How the Demon Core Killed a Man in 9 Days

The demon core is a legendary sphere of plutonium gallium alloy that was designed to be - when encased in neutron reflectors like beryllium or tungsten - just a hair away from achieving critical mass and releasing massive amounts of radiation.

That idea of making something that is just a tiny accident away from releasing deadly anything was - in retrospect - perhaps a mistake. 

The demon core became known as such because of two deadly incidents, the second of which is retold in the above video, fictionalized in the below clip from the movie Fat Man and Little Boy, and more thoroughly examined in the third video from Kyle Hill.

Check all the videos out and maybe remember not to build a gun that shoots bullets out in every direction while giving it a hair trigger, eh?

The Unknow Phase of Matter

God lord but Steve Mould is a brilliant communicator of science.

I've never really understood super critical fluids - even though I've posted about them before, but today's video - especially the part from about 10:20 through 14:20 or so - makes for a brilliant explanation of why fluids go supercritical at higher temperatures.

The use of the entropy and potential energy graphs in combination lays out the argument for supercriticality brilliantly.

Thanks, Steve...thteve.

Why Lithium Is Dangerous But PERFECT For Batteries

Our chemistry book has a diagram of a battery in the electrochemistry chapter, and I discuss that battery for a bit before explaining to my students that the basics of ACME (anode, cathode, metallic path, electrolyte) hold for every battery but that the engineering of modern lithium-ion batteries is far different from the diagram in the book.

This video - again leaning into the algorithm-rewarded longer and longer format - explains some battery basics involving the activity series, the history of the development of the lithium-ion battery, and the methods of fiery failure when the battery overheats.

This is, as Dr Derek says, a technology that has allowed our modern, battery-dependent world.

I bought a freeze dryer so you don't have to

This guy does a lot of things that I don't think I should do.

My wife has, admittedly, suggested that she might be interested in buying a freeze dryer. It's not something that's come up more than once or twice, but it's been mentioned. 

Clearly buying a freeze dryer would be bonkers and nuts. We don't need it. The energy spent isn't remotely worth the very, very few times we'd ever use it before letting it sit unused in a closet somewhere.

At least that's my perspective on the thing, and clearly Mr. Technology Connections agrees with me.

Even though the science involved is kind of fascinating.

Light sucking flames look like magic

I've posted about this black fire on the blog before.

This one - from Steve Mould - doesn't add a whole lot new to the basic technique of shining a sodium vapor light on a methanol (stay safe out there, folks) flame that has been doped with sodium chloride. It does add in some more information on how the spectra are created and some info about enchroma glasses (more on them next week).

How cooks put their fingers in hot sauce without burning themselves

Heat =/= temperature

Temperature is the average kinetic energy of the particles in a substance.

Heat is energy transferred from one body to another due to a difference in temperature.

Hot things - like boiling water or simmering sauce - conduct energy to cool things - like your finger.

The amount of energy you get from that hot sauce depends on way more than the temperature of the sauce. More mass of sauce that you get on your finger means more molecules with that same average kinetic energy, so more total energy, so more pain.

In this video Adam switches mass out for time in contact with the sauce, but in this case that seems a fair swap.

Don't dunk your finger in hot fryer oil or hot sugar syrup. According to Adam, go ahead and dunk (or flick) your finger in hot, water- or oil-based sauces.

As always, vinegar leg on the right.

Reusable handwarmers that get hot by freezing

The title of this video is wrong.

There is no freezing happening. There is recrystallization happening from sodium acetate dissolved in solution.

That's not freezing - a pure liquid turning into a solid like ice turning into water. The host seems to understand that distinction, but he's sloppy on using the term freezing and freezing point somewhat misleadingly. He also is sloppy on liquid versus solution and melted versus dissolved.

Most of this video is an explanation and comparison of the two types of hand warmers - the reusable sodium acetate solution and the single-use iron rusting type. The video host explains the science behind what's happening and judges the single-use to be the better choice - something that I'll leave up to you.

I use both in class for different purposes and different chapters.

Energy transitions

@tomkovlebduka

♬ původní zvuk - Tomáš Kovář Lebduška

And it's just that simple, folks.

Turn a chunk of wood into kindling by bashing it pretty well.

Hit a steel rod with a hammer enough that you turn the kinetic energy of the hammer strikes into enough heat energy for the rod to glow red.

Then touch the red-hot steel rod against something combustible and low density like paper.

Use the paper to start the kindling and get some air flow going.

Easy peasy...

The chemistry of pyrotechnics (loooong)

Today you get four long videos about fireworks. The above is an episode of Nova from PBS on the history and chemistry of fireworks. I fully assume that I'll have to refind it eventually because Nova tends to be pretty good about deleting their episodes from YouTube when they're posted whole like this.

The chemistry of pyrotechnics (shorts)

After the fireworks video a couple of weeks ago, I went hunting more videos to explain the chemistry of pyrotechnics, and I found a bunch of them.

We'll start this week with the shorter videos.

The one above is the most comprehensive of the short (10 min or less) videos I've found. It explains a bit of history, some of the structure of, the chemical reactions taking place in, and the colors produced in common fireworks.

Start with that one. 

It isn't, however, a very pretty video. It's a lecture with an animated hand writing and drawing on a digital white board. Not the most exciting of the videos.

Can you light a match with water?

My first teaching job was at Terre Haute South Vigo High School in Terre Haute, Indiana.

At THS (we pretty much just called it Terre Haute South), one of the other science teachers gave me a coiled copper tube that looks pretty much like what's shown in the video and was used for exactly what it's used for in the video.

I think I set the demonstration up once...maybe twice ever...and had that copper tube in my storage drawers at three separate schools. I can't remember offhand whether I brought it over to the new building. I think I'll check, though.

But, that's not what the video is about. The video shows how water can be heated to vapor which can then be superheated to a high enough temperature to set a match aflame.

The video also goes on to explain why the copper corrodes so thoroughly.

Kind of cool neat.

Phase Change Materials. wmv

I remember the Cincinnati Bengal mascot coming to our school a decade or so ago, back when Becky and I were running the Pasta for Pennies campaign (and raising $30K-40K in a month doncha know). He was there for what we called the Wacky Olympics, a celebratory picnic and bunch of games that we held at the end of our fundraising year. We would have grade-level (and staff) teams compete in stupid games (pass the orange, four-legged race, stuff like that), eat hot dogs, drink punch, and generally have a blast.

One year the local Leukemia and Lymphoma Society chapter arranged for the Bengal mascot to come out and celebrate with our students. It happened to be a nice, 85-degree day, though, so I was a little worried that our mascot would end up with heatstroke. He explained to me that he had 'ice packs' that weren't really ice under his costume. Those packs were filled with a material that undergoes a phase change from solid to liquid at around 70^oF, meaning that they'll have a stable temperature at that range for a long time, keeping the mascot-suit-wearing human close to that temperature for a long time.

The video up top shows a material similar to that being used in wall materials to keep the office at a fairly stable 23^oC (73.4^oF).

The videos below show something a little more like what the mascot wore under his costume.







How cool is that?

Nitromethane Jet Bottle - Looks Awesome in 4k Slow Motion - aka Whoosh Bottle

The whoosh bottle is among my favorite demonstrations.

It's easy as pie to set up. It allows some phenomenal chemistry to be shown (limiting reactants, combustion, exothermic reactions, energy transfer).

And it looks gorgeous.

I'm not sure that the nitromethane woosh bottle adds anything cool, but the slow-mo, 4K video definitely does.

How Is Black Fire Made?

TL;DW - it involves sacrificing a virginal chemistry student to the chemistry gods...

jk

Actually, this one's pretty brilliant. It's the distinction between emission and absorption spectra.

See, when the yellow light is produced (or emitted) - as shown around 1:00 in the video - it's because electrons are bouncing up and down within the atom (as shown via a Bohr model). That's an emission spectrum.

That requires energy. In the fire that energy comes from the chemical reaction of the ethanol (remember kids, no methanol) with oxygen...burning.

When the sodium vapor light is on, however, it's providing exactly the right amount of energy to excite those electrons. Which is then absorbed by the sodium atoms in the flame, leaving behind no light at all. That's an absorption spectrum.

And that's so cool...

Why I changed my mind about nuclear power | Michael Shellenberger | TEDxBerlin

I'm shocked...

Like stunned...

I grew up in a firmly anti-nuke, Gerry Brown kinda household. My mom swears I didn't eat a grape until I was like five years old because she wasn't going to support the farmers against the migrant workers. There was always Bob Dylan playing on the record players, and nukes were nothing but death in waiting.

And nukes meant both nuclear weapons and nuclear power.

I remember visiting Marble Hill - a never-operational nuclear power plant in Southern Indiana - either during high school or college, and it freaked me out because nuclear power - which very nearly came to that power plant just an hour from my home - was a practical demon in a bottle. I'm pretty sure that my mom was one of the folks protesting against Marble Hill's construction in the early 1980s.

But it looks like my mom just might've been wrong.

The video shown above presents pretty strong evidence that nuclear power might be the better alternative to solar or wind power.

I'm going to have to do some more research.

And the video below - also from Michael Shellenberger, who appears to have a decent number of bona fides - tells the story of how nuclear power shifted from being an environmentalist's darling to being everybody's boogeyman.

What is Fire?

Fire is awesome.

That's a simple enough answer, isn't it?

This video - with its oddly-voiced, slightly-speech-impedimented (or maybe just a British accent), and weird narrator - explains a bit of the history of elements and then goes through the parts that really make up the fire: fuel, gas, light, heat.

In the end, the answer to the video's titular question is this: Fire is actually the visible side effect of what happens when matter undergoes a change of state by means of a chemical reaction. (at 1:15 in the video)

Fundamentals of Science: Heat versus Temperature

Heat and temperature are not the same thing.

Man, if I could get 100% of my students to understand that distinction, I would feel like my themochemistry units were fairly successful.

Yeah, there are other details here and there, but really, that's a pretty big idea right there. Heat and temperature are not the same thing.

Serious Eats just put out a cookbook under their The Food Lab label, and one of the introductory chapters - specifically the one dealing with this heat/temperature distinction - is available for free online.

They, of course, focus on what that distinction means for cooking...

The article goes through the methods of heat transfer: radiation, convection, and conduction.

They also discuss some differences in cooking vessel material, specific heat and heat capacity, and relevant reference temps (for freezing, boiling, and germ killing). Plus they describe an experiment to show the difference in energy transfer rates between water convection (a pot of cold water heating to boiling) and air convection (a 200 Fahrenheit oven), both of which are tested with your hand and a thermometer.

From the article's finale...

To sum up:

• At a given temperature, denser materials generally contain more energy, and so heavier pans will cook food faster. (Conversely, it takes more energy to raise denser materials to a certain temperature.)
• At a given temperature, materials with a higher specific heat capacity will contain more energy. (Conversely, the higher the specific heat capacity of a material, the more energy it takes to bring it to a certain temperature.)