An excellent video on methane by the Periodic Table of Videos crew last month.
Safety Note: Samantha “Pants!” Tang is not wearing a lab coat, gloves, and her hair is not fully pulled back.

Also from the Periodic Table of Videos, Sam shows us the Traffic Lights reaction.
Safety Note: Sam does not wear gloves even while working with NaOH powder.
EH&S Note: Throws the solution down the sink.

Mitch

Who knew boiling a liquid was so complicated?  When you put a pot of water on the stove or heat your reaction-in-toluene solution in an oil bath several things happen.  The liquid closest to the heating element starts to get hot.  Convection circulates the hot liquid up and the cold liquid down due to the density differences of hot and cold liquids.  Eventually, the liquid near the heating element becomes hot enough to move into the vapor phase and bubbles start to form.  Buoyancy causes the bubbles to float to the surface and pop, while more convection continues to circulate the water.  Eventually, you get a rolling boil.

Everything changes in the microgravity environment of space.  Buoyancy and convection no longer play a role.  The heated fluids no longer circulate and the bubbles no longer naturally rise to the surface.  So what happens when you try to heat a liquid to boil in microgravity?  Astronauts tested this during the course of several space shuttle missions during the 1990s.  They arrived at some very interesting conclusions.

First, the liquid nearest the heating element starts to get hot, just as it does on Earth.  But it doesn’t rise and circulate due to convection.  It just gets hotter and stays next to the heating element.  It eventually gets hot enough to move into the vapor phase, just as it does on Earth, but the bubbles don’t rise to the surface and pop.  Instead, they stay next to the heating element and coalesce into one giant bubble.  Eventually, the size of the bubble becomes larger than the heating element and there is no longer any liquid in contact with the heating element.  This insulates the liquid from the heating element and leads to a “dry out” where there is no more boiling and the temperature of the heating element “begins to soar.”

(click on the image to go to the NASA page describing Zero G Boiling and to see an awesome movie of boiling in action)

All of this is predicted by theory, but it’s nice to have the chance to do some of those proof of principle experiments for the first time ever.  It reminds me of what some of the pioneers of science must have felt when working out some of the fundamental theories of chemistry and physics that we don’t even realize we take for granted today.

An interesting variation of this experiment was conducted impromptu by an astronaut on the International Space Station in 2003.  Don Pettit* was performing repair operations using a soldering iron.  He decided to put a few milliliters of water on the hot surface.  The water droplet formed a blob around the soldering iron and kinda wobbled there.  As expected, the water heated up and began to boil.  Surprisingly, though, this time the boiling looked much similar to boiling on Earth.

My working theory is the small amount of water and the inherent jostling of the system (the soldering iron looks like it was held by hand in front of the camera) caused enough motion in the water to move the bubbles around.  The bubbles could bump into each other and coalesce.  The size of the bubbles quickly reached the surface (unlike the bulk boiling experiment described above) and were allowed to pop.  Thus, it is by accident, in my opinion, that the boiling looks like it would on Earth.  It’d be interesting to repeat the experiment with the soldering iron held steady by vice grips or something.

(click on the image to go to the NASA page on the soldering iron boiling experiment and to see an awesome movie of this microgravity microboiling in action)

Here’s an overview page of boiling in space.
Here’s the NASA page on the 1990s boiling experiments.
Here’s the NASA page on the impromptu soldering iron boiling experiment.

*Also inventor of the super awesome zero-g coffee mug.

Jonathan Howse

The current state of the art in nanopropulsion devices was recently reviewed by Ebbens and Howse in an article last Friday.^[SoftMatter] A short summary of the nano- systems is presented below with video action shots when I could find them.

The Whitesides

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Bubble propulsion
Terrain: Aqueous meniscus
Max Speed: 2 cm/s
Mitch’s Name: The Karl Benz (since it was the first)
Article: Autonomous Movement and Self-Assembly

The Sen-Mallouk-Crespi

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Self electrophoresis/Interfacial tension
Terrain: Settled near boundary in aqueous solution
Max Speed: 6.6 um/s
Mitch’s Names: The Ford Mustang of nanopropulsion. (It is a hot rod, get it?)
Article: Catalytic Nanomotors: Autonomous Movement of Striped Nanorods

The Jones-Golestanian

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Pure self diffusiophoresis
Terrain: Free aqueous solution
Max Speed: 3um/s
Mitch’s Name: The Volkswagen Beetle
Article: Self-Motile Colloidal Particles: From Directed Propulsion to Random Walk

The Mano-Heller

Catalyst: Glucose oxidase and Biliruben oxidase
Fuel: Glucose
Propulsion: Self electrophoresis
Terrain: Aqueous meniscus
Max Speed: 1 cm/s
Mitch’s Name: The Komatsu Truck (because it is huge)
Article: Bioelectrochemical Propulsion

The Feringa

Catalyst: Synthetic catalse
Fuel: H₂O₂
Propulsion: Bubble/interfacial
Terrain: Acetonitrile solution
Max Speed: 35 um/s
Mitch’s Name: The F150 (has some exhaust issues)
Article: Catalytic molecular motors: fuelling autonomous movement by a surface bound synthetic manganese catalase

The Sen-Mallouk

Catalyst: Pt (CNT) (+cathodic reactions at Au)
Fuel: H2O2/N2H4
Propulsion: Self electrophoresis
Terrain: Settled near boundary in aqueous solution
Max Speed: 200 um/s
Mitch’s Names: The Ford Mustang GT (has more kick than the regular version)
Article: Bipolar Electrochemical Mechanism for the Propulsion of Catalytic Nanomotors in Hydrogen Peroxide Solutions

The Feringa v2

Catalyst: Glucose oxidase and catalse
Fuel: Glucose
Propulsion: Local oxygen bubble formation
Terrain: Free aqueous buffer solution
Max Speed: 0.2–0.8 um/s
Mitch’s Name: The Chevrolet Nova (more hot rod action)
Article: Autonomous propulsion of carbon nanotubes powered by a multienzyme ensemble

The Gibbs-Zhao

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Bubble release mechanism
Terrain: Aqueous solution
Max Speed: 6 um/s
Mitch’s Name: The Rover
Article: Autonomously motile catalytic nanomotors by bubble propulsion

The Bibette

Engine: External magnetic field
Propulsion: Flagella
Terrain: Aqueous solution
Max Speed: unknown
Mitch’s name: The BMW Mini E (because there is no such thing as a magnetic car)
Article: Microscopic artificial swimmers

The Sagués

Engine: External magnetic field
Propulsion: Doublet rotation coupling with boundary interactions
Terrain: Settled near boundary in aqueous solution
Max Speed: 3.2 um/s
Mitch’s Name: The Smart ED
Article: Magnetically Actuated Colloidal Microswimmers

The Fischer

Engine: External magnetic field
Propulsion: Propeller drive
Terrain: Aqueous solution
Max Speed: 40 um/s
Mitch’s Name:
Article: Controlled Propulsion of Artificial Magnetic Nanostructured Propellers

The Najafi-Golestanian

Engine: Conformation changes in linking units
Propulsion: Time irreversible translations
Terrain: Free solution
Max Speed: ?
Mitch’s Name: The Eternal Concept Car
Article: Propulsion at low Reynolds number

Some devices that were not included by the authors of the review article, but should definitely be included in any list like this are below:

The Gracias

Engine: External magnetic field
Propulsion: Brute Force
Terrain: Aqueous solution
Max Speed: ?
Mitch’s Name: The Truck Cranes
Article: Tetherless thermobiochemically actuated microgrippers

Tetherless Microgrippers Grabs Tissue Sample – Watch today’s top amazing videos here

The Nelson

Engine: External electromagnetic fields
Propulsion: Flagella
Terrain: ?
Max Speed: 18 um/s
Mitch’s Name: The Tesla Roadster (simply awesome)
Article: Characterizing the Swimming Properties of Artificial Bacterial Flagella

Artificial Sperm – Watch more funny videos here

Link to Review Article: In pursuit of propulsion at the nanoscale

Mitch

Mitch

Edit: Various other topics they talk about in the upcoming episodes.. superconductivity, carbon nanotubes, Bose-Einstein condensates, magnetism, paramagnetism, and superfluidity with Helium II. I’m serious, this is a kid’s show. I am in love.

Although chemists don’t have a chemistry rock star, Youtube has made Martyn Poliakoff as close as we’ll get. Unless someone is bold enough to go the Paris Hilton route.

Safety Note: The cake baker, Samantha Tang, has no gloves on although she has a lovely accent and introduces me to a new interjection, “Pants!” In the background there are other lab workers without lab coats and their personal protective equipment.

Phil first covered the website earlier this year: The Periodic Table of Videos

Mitch

The video was made by Christopher Hendryx as his thesis for Ringling College of Art & Design.
Link: http://vimeo.com/4433312

Mitch

6 pages of video after video of chemistry demonstrations.  You’ll never get bored!

Kent’s Chemical Demonstrations Movies

Last lab of the semester today. Next week is the lab final and checkout. This week the students practiced column chromatography. They purified their crude product mixture from last week’s nitration lab. I’ve talked about the theory behind column chromatography before, so I won’t rehash it here in any detail. Suffice it to say that different organic compounds have differing affinities for a stationary phase versus a mobile phase. These differing affinities allow for one compound of interest to be separated from a mixture through the use of column chromatography. Students were aided this week in that their product was bright yellow. They could physically watch it run down the column, then only collect the yellow fractions.

Last lab of the semester means last demo of the semester.  This one’s a do-it-yourself demo, if you’d like.  You can separate the colors contained in M&M shells (or Skittles, or Reese’s Pieces, or Sharpies, etc) through chromatography.  I got my M&M proceedure here.  If you’re interested, other proceedures are available here, and here.   Basic rundown: put drops of water on wax paper, and put a piece of candy on each drop.  Allow for the water to strip the color off the colorful candy shell.  Cut a coffee filter into a rectangle.  Use a toothpick to spot each color onto the coffee filter.  Put the coffee filter into a 1% solution of table salt and allow the water to rise through the coffee filter.  Watch the colors separate like magic!

Couple’a observations I noticed.  Quite interestingly… the stationary phase matters.  A lot.  I started by spotting the colors on my silica gel TLC plates .  I was quite disappointed because the red and yellow both travelled with the solvent front and there was little separation.  I tried several different solvents… no luck.  I also noticed that according to the websites I was looking at, red should have travel the shortest distance.  Then I switched over to filter paper, and all of a sudden I got the results I was expecting.  Who knew?  Also, you should put a crease in the coffee filter before placing it in the solvent.  The paper will start to buckle and it will droop and fall over if it is not creased first.  The more distance you give the colors to separate, the better the results.  I used the largest filter paper we had, and ran the chromatograph twice to get the results shown.

Pop quiz, hot shot: Do you know what the difference between Red 40 and Red 40 Lake are?  I didn’t either.  Turns out… nothing.  At least, not as far as the compound responsible for the hue is concerned.  It’s all in the formulation:

Color additives are available for use in food as either “dyes” or “lakes”.

Dyes dissolve in water, but are not soluble in oil. Dyes are manufactured as powders, granules, liquids or other special purpose forms. They can be used in beverages, dry mixes, baked goods, confections, dairy products, pet foods and a variety of other products. Dyes also have side effects which lakes do not, including the fact that large amounts of dyes ingested can color stools.

Lakes are the combination of dyes and insoluble material. Lakes tint by dispersion. Lakes are not oil soluble, but are oil dispersible. Lakes are more stable than dyes and are ideal for coloring products containing fats and oils or items lacking sufficient moisture to dissolve dyes. Typical uses include coated tablets, cake and donut mixes, hard candies and chewing gums, lipsticks, soaps, shampoos, talc, etc.

There are 5 food coloring agents in M&Ms: Red 40, Yellow 5, Yellow 6, Blue 1, and Blue 2.  As you might expect, green separates into blue and yellow, but surprising the red and yellow of the orange M&M do not separate.  Rather, there is one orange spot with a larger Rf than red.  Brown separates to blue, red and orange.   But it looks like the blue in the blue M&M is a different blue than the blue in the green and brown M&M.

I’ve got lots of pictures from my experience (click for larger).  Note how poorly silica works and how different the Rf’s are between silica and filter paper.  the video is of separating components of felt tip pens, but it’s also neat.

There are no more demos planned, since the lab course is over.  Hope you enjoyed my miniseries.