I'm talking about the first half of the above video, during which Chris Rowlatt shows us how he produces marbled papers for eventual book binding. The marbling involves putting a nonpolar ink (or maybe dye, I'm not sure the technical distinction there) onto polar water. The two materials don't mix, so the nonpolar ink can be lifted from the surface of the water with paper.
I can't remember where I first saw this density bottle. It might've been from Educational Innovations at one of our ASM summer camps...or maybe from Flinn Scientific at one of their NSTA workshops.
Either way, I have one of those bottles in my classroom, and nearly every student who plays with it love and is fascinated by it.
There's so much goin on with the bottle (the full video of which you can watchin real time at 4:30).
There's solubility concepts - salt water and isopropyl alcohol being immiscible.
There's polarity concepts - food coloring being differently attracted to the two liquids (I recommend green food coloring not the red that Mould uses here. Just add green food coloring and see what happens.)
There's density concepts - the five substances in the bottle (air, isopropyl alcohol, salt water, white/translucent beads, blue beads) line themselves up by density.
There's polymer concepts - the two beads are made of different polymers (the company wouldn't tell me what polymers, and I've asked). The blue beads are sold as pony beads. The top beads - at least the ones in my bottle from Ed Inn - are sold as UV-detecting beads.
There's electromagnetic wave concepts - turns out that the less dense beads are UV beads. I'd had the bottle for years without knowing that because my classroom at the time had no windows, so I hadn't noticed that. Now that I know it, though, it's pretty cool.
There's IMF concepts - the bottle is shrinking a bit as liquid evaporates even through the bottle over the course of years. That's stunning to me, but I swear that I haven't opened the bottle even once in those years. Something must be going on.
But, see the mantis (murder) shrimp moves its...um...pedipalps, I think...so fast that they create cavitation bubbles which end up stunning its prey before the killing strike.
Didn't you watch PhysicaGirl's previous video about all that?
You should check it out.
I love that much of the video here is about fact checking a viral video - because the science we get from many of those videos is a whole bunch of bunk.
The science in this video mostly isn't about the bottle at all but rather about cavitation, a fascinating phenomenon that has all sorts of ramifications - like with corrosion, for example, or biology.
I love the slow-mo video of the bottle smacks - even down to the shockwave and soniluminescence.
Yeah, I guess hand sanitizer - mostly ethanol - fires are pretty hard to see, but I'm really glad that Steve Mould here goes into the dangers of methanol for the second part of his video.
If I haven't mentioned methanol to you yet, you should check out all of my methanol videos.
The fact that if you deform crystals, you can produce a voltage difference to get a spark...or that you can introduce a voltage difference to deform a crystal (like how a fan is a generator but in reverse or how LEDs are solar cells but in reverse) is amazing to me.
And Steve Mould's explanation of why that works - with the crunchy and smooth peanut butter lids - is just brilliant.
I'd known that piezo crystals were the guts of a grill lighter for a long time, but it was a long time before I found out other uses like the 'speakers' within greeting cards or microphones and guitar pickups.
There's an AP chemistry problem that I vaguely remember. The problem showed four balloons, each with initially identical volumes, temperatures, and pressures. The balloons were filled with helium, oxygen, nitrogen, and xenon gases respectively. (This is entirely from memory, but the details aren't 100% relevant to where I'm going with this.)
The questions underneath the prompt and diagram then asked something about which...
particles had the greatest average kinetic energy (they're the same because temp is proportional to average kinetic energy)
particles had the fastest moving particles (helium because Graham's Law of Effusion says that the smallest particles - if all are at identical temperatures - move the fastest to make up for the lower mass)
balloon had the greatest mass (xenon because they're at the same temp, pressure, and volume, so they have the same number of moles and xenon has the greatest molar mass)
balloon would be expected to be the smallest after a day
It's that last one that's relevant to this video.
In the answer I remember, the helium balloon would be the smallest because its particles are the least massive, so they're moving the fastest at the same temperature. That means they'll randomly hit the microscopic holes in the balloon (all latex balloons have tiny holes we can't see with our naked eyes - imagine a rubber band ball inflated), so the helium would get out of the balloon the fastest (it would effuse through the tiny holes) leaving the helium balloon the smallest after some amount of time.
But it seems like xenon might be the correct answer for a much more complicated intermolecular force reason.
I'm tempted to blog pretty much everything that he posts because the reactions are brilliant and often are things that I wouldn't remotely feel confident in doing myself. He's a chemist, and I'm clearly a chemistry teacher - very different training and levels of confidence with chemicals.
Recently, on his alternate channel NileBlue, Nigel posted a great video about the safety precautions that he takes in all of his work. The above video is long - twenty-four minutes long - but covers a great breadth of safety concerns from what clothing to wear to how to minimize risks by never working alone.
If ever you're tempted to do any chemistry at home - Nolan, I'm looking at you - you should watch this entire video and buy yourself a lab coat and some high quality goggles.
