5 Strangest Materials

MattSparkes writes to tell us that NewScientist recently posted a quick look at five interesting materials with some very strange properties. There are liquids you can walk on, liquids that will escape containers by creeping up the sides, and magnetic liquids that can easily show you the shape of magnetic fields. The story also offers video links to display some of more amazing properties described.

Comments

Number 6 - Elastic fluids

[Anonymous Coward]

They left out elastic fluids, such as a mixture of high molecular weight polyethylene oxide in water. Once the fluid begins to pour out of its container, it will partially empty the container, even if righted. This is the open siphon effect. If while pouring out the fluid, you cut it with scissors, the fluid will snap back into the beaker like a rubber band. This can all be done at room temperature.

What makes this happen is the high molecular weight polyer. The molecules become entangled, and when poured, they pull each other along, resulting in the emptying of the container.

These fluids also exhibit other interesting behaviours, such as the Weissenberg effect, where when rotating rod is placed in the fluid, the fluid climbs up the rod. Also, add some particles (or bubbles), start stirring, then suddently remove the stirring rod, you will see the fluid snap back when it comes to rest.

Try this at home - if...

[jpellino]

... you have to mix the non-newtonian fluid pretty accurately - too thin and it won't support you, too thick and it's trivial... you'll notice they have a stirrer of some sort in the pool video - this is important - this stuff can settle in short time so you end up with mostly water above and mostly cornstarch below. Jearl Walker once lept over tables into a feed trough full of this stufff on his show. He didn't splash a drop. He did, however lose his balance, and tipped the whole thing which slowly flowed into the audience...

And they mention conrflour - I'd stick with cornstarch. One time going France and Hungary to teach science, I figured I'd forego the big containers of white powder on the international flights... and getting to Nice, I found that you can only buy boxes of cornflour, not boxes of cornstarch in French grocery stores. You could get sugar-packet sized envelopes of it, which were labeled in French with something I could not read but I imagine said "You are in France. We are famous of our sauces. If you need cornstarch to make a sauce, then go away!."