Have you seen... [crystallization]

Here are two cool illustrations of materials crystalizing - both the effect and the crystals' appearance are neat.

The first video uses a super-saturated solution of sodium acetate, and the demonstrator triggers the reaction with a single crystal.  In his second display, he pours the solution onto crystals, and the resulting growth occurs so quickly that it forms effectively a stable stalagmite on the plate!

You'll have to pardon the voiceover on the next video -- it sounds like he's in the witness protection program.
The experimenter uses a solution of silver, and crystallization requires some electrical current applied.
He repeats the process with a higher current (crystallization occurs much faster) and with a solution of silver nitrate.  When viewed through his microscope, the effects (some time-lapsed) are beautiful and fascinating.

Have you seen... [Newton's beads and Newtonian liquid]

There are more interesting phenomena with "newtonian" materials...

First, "Newton's beads" (and goopy liquid molecules) use gravity for all it's worth:

Second, a Newtonian liquid creates an unexpected effect when being poured into a different flowing liquid:

I would love to be one of those guys that does fun science demonstrations in schools, on TV, etc.!

Have you seen... [smoke rings & bubbles]

When air in a container is forced through a circular opening, the edge of the opening will create a vortex ring.
Wikipedia helps illustrate what a vortex "looks" like:

In the real-world, we can see this turbulent effect in smoke rings - the particles make the phenomenon visible.
But why let smokers have all the fun, when you can make or buy a vortex ring bazooka!  (Smoke not included.)

Here is Ellen having fun with an easy, homemade air vortex contraption on one of her shows:

In rare cases, a volcano will create a massive smoke ring sending it hundreds of feet into the sky:

A completely different playground activity usng air with another material is the creation of soap bubbles.

Soap film "stabilizes" the surface tension of water and makes sustained (short-term) structure possible.
Like oil on water, the colors we see are created by reflection and refraction of light on the surface.
The light's frequency (phase) is shifted differently, based on the thickness of the soap film on the bubble.

It's a favorite children's activity, but in the second video a "bubble artist" shows just how far this can go.
He creates "doughnut" (torus) shapes, bubbles with smoke in them, and bubbles within bubbles.
And he got a grant from the U.S. government to mess around with bubbles too - why didn't I think of that?

Have you seen... [laminar fluid flow]

The video below is not the most dramatic or exciting... until a subtle surprise at the end.

Here's how it starts:  drops of three colored fluids are placed in a small container of water.  A crank is turned at the top that forces the water to circulate.  After a 6 1/2 revolutions the colored drops of liquid are pretty well "mixed" and the person stops, then starts turning the crank slowly and steadily in the opposite direction...

Cool huh?  You might think this was just video done in reverse, to get the colored drops to re-form like that.
But it is the result of highly laminar flow -- very little turbulence (mixing) -- that keeps everything "in parallel" and the "mixing" therefore becomes a "reversible" action!  (Note that this demonstration is also enabled by the fact that the colored liquid drops have a higher viscosity than the surrounding water.)

One can take advantage of the steady, parallel properties of laminar flow in water fountains.
By ensuring laminar behaviour, water streams will hold their shape.  Even further, light can be projected onto or into the stream (where it reflects back & forth inside the stream) -- this creates neat visual effects.

It can be mesmerizing.

The water fountain in the next video adds two more tricks to the show.  First, the water is pulsed on & off to give a projectile-like effect,  Second, some water streams are aligned so that they collide in midair, and where they meet become a shower of (turbulent) droplets.  This was installed at a casino, no surprise there!

I 've enjoyed a similar fountain at the Detroit Airport during some travels.  Hope to see more around.

Have you seen... [non-Newtonian fluids]

It's great when nature throws us a curveball.  (E.g., most liquids contract when frozen, but water expands).

Most fluids are "Newtonian", meaning that they continue to behave basically the same way no matter how they are being manipulated (stirred, shaken, flowing in pipes, etc.).  It will always act like we expect it to.

A non-Newtonian fluid, however, can demonstrate unexpected viscosity in certain situations.
Everyday substances found in ketchup, custard, paint, and shampoo can result in non-Newtonian fluids.  In the first video, a simple starch solution on a loudspeaker cone shows how unusually the fluid behaves when disturbed.

Many liquid polymers are non-Newtonian, and also exhibit the Weissenberg effect.  Without going into detail, this effect is that the fluid is not thrown off a spinning rod, but drawn into and across the rod (in this case, going up)!

The Kaye effect is another fluid phenomenon.  In this case, when a viscous fluid like shampoo is poured onto another liquid, something about the surface tension and interaction create a second stream coming up.  Interesting...

Have you seen... [wave frequency and harmonics]

Some of the best science demos reveal something to the viewer -- making the previously unseen become visible.

In this case, a Ruben's tube is used to visualize how sound (mechanical waves) influences air pressure in a tube.  Standing waves are the easiest to visualize, but the musical dynamics and complexity are interesting too.
Plus it uses fire and rick & roll, which always makes such projects more exciting!

By the way, after the Dave Brubeck jazz, did you see the flame gap with the rock music?  I wonder if that has anything to do with how it is equalized when mastered...

Mechanical waves can create energy patterns in solids as well.  This is a clever use of salt on a vibrating table to show more complex harmonics.  The shape and composition of the table are also important here -- this table is "clean" enough to get distinct constructive and destructive effects that result in salt "mounds" and clear spaces:

Have you seen... [science and soap]

This is a classic science demo for classrooms.  Using soap, create bubbles from methane gas (e.g., in cigarette lighters).  The methane, less dense than air, makes the bubbles rise and they are flammable with cool effect:

(Note:  due to the difference between temperature and heat, plus the fact that methane is less dense than air and rises, the instructor/teacher can have the bubbles lit in her hand without being burned.)

Television has caught on and entertains with bubble sculpting and even larger flames...

Sublimating dry ice (solid carbon dioxide) to make soap bubbles produces an entirely different (but neat) result:

And for those that don't want to light your house in fire with methane, simple Ivory soap can be fun too: