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.

Comments

Baking soda and vinegar

[npietraniec]

Anything that explodes is cool. Baking soda and vinegar, Sodium and water, Magnesium and fire, drano and tinfoil... :)

Re:Baking soda and vinegar

[Anonymous Coward]

Well, that's really nothing to boast about. [cnn.com]

In no way am I condoning the actions of the stop-sign thieves, but if you steal a stop sign, you should get the punishment that is on the books for STEALING A STOP SIGN. Where I live, after about 11:00PM the trafic lights at most of the intersetions around my suburbish town go into a mode where they just blink yellow. What does that mean? Well, I thought it was common knowledge if you took a driving class that ALL INTERSECTIONS are inherently dangerous and the yellow lights are a reminder to PROCEED WITH CAUTION. I don't need a stop sign to remind me an intersection is dangerous, and quite frequently I DO stop at places there SHOULD be one before making sure it is safe to proceed.

Yes, it was terrible those people were killed in an accident. Would their lives have been saved if the stop sign was still standing? Maybe. People DO run and ignore stop signs. Would their lives have been saved if they approached EVERY intersection with caution? Yes.

I can't wait for the day they start prosecuting the gun manufacturers because guns are used in killings. I think it'll come shortly after the RIAA shuts down the P2P networks for contributory infringement.

My personal favorite

[Boglin]

My favorite was always the standing fire wave. First, take a metal pipe and cap both ends. Drill hole at even intervals along the end of the pipe. Cap both ends, but put a speaker on one end. Also, attach a nozzle where you can pump gas into the pipe. For the show, hook the gas line up to the nozzle and turn it on. Next, set a fire on the gas coming out of each hole. You should get a series of flames of even height. Now turn on the speaker and hook it up to source with a constant frequency. If you set the frequency to one of the resonant frequencies of the tube, you should see the flames forming a wave. (Please note, I am just trying to recall how this was done from memory. I may have left out some crucial step that stops this from just being one big pipe bomb. Don't try this at home unless you are sure of what you are doing.)

Re:Hot Wax

[pizza_milkshake]

a science teacher of mine did this when i was in high school... it was probably the coolest demo i ever saw :) the "put the rose in the liquid nitrogen and then break it" was kinda cool but he didn't put it in long enough...

Stab a Paper straw through a raw potato

[cyber_rigger]

If you put you thumb over the end of a paper (or plastic) straw
you can jab it through a raw potato like a dagger.

Sealing the end allows the air pressure to build up and make the straw super rigid.

Re:Aluminum pipe and magnets.

[EvanED]

This has added value if you mention that (at least according to the physics teacher I had...) Kennywood Park uses this method to break the fall of the Pit Fall (take you up 300 ft (if my memory stands; it very well may not) and drop you).

Discrepant Event

[AlphaBrav]

What you are looking for is a discrepant event. There are plenty of archives of neat (and safe) discrepant events on the net, just hit a search engine.

Re:Boiling water 'til it freezes!

[kwerle]

I guess I was asking for that
lalala
15 seconds... :-)

Re:Momentum, actually

[King_TJ]

Um, not only that - but each ball in the "stack" has to be considerably more massive than the one directly above it.

Sure, for a demo with only 2, a basketball and tennis ball do the trick. For 3, you could probably use a ping-pong ball as the 3rd. one.

You quickly reach a point where you run out of useful objects though. With 20, what's the size of your ball on the bottom? A small meteorite?

tin foil

[Anonymous Coward]

is apparently pretty hard to find. Even McMaster-Carr (industrial supplier, with a huge variety) didn't have any.
Aluminum foil is another story.

Are these demos effective?

[Goonie]

This is slightly OT, but I've always wondered about how effective these shows are in getting kids interested in science. Sure, they enjoy them greatly when they go, but do they actually care about why all this is happening, and how people figured out all this stuff?

How do you get people enthused about the actual process of science - coming up with hypotheses, figuring out how to test them, analysing the results, and so on?

Re:Liquid Nitrogen Ice cream

[octalgirl]

Well, the guys are on board today! Almost every post has something to do with blowing things up! These are kids - do we really want to send them away with the message that science is all about creating explosive devices at home?

And what about girls? They really are not interested in the destructive side of things. I like this ice cream one. Everyone likes ice cream. Parents won't freak out when their kids come home with a new way to make a snack, but watching Junior shoot a can across the living room is sure to rile them. Or how about something from CSI? Forensic science is becoming extremely popular and many public schools are beginning to integrate it into their curriculum.