15.2 What are good outdoor/indoor chemistry demonstrations? p6
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This article is from the Chemistry FAQ, by Bruce Hamilton B.Hamilton@irl.cri.nz with numerous contributions by others.
15.2 What are good outdoor/indoor chemistry demonstrations? p6
From:webbb@mbf.UUCP ( Bryan Webb )
I didn't see the originating message of this thread, but from the
responses that have made it here, I think this is the kind of stuff
you might be looking for. In earlier times, I've done these:
1) Place a small pile (several grams) of powdered magnesium on a surface
you don't care about in an environment provided with plenty of
ventilation. On top of this, place a couple of grams of powdered
iodine (well, as close as you can get to it, though that might not
be crucial). Now, put a couple drops of water on the iodine ...
enough to also contact the magnesium ... and stand back. The heat
of the reaction vaporizes some of the remaining iodine into a purple
vapor.
2) This is pretty dangerous, so be very careful. Take a couple of grams
of red phosphorous and place on top of a couple of grams of potassium
iodate. Rapidly stand back... spontaneous combustion. My experience
was a time delay of a couple of seconds, but I wouldn't want to count
on it... I discovered this accidentally... boy was I surprised. The
speed of the reaction may be related to the humidity.
3) Potassium dichromate is normally bright orange at room temperatures. If
it is cooled to liquid nitrogen temperatures, it becomes yellow. If
heated, it becomes a deeper red color. I'm not aware of any other
inorganics that have this range of color change when the temperature
is varied.
4) Ahhh, my favorite... When I was in high school, I took the 2nd year
chemistry class that was offered. We had the resources of the
school at our disposal, so long as the experiment we wanted to do
was "in a book". The book I had was "Chemistry Magic", and described
an "experiment" where some cotton balls were placed on a fireproof
surface, a few grams of Sodium Peroxide was placed on top, and then
you put a drop or two of water that will wet at least a little bit
of both the peroxide and the cotton.
It's a long story, but I this experiment worked, at least on other
cellulose objects like paper towels. In fact, the fire in the
metal trash basket was hot enough to melt/burn away the bottom,
the linoleum underneath, and some of the concrete in the floor.
The flames formed a "solid" yellow flame and lots of thick white
smoke (containing NaOH dust). You really don't want to breathe
this stuff. We didn't, anyway :-)
5) Oh, another thing we did in that class was take the gas outlet used
for the bunsen burners and direct it into a test tube that was
partially submerged in liquid nitrogen. (The whole system was
sealed.) The gas condenses into a liquid... the only problem
was safe disposal. It helps to plan ahead! :-)
[ Note that nuke@reed.edu subsequently supplied the following warning ]
" If you decide to try this be aware that liquid nitrogen will condense
liquid oxygen in a vessel open to the air immersed in it. Liquid O2
forms explosive mixtures with many organics. IF you still want to try
it, immerse the tube in the nitrogen and then immediately run the gas
in. only do a little bit. How much you get depends on what proportion
of weights of low hydrocarbons the gas contains ( I think methane
condenses at this temp, but not quantitatively like some stuff, unless
there is a large surface area)."
6) One of my classmates made luciferin [sic]. It's a liquid that
glows in the dark for about 12 hours. That was fun too!
Happy researching!
Standard disclaimers apply; I'm not sure my company would have hired
me if they had the foregoing admissions before them.
Non-standard disclaimers too: I don't recommend you do any of these things
either.
From: fred@theory.chem.pitt.edu < fred >
If you would like to condense out methane gas in a relatively safe way,
fill a balloon with the gas and THEN condense the gas with liquid N2.
You can use scissors to cut the balloon, and pour the liquid CH4 into
a beaker with water in it (notice that it floats, forms ice, etc.) and
light it. Only the fumes burn as they mix with atmospheric oxygen.
This makes a fair "olympic torch." Wear goggles etc.
From: Larry (Call me "Lefty") C
One that can be safely performed with a long enough spatula.
Mix Calcium Carbide with any strong oxidizer (KMnO4, NaNO3, even MnO2
works). Proportions aren't real important here.
Using face shield, gloves, lab coat and long spatula, drop a SMALL
amount (say, 1 gram or so) of this into common household bleach.
Acetylene and chlorine are evolved, which immediately, uh... exploded
Delightful chlorinated hydrocarbons result, unfortunately :(
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