The mathematics of weight loss | Ruben Meerman | TEDxQUT (edited version)

Mrs Heckman and I were having a discussion one time about what happens to the fat - or whatever else - you burn when you lose weight. My contention at the time was that the fat was turned into carbon dioxide and water vapor which was eventually exhaled from your body - mostly as carbon dioxide but less as water vapor.

I don't, honestly, remember what her contention was...because it was wrong.

I do love the explanation of what the arrow (at about 5:00) actually means.

In the long run, it's just conservation of mass, and when we're talking about 'invisible' gases, it's an incredibly slippery concept for being so simple.

In all honesty, if my students could successfully answer the question he asked of the sunbathers on Bondi Beach, I'd be pretty happy about their conceptual understanding of chemistry.

There's a flip side to all this, and I'll post about that next week.

How Not to Put Out a Metal Fire - with Steve Mould

I remember watching WGN a couple of decades ago about a fire at a metals recycling company in Chicago (maybe this one?) The thing that fascinated me at the time was watching the firefighters spray water on the fire, have it explode, and repeat the process a couple more times. The fire chief at the time - in my deep memory, at least - said something to the effect that they knew the explosion was likely but that they were trying to dump enough water on all at once to cool the fire enough to stop the burn. Not enough water = explosion, though.

In the above video - the Royal Institute - Steve Mould shows why magnesium fires are such a bear to put out. They don't - as the article linked above says - 'produce their own oxygen', but they do tear oxygen off of carbon dioxide and water. Once that happens, then, the fire allows the hydrogen and oxygen (from water - or oxygen and carbon (from carbon dioxide) to react with the magnesium or with each other producing an even hotter flame.

Hmmm...seems magnesium's active or something.

(And I don't think - at 2:55 - you 'can actually see [the beaker filling with carbon dioxide]', Steve. My understanding is that carbon dioxide is invisible. What I think you're seeing is fog, condensing water vapor due to the coldness of the dry ice.)

Bagged Water in Space Has Weird Bubbling Behavior

I'll admit to being a sucker for just about any 'in space' video.

Here we see - and the space.com article explains - air bubbles not separating from the water surrounding them in a plastic bag 'in space'.

It looks impossible but makes absolute sense because it's not the IMFs that separate water from air on Earth's surface but rather the pull of gravity. Gravity pulls more strongly on the more dense water, so the water goes down and pulls together to 'push' the air upward.

No gravity, no pull...no buoyancy...no separation.

How cool is that?

WashU Expert: The global helium shortage hits home

Source - https://www.thoughtco.com/why-do-helium-balloons-deflate-4101553

It's been a decade or more since I first started hearing about a pending helium shortage.

But I didn't notice anything since then.

Sure, Party City posted something about the helium shortage, but I can't remember that last time I bought a helium balloon. I don't care about Party City being able to fill balloon orders or not.

We don't, admittedly have the most reliable helium 'production' system.

Three main sources produce some 75 percent of the world’s helium — sites in Qatar, Wyoming and Texas — > according to gas industry publication Gasworld. In fact the U.S. has for decades provided much of the world’s supply (from cnbc.com)

...and...

A versatile gas, helium is primarily used in electronics and semiconductor manufacturing and is particularly important for medical imaging, such as magnetic resonance imaging (MRI).

Helium is used as a cooling agent in MRIs and in manufacturing processes. Because helium is stable and does not react with other elements, it is also used in the making of semiconductors to create a contamination-free environment.

Still, the biggest consumer use of the gas is in party supplies — and that area is being hit especially hard by the shortage. (again, cnbc.com)

...

[A]nywhere between 50 and 200 of Party City’s 850 stores don’t have any helium in their tanks at any given time. (again, cnbc.com)

As I write this, Party City has announced the closing of 45 stores nationwide, including the one nearest Princeton High School, but we're going to be out a lot more than party balloons in the scientific realm unless we can either produce more helium (an unlikely outcome based on what I know about noble gases) or use it more efficiently.

Source - https://boingboing.net/2019/05/10/helium-shortage-deflating-part.html

As with so many things, I blame Cleveland.

World's Lightest Solid!

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.

---

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.

Red Cabbage Chemistry - Sick Science! #105

...but the smell...

If you don't want to buy universal indicator, make yourself some red cabbage solution. It's cheaper. It's available at your local grocery store.

And it smells like cabbage.

You can - if you're a school - also buy cabbage extract powder from some science suppliers.

It's a great way to pass an afternoon...or just to entertain yourself while your significant other makes red cabbage to go along with the smoked sausages if you - like I - don't eat cabbage.

Results after the jump...in case you're too lazy to do the experiment yourself...

Revealing Van Gogh's True Colors

Current version (left) and digitally recolored version (right) from the SciFri story.

I have to confess that I hate Science Friday.

I like the idea of a weekly hour of science content on NPR, but I can't stand Ira Flatow. He's obnoxiously curious, interrupts his guests with inane questions, and just generally annoys the crap out of me. I prefer the show when he has a substitute host.

That being said, sometimes the guests have fascinating things to say. On this episode, Ira interviews the senior conservation scientist at the Art Institute of Chicago.

It's fascinating that the painting has faded with exposure to oxygen and light exposure and that Van Gogh knew this - not that he knew the chemistry but that he was aware of the fading of the paints overtime and painted in a way to allow for that.