World's Lightest Sold!

I've written about aerogel before (and perpetually mention the demise of my one piece).

But I haven't shown a video that uses a FLIR camera (1:00) to show the heat zones as they insulate a chocolate bunny from a bunsen burner using aerogel, where they show the industrial process of making aerogel (5:25), or especially where you actually get to see a supercritical fluid through the window (6:25 - the absolute highlight for a teacher who used to teach phase diagrams in AP chemistry), or where you get to see a mid-process 'wet' aerogel filled with alcohol (4:50).

If you happen to follow both of my blogs, you might see this double posted because of that supercritical fluid bit.

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The above the line stuff is what I wrote over on my material science blog because those folks care more about material science. Here, though, we care more about the chemistry, so I'm going to focus on the idea of a supercritical fluid.

The basic definition of a supercritical fluid is, from Wikipedia, "any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist. It can effuse through solids like a gas, and dissolve materials like a liquid."

See, the phase of a material depends on its pressure and temperature. We all know that water can exist as a liquid (between 0^oC and 100^oC at normal atmospheric pressure). Most folks know water can exist at even higher temperatures if it's under pressure (like in a pressure cooker). Below 0^oC at normal atmospheric pressure, water turns into a solid, but if pressure is applied (like underneath the blade of a sharp ice skate) that solid turns into liquid without warming above 0^oC.

If we graph all that, we get...

Source - http://wps.prenhall.com/wps/media/objects/4678/4791085/ch10_11.htm

In reality, water has a bunch of different solid crystal structures, so we could complicate things like this...

Source - http://ergodic.ugr.es/termo/lecciones/water1.html

...where each Roman numeral corresponds to one of the different, atypical crystal structures for ice. There isn't any real ice-nine, thankfully.

For carbon dioxide, as we see in the video up top, the phase diagram looks like this...

Source - same Wikipedia article for supercritical liquid as above

See that grey-blue area there, where it's not grey, and it's not blue but is rather a blend of them?

That's what we're seeing in the video.

And I've never seen it before.