyclic acid can be made from aspirin easily enough- you don't need a lot. It turns purple (make it dilute, or it will look black). Tea turns
black.
With the calcium acetate, it's what makes the stuff gel when you add the alcohol. I don't know if other acetates would work very well.
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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gdflp
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Calcium acetate causes alcohols to thicken and gel. I don't think it can be replaced by another acetate. You could also try the methylene
blue/dextrose/sodium hydroxide reaction, though on second thought it might take too long.
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Zephyr
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The methylene blue reaction that gdflp mentioned can be easily adjusted to react in a certain amount of time using different ratios of dextrose to
sodium hydroxide.
Of the list you compiled my favorites would Chemical garden and the fake blood.
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Zyklon-A
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Lots of awesome and mostly safe reactions in this video.https://www.youtube.com/watch?v=ti_E2ZKZpC4#aid=P-tJI1xvIPk
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Chemosynthesis
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If not in a link, elephant's toothpaste and ghost crystals.
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bismuthate
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Reduction of dichromates or Vanadium (V) is amazing if you have the materials and would be allowed to do so.
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MrHomeScientist
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Gallium can of course be obtained from Gallium Source , and I got my gadolinium from United Nuclear.
The type of demos you do depends greatly on the age/background of the audience and how close they are to you. That tells you how advanced you can get
and how big the demo needs to be. One of my favorites is "penny alchemy" (my video) for close-up shows. This requires a heat source, though, which I also bought from United Nuclear (the butane micro
burner).
If you really aren't allowed to have open flames, I think the iodine clock is the most impressive. Modified slightly, it can be made even more
impressive as the iodine oscillator.
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Brain&Force
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So I've narrowed the demos down to a relatively small list of ones that will be in the program:
For starters, colored flames with methanol (I wanted to do the barking dog, but decided against it because I haven't been able to make it work).
Chemical chameleon
Fake blood with thiocyanate
Complexation/precipitation cocktails:
Nickel(II) with ammonia and chloride
Copper(II) with ammonia and chloride
Cobalt(II) with ammonia and chloride
Iron(III) with ammonia and thiocyanate
Iron(III) nitrate in water, then nitric acid
(Advise me on any complexes with ammonia, thiocyanate, or chloride that may be interesting)
Iodine clock (as a show-stopper). I'll just pretend the reaction failed or something. Anyone know the kinetics for this reaction?
I'll try to figure out if I can do sodium or potassium in water.
At the end of the day, simulating atoms doesn't beat working with the real things...
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Chemosynthesis
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Quote: Originally posted by Brain&Force  |
Iodine clock (as a show-stopper). I'll just pretend the reaction failed or something. Anyone know the kinetics for this reaction?
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Good choices. I'm glad you're doing outreach.
http://www.labandtheory.com/kinetics/kinetics-reaction-mecha...
That has your rate constants on the page if you scroll down.
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Brain&Force
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I'm setting it up differently:
Beaker A: Sulfuric acid, hydrogen peroxide
Beaker B: Thiosulfate, iodide, and starch
The kinetics you mentioned are different. But thanks anyway!
Now I have to gather the materials before Tuesday...
At the end of the day, simulating atoms doesn't beat working with the real things...
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Chemosynthesis
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| Quote: Originally posted by Brain&Force | I'm setting it up differently:
Beaker A: Sulfuric acid, hydrogen peroxide
Beaker B: Thiosulfate, iodide, and starch
The kinetics you mentioned are different. But thanks anyway!
Now I have to gather the materials before Tuesday... |
Oh, oops. This procedure?
http://papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_nos_ps_20.pdf
Do you want the rate law, or the actual constant?
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Oscilllator
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Elaphant toothpaste could be a good one, but make sure it works beforehand, since it can have a tendency to be rather anticlimactic.
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Artemus Gordon
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| Quote: Originally posted by Oscilllator | | Elaphant toothpaste could be a good one, but make sure it works beforehand, since it can have a tendency to be rather anticlimactic.
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Really? I can see how old H2O2 could cause problems. What else could?
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Oscilllator
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Low concentrations of potassium iodide, a wide-necked flask (use a volumetric one if possible) and possibly low temperature of initial reactants. You
might want to try MnO2 as a catalyst instead, see how that goes.
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MrHomeScientist
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I do the elephant toothpaste demo all the time as part of my outreach. In my method, I have ~125mL 35% H2O2 in a large plastic
graduated cylinder (I think 1 liter? It's about 2 inches in diameter). Solution 2 is 14g KI in 10mL water, in a small beaker. When ready, quickly dump
all of the beaker into the cylinder and step back! I have my cylinder sitting inside a shallow plastic tub, which usually catches most of the foam.
My toothpaste wasn't working as well not too long ago, so I experimented a bit to fix it. Increasing the concentration of the KI solution to what I
wrote above seems to have done the trick (used to use 12g). Not sure why it started failing in the first place, though, since my peroxide and iodide
both tested to still be perfectly good.
Volumetric flask is a great idea - I bet that would look a lot like silly string!
Brain&Force: What problems are you having with the barking dog? That's another one I do regularly for the show. Definitely my
favorite demo.
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Brain&Force
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I'm not doing elephant toothpaste - too messy.
The problem I have with the barking dog is that I can't get the alcohol (methanol) to ignite. How do you set yours up? I'll also try copper chloride
for color. Or is boric acid better?
I'm also going to attempt to acquire sodium or potassium, if possible.
I also wanted to do the ignition of glycerin with permanganate, but one of my teachers said he doesn't want to have me mess with oxidizers. 
Also, does 3% peroxide work with the iodine clock?
[Edited on 14.4.2014 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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"Doesn't want to mess with oxidizers"? Ah, that's too bad. He's just effectively ruled out ~80% of the best reactions. Can you concentrate you
peroxide?
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MrHomeScientist
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The way I do the barking dog isn't about accurate measurment, but it works quite nicely for my purposes. I have a long glass tube (~4 ft long x 1.5 in
wide) that I lay on a tabletop. One rubber stopper is very loosely fit into the far end of the tube. I take a balloon and fill it with nitrous oxide
gas (from a lecture bottle tank) to a certain size, then weigh it to make sure it's somewhere in the neighborhood of 0.5 - 1.0 g. My lab scale is
actually too sensitive to get a good reading this way, so I just ballpark it. I then take the balloon, attach a short length of PVC tubing to the end,
insert the tubing into the glass tube, and slowly let the nitrous out of the balloon. This, plus the loose stopper at the other end, helps to mix the
gas with air inside the tube instead of just blowing it all out the other end. I'm certainly losing some nitrous this way, but it still works. (It's
the same density as air so there's really no good way to do this, except water displacement.) After filling, I quickly firmly stopper both ends and
secure with electrical tape for transport.
Next, I take two small spatula-fulls of boric acid (probably something like 0.25 g) and place this in a tiny vial. I then add 1 mL of methanol, and
shake until dissolved.
On demo day, I pour this vial into the big tube, replace the stoppers, and swirl around to vaporize the alcohol. You need to vent a few times to
relieve excess pressure. I usually do this about 30 minutes before the demo, to evaporate as much as possible. I then stand it upright in a tube stand
I made, uncork the top and ignite with a long BBQ grill lighter. Works every time!
Boric acid is ideal here because it not only dissolves in methanol, but also reacts to form trimethylborate, which is very volatile and imparts a
strong and uniform green color. I haven't tried other coloring agents.
For Na and K metals, try galliumsource. I haven't used them myself but I hear lots of good things around here.
The iodine oscillator I perform uses 4.0M hydrogen peroxide, which I make by diluting some 35% peroxide I have. I think this equates to about 15%
concentration. I have a feeling it won't work very well with just 3%. Worth a try if that's all you have. Try pool supply stores for higher
concentration - I found 27% as a chlorine-free oxidizer called Baquashock.
No oxidizers? Don't tell him about the nitrous oxide, hydrogen peroxide, or nitric acid he's apparently ok with!
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Brain&Force
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Never mind, I got the barking dog to work! I didn't add any coloring agents though...I'll try strontium/lithium, potassium and copper. I have boric
acid somewhere.
The "barking dog" refers to burning methanol in a volumetric flask, not the nitrous oxide/carbon disulfide reaction.
I lit it in front of a room full of people and they all suddenly turned and looked at me. It really does grab audience attention!
This is only one of my teachers, Zyklonb; I think the other one trusts me more.
[Edited on 14.4.2014 by Brain&Force]
At the end of the day, simulating atoms doesn't beat working with the real things...
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MrHomeScientist
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Nice! I actually use a different version of the barking dog than the standard one with CS2 (as described above), but it behaves in much the
same way. Just green instead of blue, and it produces no irritating fumes (SO2 in the blue version). Your demo would technically be termed
more of a "whoosh bottle" I think  I have doubts about coloring agents in that
case, though. The green one works so well because it makes a volatile compound. Dissolved salts would simply crystallize out on the walls of your
container, rather than contributing to flame color. I could certainly be wrong though! Let us know how it goes.
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bismuthate
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Tonight I had a science fair and I brought in a small version of the Briggs-Rauscher reaction in as a demo and the people were amazed.
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