How should you observe a demonstration involving an explosion?

AB

CD

EFG

If you picked "C" you are correct. In this position the shock wave of the explosion will be deflected by your hands, yet you will still be able hear other sounds in the room, like the voice of the person giving the demonstrations. Source: Dr. John Fortman in a presentation at Bradley University.

Alcohol Rocket Car (exothermic combustion of alcohol)

Put wheels on a milk jug and alcohol vapor inside, then light the end and away it goes! Special thanks to Wayne Bosma at Bradley University for introducing me to the classic alcohol "whoosh" bottle. LEFT: The rocket car at the Bradley University High School Chemistry Contest in 2009.  MIDDLE: The rocket car at Demos on the Lawn '99 in Madison, Wisconsin. RIGHT: This melted jug might be what happens to the rocket car if you don't see the related paper in the Journal of Chemical Education.  I have recently developed a sturdier car construction than the one published in JCE.

Chelate Effect with a Bag Closure

(first posted elsewhwere on my websites on 3-18-12)

 

Polydentate ("chelating") ligands have more than one point of connection to a metal center and tend to bind more strongly to those metals than monodentate ligands (which only have more than one point of connection). This can be illustrated with a plastic bag closure (see: http://www.kwiklok.com/kwik-lok-bag-closures.php). The two hook-like edges of the closure hold the bag closed more effectively than half a closure, which has only one hook.

 

ABOVE: The two hook-like edges of a bag closure (LEFT) hold the bag closed more effectively than half a closure, which has only one hook (RIGHT).

Turning Off Glowing Toys

(first posted elsewhere on my websites on 12-4-11)

Most glow-in-the-dark toys glow green due to zinc sulfide doped with elements such as copper. In about 1998, I was playing with a red laser pointer and some powdered doped zinc sulfide phosphor and found that the red laser cannot stimulate the phosphor to glow. The red light did not have enough energy to promote the phosphor electrons to the excited state. However, when the phosphor was already excited and glowing green and then was irradiated with the red laser the phosphor briefly glowed more brightly, and then darkened. I could use the red laser to draw lines of darkeness on the glowing doped zinc sulfide. I have found over the years that this stimulated emission and darkening phenomenon works using red light on other glow-in-the-dark objects, including glowing drawing screens sold by toy companies or the glowing screens at museums that record people's shadows from a light flash. I think this ability to use light to draw dark areas or lines on glowing objects could be used to enhance the utility/enjoyment of these materials. I would like to know more details about the mechanisms behind this phenomenon and welcome any insights that you might have.

ABOVE: A glow-in-the-dark butterfly shape gives a butterfly-shaped glow (LEFT), but when irradiated with a red laser pointer on the middle the glow is darkened (MIDDLE) or irradiated with a red laser pointer on the left wing the glow is darkened (RIGHT). Sorry the pictures are so faint - the glow was difficult to capture with my camera and you might have to adjust the angle of your viewing screen.

Balloon Effusion (Gas Laws)

 

ABOVE: (LEFT) Balloons initially filled to the same volume with nitrogen and helium gases. (RIGHT) Helium gas (4 g/mol) leaves its balloon faster than nitrogen gas leaves its balloon (28 g/mol).

Electron Microscopy of a Cracked Dried Film (Original)

Thought this looked neat.  The picture containing some added colors and lens flares is in my personal blog: Pix of the Day and Stuff: http://pixofthedayandstuff.blogspot.com/

Geckos and Nanotechnology

Here in Austin, Texas, it is not that unusual to see an occasional gecko - caught one last night. Gecko feet have an amazing ability to stick on-demand to a variety of surfaces – even glass!  Their climbing ability appears to be related to hair-like structures on their toes (one of the gecko's feet are in the lower right hand corner of the picture). Those “hairs” split and end in tips that are only about 200 nanometers across. To view the individual hairs, you would need a powerful electron microscope.  Scientists have learned how to generate textured surfaces that act like gecko’s feet and have even built robots with “gecko-inspired feet” that can climb up walls.

Balloon/Closed Bag in an Airplane (air pressure)

Most everyone who has traveled on an airplane has witnessed some effects of decreased air pressure in the cabin of the plane: ears "pop", poured soda fizzes a little more, and sealed bags swell up. This last observed phenomenon was the basis of a simple experiment run on a long flight from Chicago to Honolulu to estimate the amount of air pressure change. The equipment required is very simple: a typical rubber balloon, a flexible measuring tape (such as one used for clothing measurements), and a permanent felt-tip marker. All of this should present no risk to airline security. Before the plane leaves the ground, inflate the balloon about halfway. DO NOT fully inflate the balloon. If it expands too much when the plane is in the air, the ballon may pop. This not only ruins the experiment, but it may also disturb fellow travel-weary passengers. The flexible measuring tape is used to measure the circumference of the balloon. Since most balloons are not perfectly spherical it is advisable to use the marker to indicate the path of the measuring tape. That way later measurements can be made across the same path. Once set up, the balloon circumference can be measured at any time. On the Chicago to Honolulu trip, a ground circumference was measured to be 52.4 cm and a cruising altitude circumference was measured to be 54.9 cm. Assuming a spherical balloon and that the ground pressure was 1.00 atm, the pressure at cruising altitude would be 0.869 atm.

Using the relationship between altitude and pressure described on p.26 of van Loon and Duffy (van Loon, G. W.; Duffy, S. J. Environmental Chemistry: A Global Perspective, Oxford University Press, 2000), a pressure of 0.869 atm relative to a sea-level pressure of 1.00 atm corresponds to an altitude of 4000 feet. Most planes I have been on cruise at a around 35,000 feet, which corresponds to a pressure of 0.294 atm relative to a sea-level pressure of 1.00 atm. Clearly the cabin of the plane is pressurized!

ABOVE: Sealed roll package on an airplane (FIRST) at ground level and (SECOND) in the air.

Transparent Metal - A Future Goal?

Very thin metal films can transmit light, but they are not at all very strong.  It would be nice to have a transparent material with the mechanical properties of a bulk metal.  Science fiction works have noted this:  Star Wars novels refer to "transparisteel" (http://starwars.wikia.com/wiki/Transparisteel), and of course, the movie Star Trek IV made reference to "transparent aluminum" (for the scene, see: http://www.youtube.com/watch?v=JSmGjB-G6v8).

Liquidmetal Alloy

A recent news report describes the potential use of the amorphous metal alloy known as Liquidmetal for use in iPhone casings: http://www.cnn.com/2012/04/19/tech/mobile/liquidmetal-iphone-casing/index.html?hpt=hp_t2.  More details about this noncrystalline, hard alloy can be found at: http://en.wikipedia.org/wiki/Liquidmetal.  The alloy is quite hard; a ball bearing dropped on the alloy will rebound to a much greater height than one dropped on stainless steel, for the demonstration see the middle movie at: http://www.liquidmetal.com/resources/.

Demonstrating Poisson's Ratios with Chicken Wire

The lateral expansion or contraction of a material as it is stretched can be bescribed by a mathematical relation called the Poisson's ratio. Most materials tend to contract laterally as they are stretched (and have a positive Poisson's ratio), but some materials expand laterally as they are stretched (and have a negative Poisson's ratio). Often a material that has a positive Poisson's ratio can be modified to form a structure that has a negative Poisson's ratio. Chicken wire can be used to demostrate these ratios. Caution: Cut chicken wire can be sharp!

References:

Campbell, D. J.;Querns, M. K. "Using Paper Cutouts to Illustrate Poisson's Ratio." J. Chem. Educ., 2002, 79, 76.

For instructions on how to make fullerene models out of chicken wire, see Murphy, C. J.; Campbell, D. J. "A Chicken Wire Buckyball." Chem. Educator 2000, 5, 1.

ABOVE: Positive Poisson's ratio structures (LEFT) unstreched and (RIGHT) stretched.

ABOVE: Negative Poisson's ratio structures (LEFT) unstreched and (RIGHT) stretched.

No Suds! (water hardness)

This is an easy demonstration if you live in a place like the Midwest where hard water is readily available. Acquire some empty 20 oz. soda bottles and fill them halfway: one with hard water, one with deionized water. Add the same amount of soap to both bottle (several drops of inexpensive pine cleaner has worked for me, Ivory soap shavings also work well) and close the lids tightly on the bottles. Shake both bottles about 50 times. Immediately after shaking, the hard water will have more foam on its surface, but this foam quickly breaks, leaving only foam on the deionized (DI) water. The lack of foam on the hard water is due the calcium and/or magnesium ions in the water. These ions bind to the soap molecules in the water, rendering them useless. One result of this is that little or no foam forms on the surface of the water.

References:

Soriano, David S.; Draeger, Jon A. A water treatment experiment (chemical hardness) for nonscience majors. J. Chem Educ. 1993 70 414.

Birch, E. John H. Hardness in water- a demonstration. J. Chem Educ. 1949 26 196.

 

Ytterby Mine

A Bradley Chemistry and  Biochemistry major studied in Sweden in Spring, 2011, and visited the Ytterby mine.  The rocks from this mine were the source of four elements that were new to science.

Element Displays at the UT Chemistry Building

The first pic is of a lecture hall/seminar room ceiling in Welch Hall at the University of Texas at Austin.  There are Texas Longhorn motifs in the patterns, and along the main beams there are alchemical symbols - seven of the eight are related to celestial symbols (see: http://en.wikipedia.org/wiki/Alchemical_symbol):

gold (Sun)

mercury (Mercury)

copper (Venus)

antimony (Earth)

iron (Mars)

tin (Jupiter)

lead (Saturn)

sulfur (no connection - maybe it should be for Jupiter's moon Io - http://en.wikipedia.org/wiki/Io_(moon))

The second pic is of a large periodic table done in chalk under a walkway - sheltered from the elements, so to speak.  The building also features names of famous contributors to the field of chemistry, and a couple are shown in the third pic. 

Using Egg Dyes to Color Shells

We had some leftover dye solutions from coloring Easter eggs, so we tried soaking shells in the dyes - after all, they both have calcium carbonate.  A shell fossil (upper right) also dyed successfully.  The red dye seemed to work the best.

Closest Packing of Spheres

Spheres of equal size, from atoms to macroscale objects, will pack into patterns where each sphere is surrounded by six neighboring spheres in the same plane (12 neighbors in three-dimensions).  Here are gumballs in a machine and tiny polystyrene spheres that show the closest-packed pattern.

Colored Eggs and Ion Colors

Some colors associated with compounds of various transition metal ions, as depicted by colors of plastic Easter eggs.

Acid Rain Damage at the Field Museum in Chicago

Acid rain has damaged the marble (calcium carbonate) caryatid (sculpted female figure serving as a pillar) on the right more than the one on the left. If I recall correctly, these are on the south side of the museum.

Carbide lamp

For over a century, calcium carbide has been reacted with water to produce calcium hydoxide and acetylene, a flammable gas that can burn with a bright flame.  Lamps, such as those used in mines, have used these reactions to produce illumination, see: http://en.wikipedia.org/wiki/Carbide_lamp.  Acetylene produced from calcium carbide has been used in chemistry demonstrations, such as those demonstrating explosive ranges. Acetylene can burn quietly at high concentrations relative to oxygen, but can explode at low concentrations relative to oxygen.  Because exposions can occur, I will not discuss these demonstrations in more depth.    

Gas Laws on a Microwaved Container

This common occurence is a a good illustration of gas laws.  A container is heated, e.g. in a microwave, while it is open to the atmosphere.  When the container contains hot gas in pressure balance with the outside atmosphere, the container is closed.  As the gas in the container cools, its internal pressure decreases according to Gay-Lussac's law, which states that the pressure exerted on a container's sides by an ideal gas is proportional to the absolute temperature.  The net result is often that the container (like the butter tub in the picture) is deformed by the pressure of the outside atmosphere.

The Ether Monument

In Boston, the Ether Monument, located in the Public Garden, commemorates the use of ether as an anesthetic.  See: http://en.wikipedia.org/wiki/Ether_Monument.  The plaques from the monument are shown below.

LEGO Book Update

I have updated the online book "Exploring the Nanoworld with LEGO Bricks" and have posted it online at: http://mrsec.wisc.edu/Edetc/LEGO/index.html.  New sections include scanning electron microscopy and dialysis.  In the dialysis demonstration pictured, small bricks can be shaken through channels in the divider, but not the larger bricks.