Frost flowers

I've been in northeastern Wisconsin during a cold snap that came in rather quickly and I have been seeing "frost flowers" on ice on creeks and (formerly) wet rocks.  A more sophisticated description is given here on Wikipedia: http://en.wikipedia.org/wiki/Frost_flower_%28sea_ice%29 (see also the Hoarfrost Crystals post from 11/29/13).

Borax Snowflakes

(Originally posted 12-11-14; updated 12-25-14) Last night some Bradley students and I made borax holiday decorations, made by placing a template shape into a hot solution of borax.  When the solution cools, the solubility of the borax decreases and the borax crystallizes onto the template to make a sparkling structure.  Caution: Borax solutions are basic, and do not ingest borax.

To make the decorations, first make a wireframe shape from pipe cleaners.  Snowflakes are the most common, using white pipe cleaners, but other shapes and other colors can certainly be used.  One of my favorite variations  a sort of green spiral cone with beads on it to make a Christmas tree shape.

The concentration of borax that I use is what I have encountered on various websites: three tablespoons of borax per cup of water.  Heat the borax and water in a metal saucepan to make sure the borax dissolves.  Be careful working with the hot borax solution. For example: do not heat the solution in a jar directly on the heat source - I broke a jar on a hot plate trying that.  The wireframe shapes can be hung from sticks placed over the openings of glass canning jars.  Make sure the shape can fit in and out of the jar without squishing the shape (remember when the process is done the shape will be covered with about a half centimeter of brittle crystals).   Keep the shape about three centimeters from the bottom of the jar - that is where the excess crystals tend to accumulate and they can stick the shape to the bottom of the jar. Note that the large snowflake in the pictures below was not made in a jar but rather by mounting the shape horizontally in the solution in the saucepan.

Carefully pour the hot borax solution into the jars, making sure to cover all surfaces of the wireframe shapes that you want to cover with crystals.  Let the solutions cool to room temperature, and we found that we had to cool the solutions still further to a few degrees Celsius overnight (either outside or in a refrigerated room) in order to get a good coating of crystals.

After the crystals are grown, remove the wireframe shapes from the jars and blot away extra solution with paper towels.  The crystals of borax are shiny and translucent at first, but over the course of months they will become cloudy and chalky.  Remember to keep kids and pets from ingesting the borax from your crystalline creations.

UPDATE 12-25-14: I took some leftover warm borax solution and used it to deposit crystals on styrofoam balls.  The hard part was devising a way to submerge the balls, but the crystals did deposit (though not so much at the point they were being held submerged).  We stacked the balls and decorated them to make sparkly snowmen (last picture below).  Have a blessed Christmas!

Dust Can Explosion Gone Awry

Many websites have described the classic dust can explosion demonstration.  Essentially, a closed metal paint can is fitted with a device to blow a fine powder throughout its interior.  Lycopodium powder is often used as the powder, and a squeeze bulb is often used to blow the powder around.  The dispersed powder is ignited by a lit candle that is also in the paint can during the demonstration, and the combustion of the powder produces sufficient heat and pressure to blow the lid off the paint can.

I have not done this demonstration much, but it was a favorite of one of my colleagues, professor Max Taylor, who was a talented demonstrator at Bradley University.  When he passed away last month, I dug out his old dust can explosion demonstration.  I successfully blew the lid off the paint can, but one time when I did so, the lid went up with the flame outburst and then back down to seal on top of the can.  Instantly the can collapsed as the gases inside the can cooled and contracted.  Looks like Max Taylor left some big shoes to fill!  I have rebuilt the demonstration with a different paint can.  In the future I will work to make sure the lid is blown clear of the can.

A Tile Puzzle Analogy of Electrons and Holes in Semiconductors

Holes in semiconductors can be described as locations where valence electrons are missing. These holes can move in one direction as a result of the electrons moving in the opposite direction.  An analogy I have used in my classes is the sliding tile puzzle: as the tiles move one way, the "hole" from the missing tile moves in the opposite direction.  Inspired by this concept, I adapted one of these tile puzzles to illustrate my point.

Hygroscopic Iron(III) Chloride Hydrate

I have found over the years that iron(III) chloride hydrate can be pretty hygroscopic.  Here is a vial that once contained the dry salt, but has picked up plenty of moisture over time.  This seems like a more safe compound to demonstrate hygroscopic behavior than, say, solid sodium hydroxide.

Expansion of Water as It Freezes

There are lots of demonstrations showing the expansion of water when it freezes (and demonstrating hydrogen bonding and molecular geometry), but the demos do not need to terribly sophisticated.  Here is what happened when I left a full water bottle in a cold car overnight.

Blackbody Radiation with an Incandescent Bulb on a Dimmer Switch

The camera does not show this as well as the eyes, but I thought this incandescent bulb was a good qualitative example of black body radiation.  As I turned the lamp switch from dimmer to brighter, the relative intensities of shorter wavelengths of light increased.  The net result is that the relatively cool dim bulb appeared reddish and the relatively hot bulb appeared yellow or white as more blue light was mixed into the glow.

Illinois Heartland Anniversary Celebration

Yesterday, the Illinois Heartland Local Section of the American Chemical Society celebrated its 75th anniversary with a poster session, dinner, and lecture.

Guess Who Game with Elements

I was watching my kids play Guess Who today and I was thinking about an upcoming lab that we need to develop involving the elements when it dawned on me that one could do the Guess Who game with the elements.  I got excited about the idea, and then a family member found a very impressive version published by Natalie Gillis online at: http://mizgillis.blogspot.com/2013/01/guess-who-periodic-table.html .  Looks pretty cool!

Real vs. fake thermal images

Yesterday, someone showed me the "thermal" setting on digital camera software on their laptop computer.  Although this setting somewhat emulates the colors of many infrared images, these are not truly infrared images.  I think all this setting does is take visible light intensity, like one would see in a grayscale image, and convert it to the colors commonly seen in infrared images.  Here are three pictures of me: in conventional color camera mode, in "thermal" mode on a laptop camera, and in an infrared image on an FLIR camera.  Two things to note in the FLIR camera picture is that my glasses appear dark because they are cooler than the skin of my face and the writing on my shirt is not visible because it is the same temperature as the rest of my shirt. Thanks to the Peoria Riverfront Museum for the loan of the FLIR camera.

Grand Valley State University Bifilar Pendulum

Today I gave a presentation at the 2014 Biennial Conference on Chemistry Education (BCCE) at Grand Valley State University.  Beforehand, I found this pendulum nearby which traces patterns in the sand below it. Though it is an excellent demonstration of pendulum motion, it is also known for its five minutes of infamy, as GVSU students tried to ride the ball in satire of the Miley Cyrus wrecking ball video.  Apparently students have done this before, but some of them were unclothed and someone almost got injured, so the ball got taken down while the installation was redesigned.  News about this can be found here: http://www.businessinsider.com/grand-valley-state-university-reinstalled-the-miley-cyrus-wrecking-ball-sculpture-2013-11

Sound Spectrum of a Pop Toob

Pop Toob (or Rapper Snapper) toys make sounds that readily show the relationship between the lengths of the Toobs and the frequencies of the noises that they make when they change shape. I used SpectrumView to acquire a waterfall spectrum of a Toob as it is stretched to full length and then squeezed back to its minimum length.  Reading the waterfall spectrum from the bottom upward, note the frequency maxima shift to lower frequency as the Toob is stretched, and then the maxima shift back toward higher frequency as the Toob is re-compressed.

Infrared Image of Warm-Blooded and Cold-Blooded Animals

This FLIR image was taken of warm-blooded people and a pygmy African hedgehog, as well as a cold-blooded corn snake.

Vernier Oxygen and Carbon Dioxide Sensors Around a Campfire

I slowly walked around the glowing coals of a campfire tonight while holding Vernier oxygen and carbon dioxide sensors at about hip level.  The highs in the carbon dioxide readings correspond to lows in the oxygen readings, and these highs and lows correspond to when I was roughly east of the fire.  Though the wind was almost calm, it appears to me that the "smoke" from the fire was blowing toward the east.   I think under much more controlled circumstances this could lead to classroom/laboratory exercises in mapping plumes of gases from point sources.

Heat Camera on Glow Sticks

I used an FLIR camera from a local museum to capture these images of hands holding glow sticks.  The images show how the chemiluminescence of the sticks is considered to be a relatively cold source of light. The hands glow more brightly in the IR image than do the sticks!

Softening Point of 2-Liter PET Soda Bottles

When exothermic demonstrations are performed using 2 L polyethylene terephthalate (PET) soda bottles, the bottles sometimes soften and shrink.  A great example of an exothermic reaction that can do this to PET bottles is the catalytic decomposition of 30% hydrogen peroxide.  Wikipedia has mentioned that the glass transition of PET is about 70 C, so we set out to check to see if that corresponded to the softening point of the PET bottles.  We heated a large kettle of water to various temperatures with a stove, checking the water temperature with a Vernier temperature probe.  At selected temperatures, we placed a 2 L PET bottle nearly completely into the water (with its opening above water and the interior NOT flooded with water) for one minute.  The results are shown in the picture below.  At 65 C the bottle is unchanged, but at roughly 70 C and above, the bottle deforms.  The extent of the bottle deformation seems to increase as the temperature increases. Thanks to Kristine Campbell for assistance with the experiment.

Slow Motion Mentos and Soda

Have not posted in while in part because I have been busy developing demos.  The addition of Mentos to soda is well known so I will not go into it in too much detail. Basically, the physical and chemical makeup of the shell of the Mentos helps the carbonation to quickly leave the soda, causing a fountain to rise up out of the bottle.  I have attached a slow-motion video taken by Karen Dismang (using an iPhone5s) of Ben Hendrix doing this demo.
 I have a couple comments:
1) Powdered Metamucil and other substances can cause soda to fizz  - although Mentos work really well.  Half of a roll of Mentos (seven candies) is enough to do the job. Not long before Mentos and soda was a "thing", it seemed that there were videos of ice cream and soda going around where someone would eat a bit of ice cream and then try to drink soda - perhaps similar chemistry?
2) Any soda or carbonated water should work.  The color of the fountain will depend on the color of the soda.  Tonic water fountains can be made to fluoresce with UV light (although one must be careful not to get the soda into the electrical fixtures).  For indoor demos, I recommend  using colorless soda, as I accidentally permanently stained a classroom ceiling tile with dark-colored soda. (Thankfully, the teacher thought it was funny.)
3) Use a diet soda.  Sugary sodas can be sticky to clean up.

Liquid Nitrogen Marshmallows

This evening I brought home a little liquid nitrogen and we added marshmallows that were cut into quarters.  The marshmallows soak up a little liquid nitrogen and become crunchy, almost like the marshmallows you find in cereal.  When you bite into the marshmallows, their coldness causes the moisture in your breath to condense and produce the appearance of steam as you chew them.  No need to use a full-sized marshmallow or just liquid nitrogen itself.  Too much cold shock to the mouth could crack a tooth.

Collecting Sap to Make Maple Syrup

Original post 3-20-14: The sap is running in our maple trees and I am collecting some to try to make maple syrup.  What an interesting exercise in working with colligative properties like boiling point elevation! I tried boiling down a little sap several years ago, but overshot the syrup stage to produce sugar.  To collect the sap, I drilled a hole in each tree to a depth of about 5-7 centimeters and angling somewhat upward into the tree.  For each spile, I used a (clean) plastic syringe and removed the plunger.  I cut the tip end off of the barrel with a razor blade, and then cut a sort of slit in the side of the barrel from the cut end until maybe a centimeter from the finger flange.  I inserted these spiles into the holes in the tree until only about a centimeter was showing (if you push too hard you might break the spile).  I oriented the finger flanges of each spile in a vertical position, which I used to wire on a one-gallon freezer bag with a zipper.  New post 4-13-14: I collected over 2 liters of sap (represented by the pitcher of water), which I boiled down to make about 100 mL of yummy maple syrup.  The whole process was fun, but it strikes me as quite energy intensive.

Glacial Movement

I an currently teaching a geology lab for the first time, which has its challenges, but I since I have been rockhounding as a hobby for much of my life it has also been fun and educational.  I have been looking at older topograpic maps and aerial photos of various alpine glaciers and comparing them to more recent information and found that while some of the world's glaciers have advanced, many have been retreating. The picture shows an aerial photo of a Alaskan glacier taken in the 1950's in comparison to a more recent image on Google Earth. This is one of those glaciers in retreat.

Whak-A-Pack Valentines

Around this time of the year a local dollar store sells four Valentines Day-themed Wack-A-Packs for a dollar.  These are fun chemistry demos!  Inside each pack (bottom right in picture) is a deflated polyester balloon.  In the balloon is powdered citric acid and powdered sodium hydrogen carbonate (upper left in picture - much like an Alka-Seltzer tablet) and a pouch filled with water (lower left).  When the pack is struck hard, the water pouch breaks, enabling the water to dissolve the acid and salt.  These react to produce carbon dioxide gas which causes the balloon to inflate (upper right) and pop out of the pouch. I recommend passing the balloons around the classroom as soon as they open, because for a little while, the reaction can be heard fizzing in the balloons as carbon dioxide continues to be produced, and the balloon feels cold (I attribute this to the enthalpy of solvation of the sodium hydrogen carbonate).

Spontaneous Assembly (or "Self Assembly") of Hot Dog Slices and Meatballs

Originally posted May 22, 2012:

Cut hot dogs into ~1 cm thick slices and place them in a pan of water. They will float at the water's surface and attractive capillary interactions will draw them together into an organized close-packed array.

References:

Dungey, K. E. J. Chem. Educ. 2000, 77, 618.

Campbell, D. J.; Freidinger, E. R.; Hastings, J. M.; Querns, M. K. "Spontaneous Assembly of Soda Straws." J. Chem. Educ., 2002, 79, 201.

Campbell, D. J.; Freidinger, E. R.; Querns, M. K. "Spontaneous Assembly of Magnetic LEGO® Bricks." The Chemical Educator, 2001, 6, 321.

Campbell, D. J.; Freidinger, E. R.; Hastings, J. M.; Querns, M. K. "Spontaneous Assembly of LEGO®s." Chem13 News, Sept., 2001, 8.

ABOVE LEFT: Cutting hot dogs into slices. ABOVE RIGHT: Floating them in a pan of water. Note: sometimes tapping the pan will help shake out some of the defects in the assembled pattern.

Updated January 22, 2014:

BELOW: Assembly of meatballs after being churned about in boiling water.

A Redneck "Bleeper"?

It seems that when I fire a piezoelectric grill lighter near my TV tuner, it interferes with the picture a little and cuts out the sound for a about one syllable's length of time.  Another lighter on another tuner seems to just make a brief horizontal line on the screen but not so effective with cutting the sound.  Must be some radio-frequency emission in that electrical pulse? The effect happened on the 3 channels I tried. I do not really have a picture for that experiment, so I will use this pic of a fiery demo. The Bradley University Chemistry Club Demo Crew had their 120th show on Wednesday.  Thank God, we finally reached the 10,000 customer mark.  I was acting as the spotter as a student squirted water into burning liquid wax. If overdone, the flames could probably hit the lecture hall ceiling.  

"Yogurt Lab" (not a demo)

My family and I were in Minneapolis, MN, this past Friday, and while we were exploring the skyway we found a frozen yogurt place called "Yogurt Lab."  It's part of a chain in Minnesota, see: http://www.yogurtlabs.com/. We enjoyed the snack and I loved the decor, especially the lamps that looked (but happily did not smell) like triethylamine molecules.

Very hot water in very cold air

During the present cold snap that is gripping much of the nation (-8 F for a high here in Peoria today), the Internet and other media outlets have been describing what happens when you toss near-boiling water into the very cold air.  Basically, the hot water breaks into fine droplets which instantly freeze to make an ice cloud, see: http://www.huffingtonpost.com/2014/01/04/boiling-water-extreme-cold-water-gun-ice-crystals_n_4538522.html?utm_hp_ref=mostpopular for more explanation.  I tried it, too, with cold water as a control experiment (no "cloud" was produced).  CAUTION: I have heard that people are burning themselves with hot water!  The air is not cold enough to freeze all of the water.  Throw the water away from you and downwind!