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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.
There's always a chunk of sodium and a beaker full of water.
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The inanimate carbon rod?
"In rod we trust"
I always had fun loading hydrocloric acid into a supersoaker-100 when I was a kid. You can buy it at any pool store. I could make nice messages in people's lawns with it.
Boy did I confuse the hell out of me ex-girlfriend when I wrote "I'm a dyke" in 15 foot letters into her lawn. She wondered how I did it since it was written in such nice cursive. I denied everything of course since her dad would beat the sh*t out of me. Its also fun to shoot at metal objects with it. I rusted a stop sign and broke off the pole in just 3 minutes. I had my supersoaker pumped high and I shot it with alot of pressure. The poisionous gas clouds that mist outward from the gun kind of suck though. Yes it can sting and burn your lungs.
I am glad I matured beyond this. However if I lived in Redmond Washington, I would probably still have alot of fun doing this.
http://saveie6.com/
Any experiment requiring a blast shield get's my vote. "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)."
>>>Yes it can sting and burn your lungs.
Hey, guess what, the stinging and burning was just a symptom of the problem. The problem was that you damaged part of your lungs while inhailing those fumes at close range.
Although you don't quite qualify for the darwin awards...
~A'Ëq'i4d)^'$ÊSÈòB
Although you don't quite qualify for the darwin awards...
Oh, come on, isn't there some kind of Darwin Honorable Mention that we can give him? Lord knows he deserves it....
I write in my journal
>>3: Pouring liquid nitrogen on your hand (the back, not your cupped hand)
This would dovetail nicely with the molten lead demonstration.
And, in all likelihood, you could wrap up the session with the ever-popular "trip to the emergency room" demonstration.
I write in my journal
This demo (which works very well) shows conservation of momentum. The tennis ball or basketball bounced alone will hit the floor with velocity V relative to the floor and rebound with velocity -V relative to the floor. When you drop the tennisball/basketball combo, the basketball hits the floor first, rebounding with velocity -V as before. The tennis ball, which is still moving downwards, then immediately collides with it at a relative velocity of 2V. The tennis ball rebounds with velocity -2V relative to the basketball, which is itself moving upwards at velocity -V, so the tennis ball moves upwards at -3V relative to the ground. Since the height attained goes as the square of the velocity (kinetic energy going like velocity squared and potential energy change due to gravity being linear in the distance ascended) the tennis ball travels nine times higher.
:-).
I've also done this demo with three balls stacked on each other. It's much harder to get them all aligned, but when it works, the topmost ball goes (optimally) forty nine times higher than when bounced alone.
Note that the momentum conservation equations that give the perfect reversal of relative velocity assume that one object in the collision is much more massive than the other (i.e. basketball versus earth and tennis ball versus basketball). In this limit, the velocity of the more massive object is essentially unchanged by the collision.
Once, for fun, I calculated that if you extended the stack of balls to something like 20 that the topmost ball would attain orbital velocity
Curtains for windows?
At http://www.wiley.com/legacy/college/phy/halliday32 0005/pdf/leidenfrost_essay.pdf at the end.
"I have long argued that degree-granting programs should employ ''fire-walking'' as a last exam. The chairperson of the program should wait on the far side of a bed of red-hot coals while a degree candidate is forced to walk over the coals. If the candidate's belief in physics is strong
enough that the feet are left undamaged, the chairperson hands the candidate a graduation certificate. The test would be more revealing than traditional final exams."
I'm all for it! This will show whether they really believe in the scientific method in their guts.
(Fortunately I completed my undergrad in May)
The only reason all cover-ups appear to fail is that you never hear about the ones that succeed.
My favourite experiment was when my chemistry teacher was introducing us to liquid nitrogen. As he was talking he had a large thermos of the stuff sitting on the table. He put on his lab gloves as he was talking, and then put his had into the thermos with his first finger dipped into the nitrogen. When he got the part where he was explaining how objects soaked in nitrogen turn brittle, he pulled his hand out of the thermos, and smacked his first finger against the edge of the counter. The collective gasp from the students when his finger shattered was followed by total silence (or was there some screaming too?). What he has done is "loaded" the glove with a piece of sausage in the finger of the glove - when he had his hand in the nitrogen, it was safely curled up in a fist! Needless to say, the demonstration was effective, and we were all very carefull when handling liquid nitrogen.
My hs physics teacher was fond of his suspended bowling ball and used it in numerous demonstrations--all very well and good until the support breaks and the ball flies into an unsuspecting student.
Moral of the story--Flying bowling balls have a considerable amount of momentum, and they hurt.
Hey, he may not get the Nobel, but for sure he can acheive the Darwin.
NOTE: I've seen a professor sucessfully fail at this experiment, with a little impact crater on his face.
Easy way out. Just say,
"I made a crater on my face on purpose because today is Astronomy Day, kids!"
Table-ized A.I.
Pickles flouresce (glow) when subjected to 120VAC
Extra credit for anybody who eats it when done.
Table-ized A.I.
This is one of my alltime favorites. I've been thinking about getting a vacuum pump so that I can do it in the comfort of my own home.
One cup of water in a vacuum chanber. Pump out the atmosphere. Water boils until only the low energy water is left, which then freezes.
Gee, you really went in a different direction in the second paragraph from where I thought you were going in the first.
I did this in my apartment at college during a New Year's Eve party. The thing nobody ever mentioned before that is it really, REALLY STINKS!
Do this outside or in a well-ventilated area. Do not chase your guests out into the cold dark night. Well, it was Pasadena, CA, so it wasn't that cold, but still -- beware the stinky pickle.
Also beware the stinky, half cooked pickle after it's sat out on the deck for the next month.
"Genius may have its limitations, but stupidity is not thus handicapped." --Elbert Hubbard (1856-1915)
In high school we had lots of explosions in physics class. Only one was unintentional. The teacher was demonstrating Ohm's law hooked a tungsten wire to a car battery. It glowed red hot. He then added two more wires (nine times the power) in parallel and the wires glowed white hot and then turned to liquid and dropped onto the battery. Seeing the fire, one of the kids yelled, "She's gonna blow" as a joke, but it seemed likely so many of us covered our faces. The battery exploded at that moment. I was on the front row and didn't notice any ill effects. The next day my pants came out of the washer missing the entire front of them. My shirt was in a similar condition. The chalkboard in the classroom was white except for the outline of the teacher's profile. You could see that he held his arms up to cover his face.
Lasers Controlled Games!
The chalkboard in the classroom was white except for the outline of the teacher's profile. You could see that he held his arms up to cover his face.
Wow. Just like what happens to the coyote in "Road Runner".
"Backups are for wimps. Real men upload their data to an FTP site and have everyone else mirror it." -- Linus Torvalds
I had a chem lecturer who did just this very demonstration as a fun way of introducing emission spectra (pickles contain high quantities of sodium, making the pickle act like a sodium lamp). As the demo wore one the glow from the pickle decreased, presumably because some chemical change in the pickle wrought by having large quantites of current pumped through it tied up the sodium. To compensate, the lecturer cranked up the voltage on the power supply he was using, which worked fine until his hand slipped and he accidentally ramped the voltage all the way up to the supply's highest setting (240V IIRC).
Needless to say, this was well in excess of the pickle's tolerances, and it exploded, showering fat orange sparks everywhere (nearly catching an unlucky student volunteer involved in the demo) and sending an almighty stink throughout the lecture theatre. So bear in mind that a pickle has exactly the same limitations as any other electrical component when doing this experiment.
Ah, first-year chem, those were the days. Exploding pickles, naked guys wandering into lectures...ahem, exucse me, I digress...
You haven't lived till you created plasma balls by shorting an AT power supply that was between your legs at the time. (this wasn't the intended goal)
Or, more likely... "I bade a crader on by pace begause doday is Astrodoby Day, gids!"
"The best argument against democracy is a five minute chat with the average voter."
--Winston Churchill
> 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.
Yeah, but the whole point was to educate the children by entertaining them!
Sheesh, evil *and* a jerk. -- Jade
that same teacher showed us a kinda cool experiment herself. drain about 1/4 of the coke out of a 2-liter coke bottle, and drill a very small hole in its cap (the smaller, the better). next, take about a roll of mentos (the original kind, i think, test it out yourself), and place small holes through the center of each. now take some fishing wire and thread them through all the mentos in a line, and tie the ends with something heavy like steel nuts. make sure the mentos are tied together tight, and give a little extra fishing wire on one side. thread this extra fishing wire into the bottom of that coke cap with the hole in it, and screw the cap on the coke bottle, holding the fishing wire to make sure the mentos do not touch the coke inside. drop the wire to let the mentos drop into the coke, and move out of the way. some odd reaction takes place that causes the cap to shoot off and hit the ceiling, and pop spews close to 10 feet in the air. at least, thats what happened when my chem teacher did it. the janitor was pretty pissed that he had to clean the ceiling after that one.
alternately, you could just offer someone a coke while theyre eating several mentos :)
Refer them to this site, or print off some choice pages and hand it out in class. Ask them what they think they should do about educating the public... etc.
Then you can show them this site.
After that, you can tell them that gullible is no longer in the dictionary. Hope that there aren't any who hesitate and look around before rolling their eyes and groaning.
-eg
Sounds like a great way to take a core sample of your thumb too...
-- ;-)
Kuro5hin.org: where the good times never end.
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. I don't question his memory... I think his teacher activated the emergency sprinkler system...
Who moderates the meta-moderators?
Anyway, cool experiments using a microwave oven, of course, include the grape experiment (leading to ball lightning, preferably), and the actual microwaved ball lightning experiments.
Also be sure to check out some of these other ones. I especially like the soap.
Be sure that you can defend yourself against the parents, though, as they will likely not be very pleased, and will want to rip your lungs out, or some such mischief.
Have a ball (lightning).
Please clarify "plasma balls" and "between legs".
Oh, come on, isn't there some kind of Darwin Honorable Mention that we can give him? Lord knows he deserves it....
Yes, I have a big yellow pin-on button for him that says "Me Stupid".
Table-ized A.I.
In college, the TA running a physics lab on instrumentation had an amusing sense of humor. The day we did the thermocouple experiment (measuring the resistance of a thermocouple in water of various temperatures from freezing to boiling, and in liquid nitrogen), he showed us the 'proper' way to dispose of the liquid nitrogen (each of us having about four ounces in a styrofoam cup) -- you go out into the hall, and listen at other doors to determine which ones have lectures going on, then make a standard bowling delivery at the door, shooting the contents of the cup under the bottom of the door. The liquid nitrogen evaporates almost instantly upon hitting the floor, so all that happens is a cloud of fog suddenly billowing under the door.
The professors apparently were long familiar with these disposals, because we never heard one of them miss a beat on their lectures. However, if you could catch a Freshman Physics class, who'd never been exposed to the joke, the shrieks were amazing to hear.