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Probably my favorite kitchen experiment has always been to put water and pepper into a small bowl, and then dip a toothpick with dish soap into the middle, causing all the pepper to instantly and dramatically scatter away from the toothpick.
YMMV of course, but I always felt that it demonstrates something that's not all that visible and obvious otherwise - I feel like a lot of kid-friendly science experiments give an expected or intuitive result, whereas soap's weakening of intermolecular forces in such a dramatic and sudden fashion manages to connect the micro world with the macro world in a clearly visible, almost shocking way, while neatly demonstrating both why water is special and why soap is helpful.
I dunno, I just always loved it.
I always enjoyed the corn starch liquid or solid test where the mixture behaves like a liquid while being stirred but behaves like a solid when sitting still.
Non-Newtonian fluids are fun... until they aren't.
One time a group of college students I hung out with got a bulk order of silly putty. This was fun to play with. Until someone had the idea of dropping it from about 6 feet up onto the floor. It shattered. Picking up slivers of silly putty from the carpeted floor was not fun.
Elsefluid ... a different category (shear thinning - https://en.wikipedia.org/wiki/Shear_thinning ) has it so that if you drop something through it, it takes {some time}. If you immediately drop another thing through it at the same spot, it takes {some less time}. One of the chemistry professors wanted to do some experiments with this type of fluid and had his grad students develop a proof of concept. There are some challenges with this - it can't be a thin cylinder of the fluid you drop it through since the distance to the walls is a variable in the speed too. It also needed to be a tall enough cylinder with enough viscosity that you could time it with a stopwatch (initially). One such fluid that has this property is ketchup. They bought 10 gallons of ketchup from the local grocery store (that's all that was on the shelf ... seriously, you need about 7x 20 oz bottles to make one gallon), poured it into a large cylinder... realized that they needed a clear bottom to see it, made a new cylinder with a plexiglass bottom, and did the experiment. They dropped steel ballbearings from height into the the ketchup and timed the duration it took to drop one and the same spot that another had just traveled through vs a new spot. It worked and so they then worked on synthesizing 40 liters of a particular polymer that had that property (another significant effort - took much longer than buying 70 bottles of ketchup) but had the advantage that you could see through it.
> Picking up slivers of silly putty from the carpeted floor was not fun.
One of my science teachers in high school told me about the time she got a chunk of sodium and a 50 gallon barrel of water. She threw the sodium into the water. It blew up as expected. But it also fragmented into a million pieces, and those pieces hit the dewy morning grass and also exploded, triggering a chain reaction. I think she said the students had to run around and stomp out a bunch of little sodium fires. That demo was not done the next year.
> if you drop something through it, it takes {some time}
This is totally unrelated to your story, but it reminds me of the demonstration where you take a strong magnet and drop it through a copper tube. It takes forever to reach the bottom (because the moving magnet induces a current in the copper pipe, which produces a magnetic field in the opposite direction). Honestly, it's probably the one science demo that blew my mind when I saw it. It's SO slow. And we had already learned about the math behind it, but was amazing to see in practice.
> Honestly, it's probably the one science demo that blew my mind when I saw it. It's SO slow. And we had already learned about the math behind it, but was amazing to see in practice.
Many years ago (searching... Amazon 2017) got a fidget toy that did that... and digging around, its https://www.moondrop.space (It was $25 when I got it (for the set of three)... I wouldn't spend the current price on it).
From their website:
> Moondrop Lunar imitates the Gravity on the Moon.
> Moondrop Mars imitates the Gravity on Mars.
> Turn this Moondrop into Earth version simply by removing the magnets from inside.
I was wondering if they were just going to sell the last one without any magnets for the same price. Imagine the profit margin from people just wanting a complete set!
A truly amazing number of spelling errors per page.
Agreed it is a great demonstration, and I remember doing a similar one with an aluminum foil boat as a kid. Make a boat out of foil, put it in water, then add a few drops of dish soap behind the boat and watch it "sail."
The scientific name for this is the Marangoni effect [0].
The „Ölfleckversuch“ („oil stain experiment“) is very similar in setup but you use a drop of oil instead of detergent. Its volume and the covered area on the water surface are used to estimate molecular sizes:
https://de.m.wikipedia.org/wiki/%C3%96lfleckversuch
You might want to run this through your favorite translation service since there does not seem to be an English article on it.
My daughters have for years enjoyed dropping their plastic straws into their Jarritos bottle where it sits out of reach until the bubbles magically bring it back up.
This experiment always reminds me of Beakman's World because that's where I first learned of this. :-)
I wstched that show back in 2004 i think. For a year or so, i was hooked as a kid on.that show.
Never again watched it but that was a big science jump for me.
The thing is, i was a science kid from the start and discoverh and national geographic was amazing.
I remember watching a show "is.it real?" When i was like 7-10, not sure but one episode was about stigmata. Just random.thing i remember.
Then many years later, constantine movie i was watching on tv and i recognized the hand and said "thats stigmata".
Stuff like that happens with me daily. I like.it
It unearthed a memory of pee wee doing the raisins in club soda bit for me. (wow this show was nuts)
Comment was deleted :(
What a memory unlocker this comment is - loved that show as a kid
I must be a few years older than you... for me, it was Mr. Wizard's World that is stuck in my brain forever.
Don't miss this episode of Captain Disillusion with guest star.
Be still, my heart! I'm so glad PZ is still out there doing his thing
This reminds me of an old kitchen game also played with raisins, called Snap Dragon. What you do is scatter some raisins in a shallow dish then pour brandy over them and light it on fire. Then everybody tries to grab the burning raisins out of the fire and eat them. Fun for the whole family, but it fell out of popularity in the 20th century for some reason. I'm bringing it back though.
The article doesn't mention the Dancing Raisins TV commercial for California raisins — when I first saw it in 1986 I almost fell off the couch laughing. (But as Heinlein's Manny O'Kelly-Davis put it, it's a funny-once.)
God I remember my grandma just going nuts for the raisins. She had to find all the little collectible doll things.
What a weird trend.
I made a calcium fertilizer for my potted peppers last month, soaking dried eggshells in vinegar. They did a similar “dance,” though the bubbles were formed through the chemical reaction rather than a supersaturated liquid. I spent more time than I would have expected enjoying watching it.
Weightlessness no doubt ruins a lot of the fun we have on Earth, no doubt adds a good deal more though.
I saw the dancing raisins at Rutgers Brower's Commons dining hall either 1986 or 1987. The raisins from raisin bran in clear soda. People would do it as a table decoration.
I accidentally stumbled across this same experiment last week when my son put some sprinkles in his soda water. Cool to know it works with raisins too.
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