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Surprising Science Demonstrations?
An anonymous reader writes: "I have been called upon to conduct some science workshops for children of various ages, and I'm looking for some good demos. In particular, I've found that demos are most effective at getting students to think when they give a surprising or unexpected result, such as the classic two-slit experiment (or, for the extreme crowd, demonstrating the Leidenfrost effect by sticking one's hand into a vat of molten lead [PDF]). I'd like the Slashdot crowd's suggestions." Please don't do the lead one.
this worked before in a chemistry demo i gave in high school. It gives an unexpected result and it is colorful to boot :-) http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA2/MAIN /AMFOUNT1/CD2R1.HTM for more details
put a little wax in a foil dish, heat it over an Bunsen burner, then squirt water at it... HUGE fireball... People don't think it will happen, but it does, it also seems to be safer than oil
Another one my chem teacher did was taking water and separating it into oxygen and hydrogen by using a battery and matching the terminals, then letting the hydrogen into a test tube and light it to make a loud "pop!"
Also, anything that disolves metal with a liquid is good, like magnesium and acid or such.
1: Using compressed air to shoot a pencil through a peice off 1/2 inch thick plywood
2: Using a large solenoid to magnetically rip apart an aluminum can (can is placed in the center of the circle of wires and large AC is momentarily applied)
3: Pouring liquid nitrogen on your hand (the back, not your cupped hand)
4: Making liquid nitrogen ice cream (pour some LN2 into a cup of milk, stir rapidly)
5 Superconducting magnetic levitation (small permanent magnet over a critically cooled superconductor)
6:The ever classic fire extinguisher used to propel a person across a room in a rolling chair
7: compairing the explosions made by a baloon filled with air and h2, h2, and one with both H2 and O2 in proper amounts
The University of Wisconsin has a site at http://genchem.chem.wisc.edu/demonstrations/ that contains links to dozens of demos (with raitings) for various categories. I'm sure there is something for each age/interest level there
I would suggest the use of a microwave oven and a variety of things, my favorites are:
1: Lightbulb, metal in milk to insulate, don't use anything with mercury in it.
2: CD-Rom (all kinds work, try different ones)
3: place a toothpick in a peice of cork, place in center of microwave, place 3 peices of cork around center cork and support fishbowl(any peice of glass that is globe like will work, the more like a globe the better) light the toothpick, place glass on top of corks around edge(for ventilation) and start microwave
4. grape, cut the grape in half, then carefully slice the grape again in half, but leave small peice of skin connecting quarters. Fold together to make a flat side and place on microwave floor.
Hints: use old microwave, preferably with clear front faraday cage setup, in addition to this also place a glass of water in the back of the microwave to avoid destroying the magnetio. Tinfoil and other items are fun too, play around and have fun. Ohhh yea, no gerbils etc. Have fun.
Theodore Gray, of Mathematica fame, and recent winner of an IgNobel prize for his wooden periodic table table has a page nicely documenting what happens when you drop sodium into water, which includes a nice quicktime video of a drop of sodium into a lake.
It's psychosomatic. You need a lobotomy. I'll get a saw.
But better than a demonstration is anything hands-on, especially with young kids. You can do some cool stuff with the new neodymium magnets. You can hook up an oscilloscope to a microphone and let them look at their voices. (Or use computer oscilloscope software.)
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(or, for the extreme crowd, demonstrating the Leidenfrost effect by sticking one's hand into a vat of molten lead [PDF]).
Ah yes, this would be the one where the paper says, "Never, ever do this.". [If you use too much water, you get a steam explosion that sends molten lead everywhere.]
You might be able to do a safer variant by dipping apples or bananas or what-have-you, though, with a blast shield between the crucible and the audience, though (and a leather apron and gauntlets and visor, unless you *like* liquid metal scars).
Suspend a cinder brick (or other heavy object) from the ceiling with a rope. Pull it back until it just touches your forehead and let go so it swings like a pendulum. It you don't move, it will just touch your forehead on the return swing (or a little short of it). Listen to the gasps of horror from those in your audience who think your head is about to be smashed.
Yet Another Web Site
The Physics department head at the college I attended was constantly doing High school demos.
One I found interesting involved a long aluminum pipe a steel cylinder just small enough to fit in the pipe and a cylindrical magnet (or cylider containing a magnet) of the same size.
First demonstate that the magnet is not attracted to the aluminum by pressing against the pipe.
Then drop the steel slug through the pipe. It should slide through unhindered and quickly fall out the other side.
Now drop the magnet through the pipe. The moving magnet will induce an electric field in the pipe which in turn induces a magnetic field and slows the magnet. And hence it falls very slowly.
Then of course there are the two syringes of different diameter coupled by a plastic tube to illustrate hydraulics.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
If you were to release the cinder block with the flat side facing you and the rope attached in the middle, were it to turn in mid-swing and come back with at a 45 degree angle to the release position it would most surely split the skin from hairline to eyebrow.
- Get a lightweight, 2-prong extension cord.
- Do not plug it in yet.
- Bare the ends, and wrap them around two medium-large nails.
- Insert the nails into the pickle.
- With all hands off the pickle and the bare metal, plug in the cord.
- Observe that the pickle glows around the contact points with the nails.
Caution:- Never tough the pickle or the bare metal while the cord is plugged in: shock hazard (duh
:-)
- Put the pickle on a non-conductive surface, e.g. sheet of wood.
- Consider doing it out doors, as it smokes and is smelly.
- Adult supervision required. You assume all risk.
Crispin----
Crispin Cowan, Ph.D.
Chief Scientist, WireX Communications, Inc.
Immunix: Security Hardened Linux Distribution
Available for purchase
A stream of water is split in two using a tubing "tee". Each stream then is allowed to drop through a bottomless can and into a catching can. The pairs of cans are crosswired and well-insulated. With the water streams breaking up into droplets as they pass through the bottomless cans, an initially slight imbalance of charge is amplified until a spark jumps between them. Typically a 1" spark can be attained after flow of 30 seconds or so. As the charge grows, the water dropplets of each stream repel each other providing an indication of the voltage buildup. If the weather is humid or the insulation of the cans inadequate, the charge leaks away without jumping the gap.
A google search on "Kelvin Water Drop Experiment" gives lots of additional info.
Potassium Permanganate?
It's dark purple, and is rather impressive when mixed with glycerin...
This is a thoroughly spectacular demonstration of many physical and chemical properties and concepts.
Make a dry mix of pulverised Aluminium and Iodine.
Then pour a small cone of the mix onto a fireproof base (my chem teacher used an asbestos sheet, but I'm not sure if asbestos is used in schools any longer). Make a small well in the top of the cone. The mixture is stable, right?
Well, watch what happens to the mixture when you put a single drop of water in the well. You get a plume of purple smoke and a handful of sparks.
The real question to ask the kids is "Why didn't the reaction begin until the water was added?".
IIRC, it goes something like this:
When Iodine dissolves in water, some of it hydrolyses into an acid (hydroiodic?) which reduces the oxide film on some the aluminium, leaving bare elemental Aluminium in contact with water, oxidising it. The heat from the water oxidising the Aluminium sublimes the Iodine, creating the purple plumes and melts more Aluminium leaving bare Aluminium in contact with oxygen in the air, starting the main reaction.
You might want to use a fume hood, though, gaseous Iodine is a little unpleasant.
Ahh - My eye!
The doctor said I'm not supposed to get Slashdot in it!
I do believe you're remembering this incorrectly. Yes, H20 will be the result of burning H2 and O2, but it'll be in the form of water vapor, not a liquid.
Also, remember that H2O expands something like 500+ times in volume when turning into a gas. That would have had to be one helluva balloon to make a "crapload" of water.
http://kered.org
I much rather like demonstrations that are counter-intuitive. Especially things that seem "supernatural" to do, yet are very natural indeed. I'd like to point out the work of David Willey, whom I've worked with. He organized a world-record firewalk, and I attended (yeah, I've got a world record in firewalking... :-) ).
Check out his article in Skeptical Inquirer: The Physics Behind Four Amazing Demonstrations.
David has done quite a lot of explosions and rocketry too, he knows all about that too, but his best demos is really those that seem risky, but are not. The liquid lead is among them.
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actually any more, they have a harmless chemical that is a VERY good stabilizer (*sigh, been what, 4 years since college chem? You'd think I'd remember this much), which slows down the breakdown process (since H2O is the stable atom, H2O2 is very unstable, thus why it breaks down to H2O and O [the single O being the actual oxidizer] or 2H2O2 => 2H20 + O2 given the lack of a catalist). But the long and short is that you can now keep home or laboratory grade hydrogen peroxide on the shelf for a long time.
I remember in chem class chunking the crust off the H2O2 bottle, and turning my finger tips white just from that (with out getting any moisture on my hands), because the stabilizing agent was so good that even dried there was still plenty of H2O2.
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