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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.
Anything that explodes is cool. Baking soda and vinegar, Sodium and water, Magnesium and fire, drano and tinfoil... :)
Put some sugar (white cane) 1/4 full into a test tube. Pour on sulphuric acid to 1/2 full. Wait for a 1-2 minutes and watch the carbon rod emerge from the test tube amidst smoke!
It's funny to watch.
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
Get some milk, some cream, some sugar, some vanilla, and any other candies you may want to add, mix it with LN2 until it's frozen, and eat!!! "Steams" a lot (the steam is actually frozen water vapor). Directions here Yum!
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
Get a petri dish, a plate magnet, a superconductor, and some liquid nitrogen. Put the petri dish on top of the plate magnet, and the superconductor inside the petri dish. Slowly pour in the liquid nitrogen. When the superconductor reaches superconductivity, it'll float.
(or do something along those lines...)
~A'Ëq'i4d)^'$ÊSÈòB
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.)
Find free books.
(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).
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.)
The book is chock full of science-geekly fun. The demonstrations are clear and exciting. Kids will love them. The accompanying explanations are in-depth. If you do them all and learn why they work, you'll soak up a fair amount of physics.
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 American Chemical Society (ACS.org) and affiliated sections are full of resources for this sort of thing. Every year they put on a big program called National Chemistry Week'. The National Academy of Sciences (nas.edu, nationalacademies.org) has outreach programs as well.
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.
Or you could stick some flys in a microwave. They live because their bodys are to small to absorb the radiation. This one really needs a kitten to set up with though....
"A language that doesn't affect the way you think about programming, is not worth knowing" - Alan Perlis
Many years ago, I did a couple of science programs as part of a science after-school program at a downtown middle school.
First one was chemistry. Did a mixture of hands on plus some interesting demos. Hands on was stuff that was designed to be SAFE - indicators, baking soda and vinegar, etc. Demos were designed to be visually interesting. Burning magnesium, volcano (ignite ammonium dichromate), thermite, fun with liquid nitrogen. (Keep the kids WELL BACK for these). The kids loved it.
Second one was on crypto - simple encoding, decoding, and cryptanalysis (breaking caesar cipher by brute force, and substitution cipher by letter frequency analysis). Kids were divided into teams of four for a set of exercises. One of the teachers told me the kids were passing encoded messages in class for weeks afterwards.
Make sure the kids have fun AND learn something and you'll be successful. Good luck.
[Insert pithy quote here]
but when I was in 6th grade, I did a magic show with chemistry stuff...my dad was a chemistry teacher in high school and gave me some salts....I forget what exactly they were potasium and some other kind. any way, I labled it as turning 2 solids into a liquid.....the kids seemed to be impressed, though I found out the hard way that it made amonea or an amonea type substance.
it was pretty cool.
I am the Alpha and the Omega-3
Boiling water in a paper cup: the cup must not be coated with wax, it works because paper burns at 451 F, and water boils at 212 F. Just keep the flames low enough that the rim of the cup doesn't light up.
Crushing cans: There are several variants, but the cheapest one involves putting some water in the bottom of an otherwise empty soda can. Boil the water until you see steam coming out. Then, quickly tip the can over in to about an inch or two of cool water.
Mag-Lev: find an aluminum pot lid. Everyone knows that aluminum isn't magnetic, right? Well, rig up the lid so that it's attached to a drill. Take a small disk magnet (rare earth works best) and attach it to an armature (easiest way is to take some sort of steel latch or hinge and just stick the magnet to it). Spin up the lid, and hold the magnet over it with the armature. The key is that if it weren't for the mag lev effect, it would fall on to the pot lid.
Angular momentum: Student + weights they can hold + disk they can sit on and spin = good fun. Show them how pulling the masses is speeds them up, and holding them out slows them down.
There's a whole lot more, but that's all I can think of right now.
BlackGriffen
I suspect that what you saw was a bill doused in off-the-shelf rubbing alcohol, which is basically methanol diluted with water. Soak the bill and light it; the alcohol will burn off, and the water remaining behind will keep the bill cool enough to avoid charring. A distantly related demo involves boiling water in a paper cup over a fierce fire... it's most dramatic in a roaring fireplace, but a bunsen burner ought to be good for a laugh, too. The water keeps the paper cup cool enough (100 C, of course) to avoid burning.
--Larry
Never attribute to malice that which is adequately explained by incompetence
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.
One of the more surprising experiments I rememberd from high school where the teacher took two perfectly clear liquids--water, for all we know--an poured them together. They instantly turned a bright, fire-hydrant yellow. There were gasps all around the room.
I don't remember what the two substances were, but I seem to recall that one was lead-based and the lead combined with something else to form the precipitate (it later settled to the bottom, I think).
I'm sure any competent chemist, especially one in the paint industry, should be able to point you in the right direction for something like this.
My personal favorite experiments are those where I personally confirmed some fundamental property of nature. I've ``proven'' that absolute zero is about minues three-fifty Fahrenheit; distinguished lead shot from iron shot from tin shot by calculating their specific heat; and measured the speed of sound using a tuning fork.
Don't just tell the kids some fact. Give them the chance to prove it for themselves.
Cheers,
b&
All but God can prove this sentence true.
>>Just have a vat of liquid nitogen, put in something (a rose for example), remove it and shatter it by throwing it on the floor (or use a hammer). Fun experiment, and looks impressive with the fumes of the liquid nitrogen ;-)
Racquet balls work very well. Start the demonstration with them: start playing with a normal one. Someone takes it, dunks it in LN2, and starts playing again...
>>I wouldn't try the hand-in-boiling-lead anytime soon. Back when I was a kid, I made figures out of lead and I got some nice burns because of that. Lead splatting on your hands is not fun, and the Leidenfrost experiment didn't really help.
It's one of those "very impressive if you can do it but very dangerous if you can't" experiments.
Take a tennis ball and a basketball. Bounce each separately in front of the kids. The place the tennis ball on top of the basketball and drop both. If you do it right, so the two are in contact when the basketball hits the floor, it will definitely shock them. The basketball will hardly bounce as its kinetic energy is transfered to the tennis ball. The tennis ball will shoot up into the air as if fired from a cannon! Be sure to have lots of head room for this one.
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.
Back in college we (the Society of Physics Students) would have a demonstration of stupid physics tricks. Try some:
1 - Spewing liquid nitrogen. WARNING: I've done this but if you screw it up it is your own fault and will HURT YOU. It is possible to take a mouthful of LN2 then immediately spray it back out in an impressive cloud of vapor. This works because a tiny layer of LN2 vaporizes when it hits your tongue, thereby insulating you from the LN2. This effect is very short-lived and you can FROSTBITE YOUR TONGUE if you don't immediately spew it back out!!!
2 -- Balloons in a trash can. Put 1 inch of LN2 in the bottom of a trash can (you *might* get this to work with dry ice -- easier to come by). Ask the audience to guess how many balloons will fit in the trash can (don't let them see the LN2!)Begin dropping balloons into the trash can. The balloons will shrink to a fraction of their room temp size as they cool down. Think "clowns in a car" for geeks.
3 -- Bed of Nails. I've lain on a bed of nails built out of heavy plywood and standard nails. This takes work to build: the nails MUST all stick out exactly the same distance through the wood, and you should remove any burrs or extremely sharp tips. I *believe* we used nails on a 1 inch grid (which was overkill for safety). USE A PILLOW! Your head is heavy and ROUNDED -- it will end up supported on only about 4 nails: NOT ENOUGH. You may want to do a little research to get the optimal grid size "nailed down".
4 -- Corn starch solution: Cool stuff. Under pressure a thick corn starch solution will act like a solid. Without pressure it is a liquid. Fill a pan with it, demonstrate that it flows, then (with viewers gathered around) slap your hand into it hard. They'll expect a splash that never comes. This works because corn starch is a long molecule that curls under pressure, interlocking the molecules into a "pseudo-solid". Throw it back and forth like a ball. Don't pause, though: the impact with your hand will keep it solid only for a second before it "melts" again!
5 -- Get a large piece of Transparent Aluminum, a sonic screwdriver, and a tribble.
Actually, that one tends to offend squemish members of the audience, so we'll skip it here...
Life is short: void the warranty.
- 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
I recommend Vacuum Bazookas, Electric Rainbow Jelly, and 27 Other Saturday Science Projects. Loads of fun things to do, and each project includes a section for the science behind the project, which will allow you to get as in-depth as you want.
www.scifun.org is a good website oriented toward experiments that can be performed with household items. There's also a TV show that corresponds to the website that has been playing nightly on PBS (in the Seattle area, anyway).
Let's try not to let fact interfere with our speculation here, OK?
Also, try goobleck. It's a cornstarch based substance that behaves as a solid or a liquid. Water is the other ingredient, but I don't remember the ratio.
It's actually called "ooblech," not "gooblech," but what you're talking about is what you call a "non-Newtonian fluid." Technically, a non-Newtonian fluid is one whose viscosity is not constant for all shear rates. There are two types of non-Newtonian fluids: rheopectic and thixotropic. The viscosity of rheopectic fluids increases with increasing force; in other words, the harder you smack them, the stiffer they get. Thixotropic fluids are the opposite; their viscosity decreases as the amount of force applied increases.
If you read much science fiction, you'll inevitably run across the idea of liquid armor, sometimes called "armorgel" in the books. The basic premise is that you could cover vulnerable parts of your body-- like your torso, or your elbows-- with a garment that incorporates pockets filled with rheopectic fluid. As you move around, it feels like these little pockets have water in them, but when something dramatic happens-- like getting shot, or cracking your elbow on the tarmac-- the fluid hardens to absorb some of the force and to protect you. It's a fairly common idea, and one that's not totally far-fetched.
The suspension of cornstarch in water forms a rheopectic fluid. It looks and acts like a liquid when it's inert, but when subjected to force, it changes is viscosity pretty dramatically. For example, you can take a handful of cornstarch-water liquid and pass it from hand to hand rapidly. While you're doing it, it feels like it has the approximate consistency of silly putty or bread dough. As soon as you stop moving it, the viscosity drops drastically and it runs through your fingers.
Another fun demonstration is to take a moderate amount of cornstarch-water suspension-- say, 500 ml or so-- and pour it from a height of about five feet onto a tile floor. The fluid will pour like water, but when it hits the floor, it'll bounce like dough or putty. After a bounce, or two if you're really lucky, the mass will return to its liquid state and go all puddly.
Thixotropic fluids are more common and less interesting, because they're very thick when at rest, but grow thinner when subjected to force. The most common thixotropic fluid is ordinary tomato ketchup.
I write in my journal
Chemical Magic - 2nd edition
L.A.Ford, E.W.Grundmeier (Designer)
Dover Pubications (August 1993)
ISBN: 0486676285
There is one that's especially good for Halloween, where it starts out whit, and after about a 20 second delay, turns orange, and then another 20 seconds or so, turns black. It's a Potassium dichromate experiment that's pretty cool (it's an endothermic reastion that causes the color change for yellow (hidden in the white) through orange, to black (a dark blue/black).
You may also want to look at:
http://scifun.chem.wisc.edu/demoser.html
And:
Chemical Demonstrations - A Sourcebook for Teachers - 2nd edition
L.R.Summerlin, J.L.Ealy Jr.
Amer.Chem.Soc. (1988)
ISBN 0-8412-1481-6 (v1), 0-8412-1535-9 (v2)
-- Terry
To do this, put some sugar in a beaker under a fume hood and use tongs to pour a bit of concentrated sulphuric acid on it from a second beaker. The acid catalyzes water extraction from the sugar (which is exothermic), giving you a big mass of carbon puffed up with steam. This sponge is much larger than the original sugar sample (demo looks coolest if this greatly overflows the beaker; you get a column of carbon coming out of it).
Handle the acid with great respect, as it'll eat through anything organic or metallic. Phosphoric acid probably works for this too, though I haven't seen it done.
Inflate a balloon, tie a string to it, and then lower it into a dewar of liquid nitrogen. As the balloon approaches the nitrogen, the air nearest it cools and becomes a lot more compact (remember gas laws). What you end up with is something that looks like a deflated balloon, with either very cold air or (if you dunked it) liquid oxygen and nitrogen in it. Leave it on a counter, and it may re-inflate (try not to freeze all of the rubber if you want it to do this).
Dip just about anything containing water into liquid nitrogen, and it turns into a rock. Do this with something fragile, like a flower, and you get a flower that shatters as if it was made of glass when you tap it on a desk. This is very impressive.
I've heard of someone dunking a banana and shattering it with a hammer, but you'd have to leave it in for quite a while to make sure it's good and cold. When I tried similar things, the ice deformed instead of shattering.
This one only works if you have a high-powered laser handy. I suppose in a pinch a sufficiently powerful ordinary light source would do too. Stick a coloured balloon inside a transparent one, inflate the inner balloon half way, tie it off, and then inflate the outer balloon fully. You end up with a coloured balloon inside a transparent one. Shine a laser or other very bright, localized light through the balloons and the coloured balloon will have a hole melted in it and pop, leaving the transparent balloon intact.
This was a fun demo put on by the local science centre. I suppose you could use a fresnel lens to focus sunlight down, but a) that's cheating and b) that works by a different method (the hot spot is only at the focal point).
Do do this demo, mount a speaker and a microphone next to a target. For best results, use a directional mic and the mic/target line at right angles to the speaker/target line (i.e. pick up sound from the target, not the speaker). Place an object prone to vibration (like a wine glass or other drinking glass) in the target zone, turn on your amp, and tap the glass's rim. It will shatter very shortly.
Get a glass or plastic tube, fill it a third full of water, seal the ends in a way that's waterproof, and lay it on its side. Put a speaker at one end, and hook up a signal generator to an amp to feed the speaker. Feed it with a sine wave and vary the range from about 1-10 kHz. When the frequency matches one of the resonant frequencies of the air channel in the tube, water "walls" will form at the antinodes due to the pressure vibration at the nodes exerts on the surface of the water.
I suppose if you turned the power up sufficiently you could get the same thing happening in a tilted or even vertical tube, but this would get quite loud and possibly dangerous (if you hit a resonant frequency of part of your support frame, vibration could damage a tube made of glass).
Fill beakers or glasses with coloured water (or kool-aid), and then either drop in a pellet of dry ice or pour on a couple of teaspoons of liquid nitrogen. Both will sit on a vapour cushion on top of the water for quite a while, and the cold will make dense fog on top of the water. Instant mist-boiling potion.
If you decide to drink this, use dry ice instead of liquid nitrogen, and blow out when you sip so the pellet drifts away from you. Better yet, don't drink from it at all. Frostbite isn't fun.
This is a fun and safe demo, but needs to be done in a fume hood due to fumes and sparks. Set up a retort stand holding two or three small cans. Cut the tops off of the cans, and fill them half full of sand. Line up the cans over each other, and put a patio stone or similar large flat slab of stone or concrete under the retort. Put a large can filled with sand on top of the stone, under the bottommost can. Over the topmost can put a ring stand with a piece of steel mesh you don't mind losing. Put a piece of paper or tissue on top of this, and put a small pile of thermite powder on the paper. Put on a leather gauntlet, and use a firework sparkler to touch off the thermite (ignition temperature is higher than an ordinary flame provides, a burner flame may detonate the pile, and a sparkler is safer than a powder trail of something easier to ignite). Optionally, put a small amount of something more sensitive on top of the thermite and light that with a burning wooden splint, but a sparkler is both simpler and safer.
NOTE: Do this with the fume hood down most of the way, and for safest results put a blast shield in front of the retort stand. There will be many, many sparks thrown by this demo.
The thermite will burn very brightly yellow-white, and will throw sparks everywhere and give off vapours (probably either water from the paper, or boiling iron oxide that wasn't consumed; I haven't checked). The thermite will burn the paper almost instantly, dumping white-hot molten iron through the rapidly disintegrating screen, through the sand in each can, through the bottom of each can, and down to the large can of sand at the bottom of the retort stand. It may eat through the bottom of this, but at worst will just slightly etch the stone (the stone won't react catastrophically with molten iron, and has enough heat capacity that you certainly won't melt through it and is thick enough that it won't crack through from heat shock).
This demo is quite safe, with proper precautions, and very impressive.
Lastly, things not to do. This is not an exhaustive list:
If done right, this can be safe, as water boiling off your hand forms a vapour cushion briefly. This is easy to screw up, and has drastic consequences if anything goes wrong. Don't do it.
This can also be done safely if done right, for the same reason - the dry ice or liquid nitrogen boils, forming an insulating vapour cushion. Briefly. If you hold it too long, or are just unlucky, you get a very painful and inconvenient case of frostbite, or worse. Don't do this.
I've heard of people drinking small amounts of liquid nitrogen. This is beyond stupid.
Protective gear is a must too, but even without it, a spark or a splash will only hurt _you_. Hurting your audience must be avoided at all costs.
Have fun.
Do a fourth with 2 parts Hyrdrogen 1 part oxygen it will be about 5 times bigger than the oxygen one (once demonstrated by ISU's SCUM club)
Sigs? We don't need no stinking sigs!
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.
Get a bucket of water, drop a coin in it and run an electric current through it (my father did this with an old telephone-bell-generator). The moment you put your fingers in the water your muscles start to shake and you hardly can get them deeper in it.
bash$
Fill a funnel with sawdust and attach a hose to the end. Blow the sawdust out towards a flame and get a huge fireball.
Whats really amazing is watching a railcar do the same thing (for petroleum products).
My dad saw the aftermath, the guys pressure washed it inside and out, then closed it. >crunch.
Rather expensive though.
Put a half-inch or so of ordinary white sugar in a small beaker and add some *fuming* sulfuric acid. I have no idea of the quantities. Over the next minute or so it turns orange, then begins to smoke and bubble, then turns black as the carbon is stripped out. The carbon is then pushed upward by more carbon, rising straight up out of the beaker to a height of 6 inches or so, like a cylinder of black rock.
The way I saw this demonstrated was in a short film produced by one of my high school classmates. All you saw was the torsos of two guys at a chem lab table, measuring and pouring things, as one of them talked about his dinner at a middle eastern restaurant the night before. As he got to the part where the belly dancer came up to his table, the bubbling and steaming got going. When she started shaking her body in his face the carbon was rising out of the beaker...
Classic.
I love gravity experiments, and the "Monkey and the Hunter" experiment is by far my favorite. If I'm shooting a monkey hanging onto a tree, would it be in the monkey's best interest to continue holding onto the branch, or to let go? One would think, let go. But because gravity effects the bullet the same amount as it effects the monkey (save air resistance, but that's why we're using Physics air ;)), letting go will actually increase the chance of a hit.
Another gravity favorite shows the previous result in a slightly different setting. Take a bunch of balls with different weights but equal friction coefficient. Then take a "Pine Wood Derby"-esque ramp and race the balls to the bottom. My brother did this experiment in elementary school, and he was quite suprised to see that the time it took for balls to reah the bottom was independent of weight.
Matt Fahrenbacher
James Tiberius Kirk: "Spock, the women on your planet are logical. No other planet in the galaxy can make that claim."
I can't remember the exact details of this one, but...
I had an instructor who took a paint can with the lid attached. There was a hole in the middle of the lid, and a hole on the side of the can at the bottom. He used the bottom hole to pump the can fill of methane, then lit a match at the top hole where a small flame appeared.
He then continued to lecture as the methane in the can burned, rising in the can and being replaced by air coming in through the side hole.
Everyone had pretty much forgotten about it when the last bit of methane burned out and the flame dipped inside the can. The explosion blew the lid to the roof of the two-story lecture hall!
The birthday paradox is suprising. It is a good example of how bad humans are at calculating probabilities.
:-)
Ask everybody in the workshop to shout out their birthday (day, not year) one at a time, and ask people to raise their hand if they have the same birthday. In a class of 30, the chance of a coincidence is 70% example, explaination.
There is a 50% chance that two people out of a group of 23 will share a birthday.
If noone shares a birthday you may look silly though
I haven't confirmed this one myself, but if it works, it's pretty cool.
1) Get an older microwave. In particular, one without a turntable.
2) Get a microwavable tray as big as possible that will still fit inside the microwave.
3) Fill the microwave with miniature marshmallows.
4) Run the microwave long enough for some of the marshmallows to brown.
5) Measure the distance between the dark mashmallow bands, and convert to meters.
6) Multiply this distance by 2 (or 4?), and then by the microwave frequency, which should be listed on the back of the microwave.
7) If my instructions are correct, you should get a number awfully close to the speed of light.
What I've been told is that the microwaves can form a standing wave. The distance between dark marshmallow bands should be the wavelength, which when multiplied by the frequency, should give you the speed of light. (c = f*w).
"You know, Hobbes, some days even my lucky rocketship underpants don't help" -- Calvin
This incidentally is (one reason) why you don't pour many chemicals (e.g. sulfuric acid) down sinks...
The most impressive physics demo I've ever seen was with a motor gyroscope. It's quite small in size but it's got a low friction very dense heavy rotor inside (about 10 lbs) which can spin up to very high rpms. It's got two convinient handles along its axis. It is first connected to the outlet and is spun. After it's spining rapidly you cannot change the direction of its axis even when you pick it up in the air and even with two people trying. It's spooky. Imagine picking up a small 10lbs dumbbell and not being able to turn in any way with some invisible force preventing you whichever way you push it!
This one required quite a bit of work, but you have it forever once you've done it ...
... you die ..."
Make a bed of nails. Probably 50x150, with nails every half-inch or so on a backing of double-thick plywood. You set the stage by taking off your shirt, so it's guaranteed to get attention. Then you simply lay down. This demonstrates how mass can be distributed in a way that no one nail is supporting enough weight to break skin.
My physics teacher in high school did this one, and it has stuck with me lo these many years later.
When he was showing us formulas and equations and such, he always couched them in terms of a person in peril -- standing at the top of a cliff, being whirled around by angular momentum or whatever. The solution to the equation was always accompanied by "And then
All of these lessons have stuck with me far better than my junior-year chemistry lessons, for which the teacher left the class to make soup (don't ask) and drink liquor in the lab and told us to learn it from the book.
My high school chem teacher did the thermite reaction. There's now a small bead of iron imbedded in the table which missed the beaker of water and sand (works well; water has a high specific heat, and the sand will keep the falling iron from breaking the glass) underneath.
Really dry white flour works, too... Must be very careful, though. The larger the cloud, the larger the fireball.
The two metals are Aluminum and Iron Oxide. See the post "Thermite and Gas Ballons" for more details of how to set this one up. (That description has a slightly different method of triggering the reaction.)
peek at this site for ideas:
p he re.pdf
http://stanley.chem.lsu.edu/webpub/demo-1-atmos
"There are 11 kinds of people: those who know binary, those who don't, and those who could not care less!"
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.
I strongly doubt that any methanol is sold as rubbing alcohol anymore in any civilized country. It takes a decent amount to kill, but not much to permanently blind.
Usually people use isopropanol.
I Can't Believe It's A Law Firm, LLP does not necessarily endorse the contents of this message.
it was cool at the time i swear
I want 2D games back.
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.
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.
OK, when I was in maybe 10th grade, I went to some sort of statewide science symposium. Of course, the first night, we had a professor give a talk that included a lot of exactly these sorts of graphic examples of chemistry and physics for entertainment.
The big show stopper at the end of his lecture was amazing. There was some sort of chemical reaction - I have no memory of the reaction whatsoever, but he went through it fully on the blackboard beforehand. It had a metal reaction chamber, manufactured such that it made a quiet whistle as the reaction went on - must have been the evolution of gases. Perhaps there was some sort of glow or light as well. He asked that everybody (hundreds of us in the lecture hall) be very quiet, and they turned off the lights as well. At first not much happened, then it started to whistle, and got quieter and quieter. Everybody is sitting in suspense - you could hear a pin drop other than the whistle.
When the whistle was almost inaudible (which meant that the reaction had run to completion) there was some other combination that occurred. With the result of an incredibly, mind-shatteringly loud and unexpected BANG accompanied by a powerful flash of light. I clearly remember seeing the professor's grinning face in the flash.
Whatever it was, it was great. Didn't convince me to be a chemist, but surely made me think about it.
Anybody know what this was? It seems like this might have been something that was separating hydrogen and oxygen from water, then explosively recombining. Or perhaps it was something about activation energy - the original solution decomposes into stable components until the original material isn't present anymore, then the temp climbs and kapow!
David Fung
By shining a strobe lamp in the darkness onto a fan and varying the strobe frequency you can make it appear to smoothly stop rotating or even make it rotate backwards!
Place two identical tuning forks close by. Hit one and it will start humming. Then silence it with your hand and you'll notice that the one you did not touch is humming too (because of the resonance)
Take a 2 liter empty pop bottle (plastic!). Drill a 1/4 inch hole in the cap. Pour about a spoonful of alcohol (eg rubbing alcohol -- it has to be concentrated enough to burn) into the bottle, swirl around, and dump out the excess. Put the cap (with hole) on the bottle and carefully hold a flame to the hole.
If you get the fuel-air mixture right (this may take some practise) the rocket will launch itself a good 10 feet or so vertically, maybe 20 or 30 foot range if launched at an angle.
I've never seen one of these burst (those bottles ought to hold over 100 psi), but you never know -- you might have a defective bottle. And you are playing with fire. Beware bursting and fire hazards.
(Or, in the words of the motto of the Denver Mad Scientists Club, "sumus scientes, noli hic domi temptare" (we're scientists, don't try this at home).)
-- Alastair
Potassium Permanganate?
It's dark purple, and is rather impressive when mixed with glycerin...
Hey, he may not get the Nobel, but for sure he can acheive the Darwin.
That's why you *never* pour organics down the drain. Ever. Aside from being illegal as hell. Get a big jar, and pour all the organics into that and dispose of them properly.
BTW, unless you have a license, you're not allowed to dispose of acid by neutralizing it with a base and pouring that down the sink. Always remember to make that part of the experiment, otherwise you need a treatment permit.
It might open one or two students' minds to some of the notions of finite math and calculus, which would be a bonus. Plenty of opportunities to use a simple spreadsheet model to calculate the kinetic energy from the final stage.
Most students would benefit from a practical analysis of Newton's Laws of Motion, and this is an excellent opportunity to relate mathematics to the visceral impact of ball bearings shooting through 2x4's.
Don't forget to film it for later analysis and instant replays, as you probably don't want to be shooting high-velocity projectiles in close proximity to the students very often.
Back in the 1980's, when I was a Physics grad student at Rensselaer Polytechnic Instutute in Troy, NY, there was a tradition of putting on physics "Magic Shows" for the freshman classes. A few dramatic classics included these:
Make liquid oxygen by passing air through a coil of copper tubing immersed in a bath of liquid nitrogen (oxygen boils at a higher temperature than nitrogen). Great care is needed in working with LOX, it makes the damnest things catch fire!!!
Dip a cotton ball on the end of the proverbial 10 foot pole into liquid oxygen, wave it over a safely-distant flame, and create a BIG orange fireball.
Demonstrate that liquid oxygen is paramagnetic (weakly attracted to magnetic fields) by taking a BIG electromagnet with a small gap, placing a small test tube of LOX below the gap, firing a high DC current through the magnet, and video-watching the LOX being sucked up into the magnet gap.
With thanks to the late Professor Harry Meiners, otherwise a difficult person to work with, but a great showman...
"My strength is as the strength of ten men, for I am wired to the eyeballs on espresso."
I've always been impressed by clock reactions. This time of year, if you can get an orange/black one going for halloween it would be perfect:
p us_a/woodlandm/Demo1.html
http://www.mun.ca/educ/ed4361/virtual_academy/cam
Draw some tap water into a large beaker with some ice cubes, take a
big sip, then stick it under a glass dome and crank down the pressure
until you can get it to a nice rolling boil without melting the ice.
You can impress people of all ages with that one. The trouble will
be in convincing them it's science, as opposed to magic.
Cut that out, or I will ship you to Norilsk in a box.
We first lit some candles in small aluminum candle holders (cupcake baking foils) and watched the candle get smaller as it burned and saw the light coming out coming and felt the heat. So I formulated the hypothesis that wax must have a substance in it that is given off as heat when it burns. The candle gets smaller, the heat and light come off. Obvious.
So I suggested that we capture this stuff, lets call it phlogisten, a name I suggested that Priestley had used for the substance.
We could catch it in a jar by putting the candle in a the aluminum cupcake holders, floating the foil in water in a saucepan and putting a jar over it. As the phlogisten came out of the candle it would go into the air pushing the water down and so we could measure how much was given off.
Nice scientific experiment. Obvious hypthosesis, easy and cheap experiment, expected result. If you know the actual result, you have a wonderful way to show that one needs experiments as well as theory to further science.
I still remember this demonstration from the Museum of Science and Industry when I was about 8 years old...
It was a large box with pegs, and a hole at the center, top. The balls would fall through the hole, down the pages, and land into slots at the bottom. On the front glass was a bell curve painted on the glass.
I watched in amazement as time after time, the balls would fall into the shape of the bell curve, even though they were falling randomly.
Sometimes it's best to just let stupid people be stupid.
My neighbors are doing a "Science Can Be Fun" demo for some schoolkids (they work at NCAR in Boulder) and the project for this year is making french fries.
PVC pipes and fittings (including a large-handled valve for a trigger) are all available from the hardware store. The racquet was a few bucks at a thrift store, and they plan to spray fries (raw, but still) over the heads of the kids.
The lesson is simple -- stay in school and someday you'll get paid to make projectile weapons in your garage.
Or maybe it's PV=nRT. I forget.
I have a friend that demo'd this to some students- they stirred the mixture with a glass rod- unfortunately the shear increase was far greater than they expected (even during their tests for some reason) and the rod snapped into 3 pieces- 2 of which lacerated and punctured her hand quite severely.
Be careful on ANY demonstration that you have not rehearesed completely, and, as corny as this sounds (no pun intended), hold a 'review' session with your peers to make sure you have considered all things that could go wrong.
Fill a balloon with propane. light it... Note that you don't get an explosion... just a fireball.. Burns at the interface of air/propane. Fill second balloon with oxygen/air. Add propane... Do the same thing (I forget the proportions... I think it's 1 Oxygen to 2 propane). Note an actual EXPLOSION because gasses are pre-mixed. This is a good intro to the mathematics of explosives (and things like why car gas tanks don't usually explode like in the movies)
Free Software: Like love, it grows best when given away.
(or, for the extreme crowd, demonstrating the Leidenfrost effect by sticking one's hand into a vat of molten lead [PDF])
You could top that by chopping off your head and blinking your eyes.
Don't know about sulfur hexafluoride, but I can tell you FOR SURE that nitrous oxide (NO2) will do the same thing.
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'm not very good with chemistry but here's two that I thought were neat.
1) Fill fish tank with water.
2) Put rosen on the surface of the tank.
3) Put hand in the tank.
4) Observe that as you pull your hand out of the water it's totally dry.
1) Fill glass with ice.
2) Fill same glass the rest of the way with water.
3) Observe that the ice is sticking above the rim of the glass and the water is up to the very rim.
4) As ice melts, the water level doesn't change *at all*. The amount that the ice sticks out is equal to the the amount that water expanded as it turned to ice.
Vanguard
That which does not kill me only makes me whinier
Steam crushing a can-
Hold a soda can with a little water in it in some tongs. Heat it up over a bunsen burner or similar so the can is full of steam. Then place it mouth end down in a plate of water. The temperatre will drop, and PV=nRT will crush the can in a fraction of a second.
Barbells and an office chair.
Not too difficult- sit in the chair, hold the barbells (or even just your arms and legs out), get them to spin you up, then pull the weight in to increase angular velocity. Just don't puke.
Baloon in a car
You'll probably have to videotape this unless you can fit everyone in a vehicle with good acceleration and cornering. Anyways, get a helium baloon, hold it in the most spacious area of the car, and subject the car to acceleration. Floor it, hit the breaks, take some corners at speed. Maybe some steep climbs or drops if you're adventurous. (Don't try this on a busy street). When you're getting pressed back into your seat as the car speeds up, the baloon is going forward. When you take a hard right and get pressed up against the door on your left, the baloon leans right. Basically, it's 'anti-acceleration' in the same way that it's 'anty-gravity'.
When my physics prof asked the class to think about this and tell him what the baloon would do, the only person to get it right was my friend who was being a jackass and trying to give the obviously wrong answer.
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)
The Coolest Physiscs Experiment that I have ever seen is as follows.
You'll need the following:
1) An old oildrum or other large steel drum that has a tight sealing lid.
2) A large CO2 filled fire extinguisher
3) 2 gallons of boiling water
4) A Ballpean hammer
5) Spectators
Here's how to do it:
1) Place the drum outside in a field or a nice clearing.
2) Boil the water (rolling boil)
3) Pour the boiling water into the drum, set the lid on loosly, wait about 45 seconds and then seal the lid.
4) Start hosing down the drum throughly with the fire extinguisher.
5) when you've expended the entire fire extingusher take the ballpean hammer and give the side of the drum a good whack.
6) Jump Back
If your drum seals well it should with an awesome whooshing sounds just collapse and flatten out. You pbly should have the kids stand back a bit and definitly need to waer safety glasses and overalls (scalding water flys if you do it wrong). Very impressive and tons of fun!
Rule of Life Number 2: Remember, it can all go to hell at any minute. --Jimmy Buffet
Take a strong glass tube with one open end, about 12" long and 1/4" inside diameter. Place a small piece of cotton ball in the tube. Press a plunger with a 1/4" rubber stopper on the end into the tube, hard. When the air pressure gets high enough, enough heat is generated to spontaneously combust the cotton with a small flash (think diesel engine).
acutally you induce a magentic feild with an electric current, you pass an electric current though a conductive material and a magentic feild is prodduced, and vice versa, try this, get a multi-meter and hook both leads together, then pass a magnet rapidly over the wire (works best if you have a horseshoe mageitc, and rapidly move the wire up and down thru the middle of the horsshoe magnet) if you have a strong enough maget, or sensitive enough meter, you should see readings on the meter, an analog meter works best in showing the effect. that same principal is at work here, except in reverse.
Sun is Warm, Grass is Green
Don't dip your hand in lead.
Don't put liquid nitrogen or dry ice in your mouth.
[etc]
I think you've just written the script for "Jackass II".
True story, and an occasion to remember for any students present should you repeat this demonstration.
... but when it's right in front of you, i'm sure it would *seem* a lot like 30 feet). At the end of this demonstration, the first five rows of bleachers had been completely cleared (into the next few rows). The first few rows remained empty for the rest of the term.
A friend of mine walked into the first lecture of his chemistry class. This particular lecture series was being held in the gymnasium of the college, with the students piled in on the bleachers down towards one end of the gym, where a small table had been set up. This tabled contained a small bunsen burner and three empty-looking 2-liter soda bottles, with their caps screwed on. As the students settled into place, the professor walked into the room, and quietly lit the bunsen burner. He then proceeded to unscrew the cap from one of the bottles, carefully placing his thumb over the opening. He turned to the class, and with no further introduction stated, simply: "This bottle contains hydrogen. It burns readily." He then took his thumb off the end of the bottle and quickly touched off the stream of pressurized gasses on the burner, and *FWOOM*. A flame somewhere on the order of 30 feet long shot out of the bottle. (or so I'm told
09
One thing my physics teacher did was to hang a rod sideways from the high ceiling of a gym by the ribbon from a cassette tape. On the rod he hung 2 garbage bags full of crumpled newspapers. Students would walk towards the bags and the gravity principles would take over and the bags would be attracted to the students. Was a good demonstration of how gravity works between 2 bodies
And then there's always the good ol' fashioned shatter stuff with liquid nitrogen. Always a crowd pleaser. One demonstration I saw at a science museum was freezing beer vs. vodka (low vs. high alcohol content) and observing how long it took, since alcohol has a lower freezing point then water
There are only 10 kinds of people in this world... those who understand binary and those who don't
My science teacher in high school did this one that I really liked:
Heat up an empty pop can over boiling water (using tongs of some sort), right side up. Then, quickly turn it upside down and plunge it into an icewater bath. It will implode with a small pop and end up almost as small as if you had stomped on it to crush it for recycling.
Don't steal. The government hates competition.
Nothing was more surprising than our surprise demo on capacitors, where a 10,000 volt capacitor was charged by the prof and discharged onto an arc of aluminum foil. Boom.
-Sean
hehehehe.
;)
HAHAHAHA
(btw that should be N2O; NO2 is poisonous)
Not really sure if the students will respect you too much after you collapse into a giggling heap on the floor after demonstrating the voice lowering effects. Then again, if you let them try it for themselves... For that matter they could make it themselves by gently heating ammonium nitrate (added bonus: heating it too quickly will cause an explosion)
Experiments with nitrous oxide may encourage students to pursue a career in dentistry
"I think it would be a good idea" Gandhi, on Western Civilisation
My high school physics teacher, once we got to the section on Newton's laws, did this every year...for real:
First he would take out a large 'Bed of Nails', a body length piece of wood with nails evenly spaced out over the wood with the pointy-sides faced upwards, and lay down on it. Then he would take another, smaller piece of wood with nails driven into it and put it on his chest, with the pointy-sides facing his chest. Then another teacher would come into the room, bringing in a **CINDER BLOCK** and put it directly on top of the nail-laden wood on top of the physics teacher's chest. Then the assistant would pull out a _Sledgehammer_ and give the cinderblock a hit with full force.
The cinderblock breaks, the physics teacher survives, and his shirt is only slightly imprinted with a grid of pointy impressions. The force of the sledgehammer's impact is completely absorbed by the cinderblock and not the teacher's body. If the cinderblock did NOT break, the teacher would receive a hundred holes in his body.
He did this every year and never received a wound. Amazing, really.
Salis
Favorite
other memorable demonstrations from 9th grade science class:
:) We tasted successively stronger acids until we got to hydrocloric acid, as I recall. I just got a slight whiff of that one, not a real good taste.
:)
put a feather in a vacuum chamber and watch it fall as fast as a rock.
fill a mason jar with pure oxygen, light a piece of steel wool (which will have a very feeble red glow where you lit it, if anything) and then put it in the pure oxygen. It lights up real good.
fill a mason jar with pure hydrogen and then open the jar and light it up. It just makes a big bang if memory serves.
(there are probably safety considerations with the last two which I'm forgetting.)
Someone already mentioned the gas can filled with boiling water which you seal and then cool it down to cause the gas can to be crushed by atmospheric pressure. That was another good one, from high school chemistry.
Also in high school chemistry we had an "acid tasting experiment" which I don't recommend you try.
There are a lot of good little science toys, I mean demonstrations, at Scientifics Online. The van de graaf generator is cool, of course. There is also a magnetic levitator which is very cool, but its scientific value is unclear.
This one was shown me by my dad, a sometimes physics prof in his retirement, when he needed to show the principles of lift as he instructed high school youth on sailplanes (gliders):
All that's required is a solid wooden spool with a single hole, and a circular piece of construction or preferably card stock paper, about 10cm in diameter.
1) Ask the kids what will happen if you blow through the spool with the disk centered on the hole on the other side, flat side toward the spool hole. (they should expect it to be blown away when you take your hand off)
2) Place your index finger onto the paper over the hole in the spool, and put the other end of the spool to your mouth.
3) Blow into the spool very hard.
4) Take your finger off the paper. The paper should stay in place. When you stop, it will fall off.
This demonstrates that swiftly-moving air has lower pressure than stationary air--hence sucking the paper to the spool by blowing.
Here's a cool (cold, actually) one: Buy 2 roughly 2lb blocks of dry ice. Scoop out a golf-ball sized hole in one of the blocks, and drop some magnesium shavings in. Ignite the shavings with a lighter/bunson burner/etc. Do not look directly at the burning Mg. It will hurt. But _do_ notice that it burns a bright white. Now put the second block of dry ice down on top of the first block so that it covers over your pit full of burning Mg strips. You'll notice that even though the Mg is now in an atmosphere of pure CO2, it continues to burn. And now it's a pretty (and much less painful) red color.
One of my favorites is the sodium acetate tower. It is a very safe demo that gets a good reaction out of just about any age group. You make a supersaturated solution of sodium acetate in a spotlessly clean beaker. Show everyone the clear liquid (looks like water) then start slowly pouring it on the table. Crystals of sodium acetate form as you pour, and the water is trapped within the crystals. You wind up with a pile of fairly dry looking sodium acetate and no liquid. Very impressive. Sodium Acetate Tower
Another one I like is the burning carbon disulfide demo. I've seen this done using a long glass tube full of carbon disulfide gas. Drop a glowing splint in one end of the tube, and as it falls you get an amazing blue flame. Here's a link (hope you speak a little German) CS2
They did it a bit differently. As you might guess, this lab is a bit more hazardous and you do get some stink from the sulfur. It's pretty though.
Making your own mirror is another great demo. You prepare a small batch of silvering solution. ISTR using silver nitrate and nitric acid, maybe using an aldehyde as a reducing agent. I'll try to link to a recipe. Anyway, you mix the solution in a round bottom flask and begin swiriling. It takes about a minute, but as you swirl a silver mirror plates out onto the glass. Tollens Mirror
I used a bit of a different procedure, but this looks like it should work. You may consider keeping the flasks a little on the warm side (100-120 F) just before you do the demo. I've gotten better results compared to using cold glassware.
A great set of books is Tested Chemical Demonstrations, Vol. 1-4, by B. Shakishiri (University of Wisconsin Press.)
This explains how some guy I saw on that Ripley's TV show poured molten lead into his mouth without burning the crap out of himself. It's been a while since I watched it but IIRC, he seemed to keep it in a pool on his tongue for a couple of seconds and then spit it out.
It's long been a running joke that people with Physics degrees end up in the Unemployment line. But now when you go to the fair and see a circus geek sticking his hand in molten lead, ask if he went to M.I.T. And the guy next to him that bites the heads off of chickens may have a PhD in Philosophy.
- Make Nitrogen triiodide crystals and detonate them (the purple crystals explode when jarred)
- Electric pickle - make a pickle glow!
- Oobleck! Corn starch and water combine to make a substance you've got to handle to believe.
These are just a few, the sites I pointed at above have other similar projects. Have fun!"It is our blasphemy which has made us great, and will sustain us, and which the gods secretly admire in us." - Zelazny
A piece of plywood, a sheet of plastic (shower curtain), and the absolute cheapest electric leafblower you can find will slide a 200lb person all the way across the gym floor.
1 cup cornstarch
1 cup baking soda
3/4 cup water
N drops of food coloring
At least that's the way I have done it.
When men used to be men
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 :)
You mean like this?
grnbrg
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
Here's a colorful one:
:).
Try putting (about) equal volumes of CCl4 (carbon tetrachloride) and aqueous KI (potassium iodide) in a test tube together. The clear, non-polar CCl4 will sink to the bottom, and the clear, polar, KI solution will sit on top. Now add a few drops of Br2 (liquid elemental bromine) to the solution and shake. The top layer will turn orange and the bottom will turn pinkish purple, but stay totally separate.
This reaction happens because bromine is a stronger oxidizing agent than iodine. When the bromine is added, it replaces the iodine in solution, forcing it to become I2 (elemental iodine) which mixes with the CCl4 below and turns it pinkish purple. The extra leftover bromine turns the solution on top orange.
It may not be as exciting as blowing something up, but it illustrates an important scientific principle (relative strengths of oxidizing agents) and it still looks cool
That is if you like having an anvil on your chest...I've seen this done, but I'm not sure if you have to hold your breath or keep your chest expanded(likely). Very neat though, as it seems certain to the viewer that the person under the anvil must be crushed by the hammer blow.
What's in a Sig?
Keep in mind that each collision has to be such that the weight of the first object (i.e. tennis ball) is negligable compared to the second (basketball). Perhaps you'd be able to get it down to orbital velocity, but the size of the balls would be going down as well. I doubt that the last ball would be big enough to see with the naked eye, unless the first ball you started with was very, very, large.
Also, I am fairly certian that IF you couldn't get up to orbital velocity because you'd reach terminal velocity first (i.e. drag would be such a problem that there's no way anything would leave orbit).
Several hundred feet is probably a better target to shoot for with such an experiment (though that may fail, too).
There's a reason that the highest flying toys are rockets. They can get the highest the most.
Mod me down and I will become more powerful than you can possibly imagine!
These are all great. Here's one I havn't seen yet:
Boil a few ounces of water in a tin can so the can is full of steam. Then with tongs, invert the can into a bath of cold water. The can crushes itself instantly.
--Ben
might as well get 'em started early. Make beer. If you need a demo, watching active fermentation is more exciting than a lava lamp!
The demonstration at the equator, as shown on BBC, that demonstrates how the direction of rotation of water going down a drain reverses on account of moving a couple of hundred feet across the line was also amazing. But it was not genuine. It's bunko artists who are quite skilled. Lots of experiments like that one.
A torsion pendulum that can demonstrate the gravitational force from movable masses would also be a great demo.
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?
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
This is actually a lot more fun if you put your hand on fire. It is possible and quite safe. Add some salt to the mix to, to get a yellow flame rather than a blue one.
Employee of Inrupt, Project Release Manager and Community Manager for Solid
I'd say: get a bed of nails. The bed of nails is probably the demo that hurts the most of the things I do, but it is not dangerous. It doesn't hurt just lying there, but then you put some brick s on you chest, and you get someone in the audience to break them with a sledgehammer. But it looks absolutely astonishing.
Check out David Willey's homepage. There's not much info on how to do things, but he does all kinds of weird things, and he's the guy who organized these firewalking record events.
Employee of Inrupt, Project Release Manager and Community Manager for Solid
Fill paper cup with water, place on bunsen burner. Because the paper is thin, the cup is a fairly good thermal conductor. The paper never get's hot enough to catch fire as all the heat from the burner is conducted into the water.
I don't know about the Leidenfrost effect, but drinking liquid nitrogen is absolutely not safe. There was a notice in New Scientist not long ago when some undergraduate tried this, and failed. He spent like 3 weeks in intensive care, and parts of his stomach had to be replaced, IIRC.
So yeah, it looks cool (yes I've seen it), but personally I'd rather be slightly less cool in the eyes of the audience and not risk spending a month in intensive care. Of course, YMMW.
Demonstration of the Ideal Gas Law:
;)
:)
;) http://caselaw.lp.findlaw.com/cacodes/pen/12301-12 316.html
PV = nRT
Pressure × Volume = No. of moles × Universal Gas Constant × Absolute Temperature
First off, you will want to do this outside. All you need is a small amount of dry ice, water, and a plastic soda bottle (20oz, 1liter, or 2 liter are all fine). I would reccomend a 2 liter, because it's more impressive. Put enough dry ice in the bottle to barely cover the bottom of the empty 2 liter bottle. Then be ready for action, because you will want to put about an equal amount of water as dry ice in your bottle. After filling the bottle with water, the dry ice will start being convered to CO2 gas, and you will want to cap the bottle. Place it in the middle of a field or something and make sure everyone is well away from it.
You can take this time to explain that Dry Ice is a solid form of Carbon Dioxide, and when it is in a system with water, it undergoes sublimation (solid to gas, no liquid phase). And that it's gaseous volume is 800 times that of the solid volume. (so if you want to measure and get all scientific, you could).
Just about when you get done explaining this stuff, your experiment should alert you that it's ready. The pressure that the CO2 exerts on the closed volume system becomes too great, and the bottle gives and a rather loud sound is produced. Like everyone said, explosions are cool
So if we apply the science to it.
2 liters = (approx) 2000 cubic centimeters
2000cc/800 = 2.5cc of dry ice needed to fill the system with gas.
So lets say we put 5cc of ice, and 5 cc of water in.
5cc * 800 = 4000cc space needed for the gas to expand
system volume(2000cc) - water volume(5cc) = 1995cc
This would pretty much gaurantee an explosion. But for the kids, you might give them this information and see if they can come up with the minimum amount needed to make the bottle explode, make them draw upon some basic math skills
Ok, now that I've gone though all this, check your state laws to see if this fun experiment is illegal, it is here in california
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.
Employee of Inrupt, Project Release Manager and Community Manager for Solid
When I was studying chemistry I had fun with this. Sorry, I'm used to MKS system. Prepare 1 liter of solution containing: 10 grams of NaOH 10 grams of C6H12O6 (any of the 16 works, only changes speed) 1 drop of 1% solution of Methilene-Blue (well, I've never used a drop, but directly joined a couple of grains) Fill half a bottle and close it. Within a little time it seems clear water, since NaOH+C6H12O6 turns Methilene-Blue to a not-oxidized state, but as you shake the bottle, the Oxigen takes it to blue again, then it turns again clear... You can repeat it some times; open the bottle if it doesn't work anymore: maybe you've consumed all the Oxigen... Have fun!
One of the most exciting on-the-benchtop physics experiments I have seen was a Wilson Cloud Chamber detecting cosmic rays. So simple yet it makes radiation visible. I was spellbound by something this simple.
Iodine clock reactions are the bomb. Especially if you pour your mixture back and forth between beakers so a stream of it is cascading at the time the color changes.
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).
In high school, I was often asked to visit the lower school to do science demonstrations.
The all-time favorite was the Van DeGraff generator. There is something about your hair standing straight out that always amuses the kids. I also lit fluorescent tubes in my hand.
I got the best results by making them stand on a milk crate to keep them from discharging through the floor. Before they got down, I had them "slap me five" so they didn't feel the spark discharge.
You can use the demonstration as a lead-in for static attraction and repulsion and a whole raft of other topics depending on the age group.
Just make sure you get a -small- one. The one I used was 18 inches tall and came from Edmund Scientific.
By the way, if you haven't been to the Boston Museum of Science, then you haven't seen the worlds largest Van DeGraff generator. Quite a show!
http://www.mos.org/sln/toe/
-jake
sheesh. We got some crazy people here. Seems like everyone's messing around with liquid nitrogen and microwaves and such.
The stuff I remember is a lot simpler:
bending water stream
1. air up a baloon and rub it against some cloth to get a nice clump of static electricity.
2. go turn on the tap water and hold the balloon really close to the stream *without* touching it. You will see the water bend towards the balloon. Fwee.
crushing can
you need tongs, a heat source (like a stove), a pot of cold/room temperature water, and an empty metal pop can
1. using the tongs, hold the pop can right-side up over the heat source until the can is really hot.
2. now quickly, still using the tongs, place the can upside-down into the water (part of the point is to make sure the mouth of the can is completely covered.)
The can should now be quickly and dramatically crushed. The reason is difference in air pressure coupled with rapid temperature change.
Also, of course, the levitating magnet thing is cool (superconductivity).
Another source for science demos is magic books. Go to some bookstore and pick out an interesting magic book. Just skim until you find one that exploits more science or math than misdirection. Some do, some don't. It's also possible to use magic tricks to get kids' attention and make a dramatic impression, as this post by DaveNay (532546) humorously demonstrates.
Furry cows moo and decompress.
Please clarify "plasma balls" and "between legs".
I used to be the lab tech in a lead smelter. One day, taking the temperature (about 680F) on a kettle of soft lead (non-alloyed), a refinery rat ran a forklift into the stack of pallets I was standing on, causing me to fall partway into the kettle. Fortunately, Most of my body was below the level of the rim, so I kind of landed on my upper ribcage. My left arm, holding the thermocouple, went in up to the elbow... for about 200 milliseconds.... It's amazing what terror can do for you. It was, as always, about 130 degrees in the refinery, plus, I'd been helping skim a kettle, so I was pretty sweaty. I ended up with a somewhat pink arm with silvery, lead-covered hairs, and a melted thermocouple handle. The refinery supervisor joked that he was afraid they'd have to do a "de-shit" treatment on that batch.
It didn't even merit an incident report. The whole place was a death trap. It was pretty common to have one guy point out to another that he was on fire, and have the burning man ask to be put out, because he had his hands full. Quite a place.
My chemistry teacher last semester pulled this one:
He had a couple of gasses in class, one of which was helium, and the other was a heavier-than-air gas, bromide something, I believe. To show us both how vibration worked, and something about gas laws, he sucked down first some helium, which we've all done, and know that it makes your voice very high. Then he sucked down some heavier-than-air gas, and his voice became very low. Then he had a girl in the class do the same thing.
Interesting.
sig?
Check out this group's (Lifters) web page for amazing experiments in what appears to be anti-gravity. There are simple and complex plans for others that wish to re-create these experiments.
http://jnaudin.free.fr/html/lifters.htm
There's even a cool Escher print based on it.
The two "neat" experiments I remember professors doing in a chemistry lecture were:
1. lighting balloons of hydrogen. I think this was most impressive because people are conditioned to think that floating balloons on strings are simply helium. I came a lecture hall on my first day of freshman chemistry there were several balloons on strings... how cute. Then the professor lights a dowel rod about a meter long and pops each of the balloons. The resulting explosion is quite bright and loud. Good attention getter.
2. inhaling argon. I'm not sure how safe this one was, but as most people know you can suck in helium and get the whole Donald Duck voice thing. I also had a professor inhale argon (significantly heavier than air.) The resulting voice is very deep and eerie sounding.
Get a box, about the size of a bread box actually. Cut a 2-4 inch ROUND hole in one side, and cut most of another side off the box and replace with a plastic sheet, like a garbage bag or a length of saran-wrap. You need to be able to open and close the lid of the box still.
Now the danger (it isn't science if it isn't dangerous), light a piece of paper on fire, on a plate or something fireproof, and blow it out pretty quick so it generates a lot of smoke. Put this in the box and seal it up (make sure the flame is out, but still makes some smoke)
Now tap on the plastic side of the box and you can blow BIG smoke rings out the hole. You can shoot these things like 20 feet.
And now the kewl part, set a candle up about 10 ft from the box, and blow it out with the smoke ring. If you hit the candle with the center of the smoke ring, you blow it out. If you set it up on a table and get the aim down, you still blow the candle out after the smoke runs out.
BTW: This will set off smoke alarms and the like, so be prepared for that. If you disable your smoke detector, why not put a new battery in it while your there?
M@
Krispy Cream is people
I wish I could remember what the solution consisted of, but it is a neat little experiment that teaches that various phases of matter (in this case solids and liquids) can have the same index of refraction despite being very different chemically and physically. Hope ya like it!
today is spelling optional day.
For this simple demonstration of vacuum you need an orange, a vessel (a drinking glass or cup with a diameter smaller than the orange), a small piece of combustible paper, and a match or lighter, to ignite the small piece of paper.
Put the paper in the vessel. Ignite the piece of paper. While the flame is going strong, push the orange firmly against the opening of the vessel. The flame will starve off to nothing pretty fast. More importantly, the gasses inside the vessel will cool rapidly, creating a vacuum inside the vessel.
You will then find that the orange is stuck quite stubbornly against the mouth of the vessel.
Kids usually like this.
By including this sig, the copyright holders of this work or collection unreservedly place it in the public domain.
When I was a cubscout leader, I stumbled on a cool idea used in a ceremony. Soak a cloth in a mixture of 40% acetone and 60% water (keeping it in a sealed jar so the acetone doesn't evaporate). Then you can light it on fire, and the evaporating acetone burns, but the cloth itself doesn't. A link to the details in the context of cubscouts is here
I've seen it demonstrated by Jack Cohen (science writer and reproductive biologist). Its cool.
Do a google search to find a number of recipies.
Paul.
You are lost in a twisty maze of little standards, all different.
The average laymen thinks scientists are just playing with toys when they see museum demos or visit a "science" store. They forget that science is a way of thought based on reproduceable experimentationa nd observation. It has generated more wealth per average living human being in the past three centuries than the tens of thousands of years of human existance under alternative ideologies.
I actually did this on Friday night for the first time. If you coat it in saliva and roll it around your mouth, the nitrogen will never actually touch the inside of your mouth.
To be honest, I have forgotten the details of most of these experiments, so while I cannot give you exact methods or reasonings, the gist of the experiments should come through enough for you to consult with other sources and collegues to fill in the gaps of my mind.
To that end, the experiments:
1) Measuring the speed of sound - from this one I remember we first determined in class how you could measure the speed of sound, variables, and how you would set up the experiment, then what the answer would work out to be if done a certain way. Then, the class was led outside, and one person held two sticks and banged them together. Another person was instructed to listen for the return sound from the science building we were standing away from some number of feet. Someone else was timing with a stopwatch. I am not sure of the process, but from all of this we got data that we used in class to determine the speed of sound, based on how we should do it - we weren't that far off, if I remember right, for our height above sea level and the condition of the weather outside - and we were real close to what we had gotten in the classroom.
2) Hitting a target - perhaps a little closer to home today than then - basically calculating trajectories, parabolas, etc. In the classroom, we calculated given a certain amount of pressure in a rocket (we used an air powered rocket for safety and distance reasons), angle, etc - what was needed to be put into the rocket in order for it to hit a target set some distance away. Once we had calculated that, we then went out on the football field (to the amusement of the PE class of the period), and launched the rocket. We hit the target, as our calculations said we would (now, class, can anyone tell me how an ICBM works?).
3) Measuring the mass of an electron - OK, this one is REALLY fuzzy in my mind, and in the end, we were off by a whole heck of a lot, but not as much as you would think given the equipment. All I really remember about this was some very complex mathematics, a bit of reasoning, and the use of an old occiliscope and power supply.
4) Water below freezing - in this experiment, which involved more than I am letting on here - we showed in individual labs how you could keep water liquid, even though you brought it down below freezing. We used stainless steel containers, regular water, ice and salt in a styrofoam container to bring the water down that was in the stainless steel container, some thermometers, etc. I also remember another part of the lab that involved a different substance, that you heated, it went from solid to liquid, then you gradually cooled down to room temperature (by lowering the bunsen burner flame), but it stayed liquid. Then you let it cool off really well, still liquid, then you put in a seed of the solid substance, and it immediately crystalized solid again (in time for the next class, I suppose). Cool thing to watch.
Those are the ones among my favorites. They could be enhanced in different ways (like the trajectory one - build a spud cannon instead for the demo, on a stand that permits tilting it like a mortar, at known angles). Hope these help - good luck!
Reason is the Path to God - Anon
This is an experiment I did in a chem class back in high school. My memory might be a bit fuzzy.
:)
Pennies are not all copper, but a thin copper 'shell' around another metal. With a small file, file a few (3 or so) notches in the sides of the penny so that the other metal is exposed. Place the filed penny in a beaker and cover with acid (I don't remember which acid, probably sulfuric). After a while the acid will have 'eaten' away the other metal, leaving only the copper shell. This shell (you did wash away all the acid, of course) looks indistinguishable from an ordinary penny. Watch the students' faces as you throw the penny into a glass of water and it floats - then pick it off the surface of the water and crunch it into a little ball with your mighty fingers
Caveat Emptor is not a business model.
I know it's aluminum foil. That's just the common term.
If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
According to: Bartholomew and the Oobleck make Oobleck
The recipe will make enough for a class of 30.
YOU NEED: ~a large mixing bowl ~mixing spoon ~green food coloring ~10 cups (21/2L) of cornstarch ~6 cups (11/2L) of room temperature water
DIRECTIONS: Put water in the large bowl and add food coloring drop by drop until the water turns green. Now mix in the cornstarch a cup at a time. Mix throroughly. Have some extra cornstarch available for thickening the mixture. Place a glob of the mixture in a paper cup and give one to each students.
jred
I'm not a mechanic but I play one in my garage...
Lindsay books is a good place to look for books on this line. (Get the catalog, it has more than the website lists) Several books contain interesting science experiments that you can try. Along with many other fun projects that Geeks will love.
Not sure, but I think I had the same reaction when I dropped a couple of Mike 'n Ike's into a can of Coke.
:/
Only happened once, though.
What's this Submit thingy do?
My high-school AP Physics book had an article in it written by the author. There were a couple of demos he did frequently.
First was dipping his hand (wet!!!) into molten lead. He stopped that one when the lead got caught under his fingernails.
Second was putting liquid N2 in his mouth. He could blow clouds of fog for five or six feet. He stopped that one when the N2 contacted (and contracted) his front teeth. (His dentist convinced him to drop that one.)
Third was firewalking. He reasoned that his sweat would protect him from the coals...It worked until he was too comfortable with the idea to produce enough sweat.
He did find a demo that worked. One easy way to demonstrate the Liedenfrost effect was to heat up a frying pan to well, well beyond water's boiling temperature. If it's hot enough, individual drops of water will float on a tiny bed of steam, and dance around the pan for several minutes.
(I'd be careful about that one at home...Fires have been started from the pan's heat radiation. Don't leave it unattended. Keep a fire extinguisher handy.)
What's this Submit thingy do?
Here are three experiments that I've seen/done that I've thought were very impressive.
1. Take an empty gallon paint can. Drill a 3/8" hole in the center of the lid, and in the side about 1/2" from the bottom. With the lid on, purge the inside with natural gas. Now set it on the floor and light the top hole. This will produce a steady flame 2 or 3" in height. Now you have to do some acting. Make it seem like something cool is going to happen and get the viewers to watch intently. After a minute or two they will start to get bored as all that will happen is the flame will slowly appear to die. After a certain point, tell the viewers that something went wrong with the expermient and you'll have to try again once the flame has died out. As time progresses, the flame will grow smaller and will actually disappear from sight as it drops below the hole. Fairly shortly after it does this, the ratio of oxygen to gas in the paint can will reach the appropriate mixture and will explode launching the lid of the paint can about 8 ft' straight up, and startling everyone who has forgotten abot it. Obviously, this needs to be done well away from the audience.
2. This requires two large bricks of dry ice (about 12" square, 4-5" thick), some magnesium shavings and a blowtorch. Take the bricks of dry ice, and hollow out a small area so that you can stack them trapping a small pocket. Put the magnesium shavings in the pocket, and light them with the torch. Put the other brick on top sealing the thing in. Because magnesium can use carbon dioxide as it's oxygen source, it will continue to burn inside the dry ice. It produces a really incredible glowing effect from the ice. After burning for a while, the glow will reduce and will actually begin to pulse.
3. Finally there's Peryoxyacetone (sp?). I don't remember exactly how to make it, but you can find it in Chemical Demonstrations: A Handbook for Teachers in Chemistry by B. Z. Shakashiri. The books are excellent as a whole, the the peryoxyacetone, is escpecially impressive. It's a white powder that burns in a nice big fireball. It burns quickly enough (and at a fairly low temperature) though that it can be used to demonstrate the leidenfrost effect. Placing a small pile on the open palm of your hand you can light it, which creates an impressive looking fireball that you can't even feel. I'd suggest trying this on a piece of paper the first time. If you've got the right stuff, there won't even be a scorch mark on the paper.
I used to teach an activity class at Camp Susque called "The Wonder of it All" which was basically neat science expirements with the explanations. To begin every week, all the counselors would do a short skit to excite the campers about the activities. I did a skit called "red eye." I'm not sure who had the idea originally, I sure didn't make it up, but the skit was always incredible and wowed the kids.
Here's the synopsis of the skit, I'll explain how it works afterwords:
Sitting at a table is a bartender...washing his glasses. A rough looking character walks in and demands a glass of redeye (pink lemonade works better and is more funny). The bartender grabs a pitcher full of clear liquid and pours it into an empty glass. The glass fills up with a red/pinkish liquid. Another guy walks in, a city slicker, and asks for some water. The bartender, pouring from the same pitcher, pours a glass of "water" into an empty glass. The rough looking guy laughs at the city slicker and tells him he should try the lemonade, and that he'd pay for a new round. The bartender grabs both glasses, pours them into the pitcher (the liquid turns pink), and the bartender pours out two glasses of the pink liquid. At this point, a sheriff walks in and asks for some water. The bartender pours the pink liquid into an empty glass and the liquid instantly turns clear as it is poured in. (A lot of wows from the audience at this time). Here's the big finally: The sheriff says that lemonade is bad for you and that the two guys should try some water. The guys (strangely) agree and give their glasses of pink liquid to the bartender. The sheriff also hands his glass to the bartender and says he'll pay for the round of waters. The bartender pours the sheriff's "water" back in the pitcher which instantly turns into a clear liquid. After that, the bartender (slowly because it looks so cool) pours the pink liquids into the container (so you see a pink liquid pouring in and it becomes clear the instant it touches the water...looks very cool). The bartender then pours out a round of "water" to the three customers. *curtain* *Applause*
The effect of this trick is pretty dramatic (without blowing anything up!), and it is QUITE simple with no special chemicals needed. The only things you need are ExLax, rubbing alcohol, and white vinegar, ammonia and water. To prepare, I would take and exlax pill and grind it up and mix it in a quarter cup of alcohol. This would provide enough solution for 10-20 skits. The mixture you just created is poor-man's phenolphthalein, a chemical that detects acid and turns red when it finds it.
Prep: Get three clear glasses and a pitcher. Take the phenolphthalein and put a few drops (10-15) in the bottom of a clear glass (the ruffian's glass). Put about twice that much ammonia in the bottom of the sheriff's glass. Leave the cityslicker's glass empty and unchanged. In the pitcher, add a few drops of white vinegar to about a quart of water.
How it works: when you pour the vinegar water into the ruffians glass, the phenolphthalein makes it turn a bright pink/red. When you pour it back into the pitcher (before pouring the lemonade for both the cityslicker and the ruffian), it will turn the entire pitcher to a bright pink. When you pour the vinegar/phenolphthalein water into the sheriff's glass, the ammonia (a basic substance) neutralizes the acid and the phenolphthalein will no longer be red...so the sheriff will have clear water. When you pour the sheriff's "water" back into the pitcher, any remaining pink water turns clear and as you pour the other two glasses of pink water in, they will be neutralized. Leaving you with a clear neutralized liquid.
Again, the skit works great and it is a lot of fun...however, a few things to remember: practise it a couple of times to get the amounts down right (I always estimated with the amounts, so I'm not sure if my drops and measurements are right), and DON'T DRINK THE LIQUIDS! Ammonia is not good for you and vinegar is nasty. One more thing..I know ex-lax was taken off the market for a while because it was supposedly carcinegenic. I think the chemical that was problematic was phenolphthalein....so, I don't know if exlax can make poor-man's phenolphthalein anymore. Try it out (even w/o phenolphthalein, the replacement might do the trick), and if it doesn't work, just buy some regular phenolphthalein from a pharmacy or chemical supply house (it isn't uncommon...I remember using it in 7th grade chemistry).
Another couple of cool hand's on expirements we did in the class were simple bakingsoda/vinegar expirements using film canisters (make sure they are the lids that pop into the container, not that ones that have the lid that goes on the outside)...add a bit of vinegar in the container, put some baking soda in the lid, pop the lid on, shake it, throw it...BOOM!
Other expirements included balloon rockets, water rockets (with an air pump and 2 liter soda bottles...you could get the suckers to shoot REALLY high!), polymers (magician's slush powder makes it even better) that soak up 100 times their weight in water, cornstarch and water (makes a pseudo solid...hard under pressure but liquid when released), making huge epson salt crystals on pipe cleaners, etc...etc. I'll think of some more, but if any of those expirements sound like fun and you need more info on them, shoot me an email [peter@peterswift.nospam.org] and I can give you detailed instructions on each one.
Still anything with explosions, dry ice, liquid nitrogen etc still seem to be crowd favorites.
Another crowd pleased is covering your arm with rubbing alcohol and igniting it and running around screaming then say it didn't hurt at all (make SURE YOU SHAVE YOUR ARM FIRST! ARM HAIR BURNS AND HURTS A LOT...not speaking from experience or anything *cough*).
The anti-salmon
In eighth grade, my science class was using a program called "ISCS" which stands for some sort of "independant study curriculum science" or something like that. Basically, we were split up into lab partners, given books and set to work. There was no limit to the amount of chapters you could get done, and my lab partner and I were very competitive and we wanted to be the first people to complete the book in the year. Towards the end of the book we were on chapters that required chemicals that our teacher hadn't mixed for us yet, so he generally let us use the chemicals straight from the stock jars in high concentration...he would just have us use much less of them or he would have us mix our own stock solutions. Generally, all the chemicals got thrown down the sink (a science lab sink that had containment below the floor for the organic stuff or something) with liberal amounts of water. However, when we reached chapter 23 we had to do an expirement that required sulfuric acid, sodium thiosulfate and "winkler's" solutions 1 and 2. The teacher gave us the straight solution without diluting it...telling us to be VERY careful because it was both expensive and dangerous (he didn't want to bother making a diluted solution because no one else was expected to reach that chapter and it would be wasted). So, we completed the expirement and proceeded to the sink where we planned on pouring out our extra chemicals. When I tipped the beaker of sulfuric acid...something interesting happened...all of a sudden there was a loud hissing sound and a HUGE cloud of purple gas throughout the room. I heard the teacher yell and the class headed toward the exit immediately. In the end, the class had to be evacuated (indeed, the whole science area) and the teacher (kindly) explained to me the dangers of pouring sulfuric acid down the sink and showed me the proper place for it.
Suffice to say, my lab partner and I were the first people to ever finish the entire book in one year and we finished it with over 5 weeks to spare. So, in the time that we expected to have fun and fool around, the teacher had us mix stock solutions of sodium hydroxide instead...which, if you couldn't guess, is incredibly boring.
The anti-salmon