High School Mathematics-Physics SMILE Meeting 1997-2006 Academic Years Phase Transitions

15 September 1998: Fred Schaal [Lane Tech HS]
He continued to discuss the question: "Why does soda at colder temperature foam less than warm soda?" Karlene Kurth [also at Lane Tech HS] indicated that the lower temperature a greater amount of CO2 to be dissolved than at higher temperature. [Also with more thermal energy the molecules were more active]. A comment was made about ICE rinks before the Zamboni [http://www.zamboni.com/] machine...Clearing snow and spreading water caused uneven ice, but hot water resulted in smoother ice.

12 October 1999: Earnest Garrison [Jones Commercial HS; Mail Run 38]
Traditional calorimeters are both expensive and unreliable, and he tried the "SMILE approach" when he found that his new school didn't have any. So, he took a little coffee cup [styrofoam], inserted it into a glass beaker [a big styrofoam cup might have been better]. A styrofoam plate served as a top, with a small hole punched through it to insert the Celsius thermometer. He measured the temperature of simmering water as 102 C, and added water at room temperature. The calculated final temperature was 26.98 C [approximately], and measured at 26 C. The crude, home-made device works better than the gleaming store-bought apparatus!

01 February 2000: Larry Alofs (Kenwood HS)
wrote on the board: Reasons why water doesn't boil ...and he asked us for answers. Some answers were:

• Not hot enough (too little molecular kinetic energy);
• Too much pressure.
Then a question was asked, "What's the difference in evaporation and boiling?" On the board, Larry sketched water molecules, showing their polar nature and the subsequent attraction between them. What does it take to break the attraction and produce evaporation?...boiling?

Larry took an Erlenmeyer vacuum flask and filled it half with water. A one-hole stopper with thermometer was placed in the top opening so the thermometer dipped into the water. He hooked up an aspirator to the water faucet and demonstrated that a vacuum resulted with the water running. With the water off, he connected the aspirator to the tube at the top end of the flask, and read the temperature of the water as 45o C. He then turned on the water, the aspirator reduced the pressure in the flask, and before long, the water inside was vigorously boiling! "Where are the bubbles forming?" asked Larry. Observation showed they formed near the surface of the water, rather than at the bottom as when placed on a hot plate. After a few minutes of discussion, Larry disconnected the flask from the vacuum, and observed that the water temperature was now 38.5o C. How come? Discussion concluded that the water molecules with the greatest energy were boiled off, leaving behind those with lower energy, and therefore lower temperature - temperature being a measure of their average energy. Beautiful, Larry!

01 February 2000: Arlyn Van Ek (Illiana Christian)
sketched a bell jar setup to evaporate water from a watch glass under vacuum (with conc. sulfuric acid to absorb evaporated water molecules). This would result in lowering water temperature and pressure to and past the triple point, where all three states of water (solid ice, liquid water, and gaseous water vapor) are in thermal equilibrium.

He drew the P-T phase diagram on the board and identified the triple point temperature as 0.01o C.

This led Earl Zwicker to show us a triple point cell which is used to obtain the triple point temperature of 0.01o C as a calibration point for very accurate thermometry. [See http://www.hartscientific.com/publications/why-tpw.htm.] My, how one thing leads to another!

27 March 2001 Don Kanner (Lane Tech HS, Physics)
drew the following temperature versus time graph for a fixed volume of water, held at atmospheric pressure, with a constant power into a system:

He remarked that his students were able to compute the relative times for the stages A, B, C, D, and E, but that they were totally unable to design an experiment to gather data.  When asked to sketch an appropriate system of  apparatus, students would typically show a block of ice with an energy source acting upon it, but not one student included a thermometer, or showed a vessel for containing water.  During stages C, D and E, when water vapor is produced, one would need something like a "weighted piston" to maintain constant pressure, while permitting the volume to expand significantly---perhaps by a factor of 1000.  His experiences illustrate the need to include experiments on thermal physics in the standard high school physics curriculum.

06 May 2003: Ben Butler [Laura Ward Elementary School]        Dry Ice
Ben
brought a supply of dry ice [the solid form of Carbon Dioxide -- C02], which he had obtained from the ice house at Harrison Street and Pulaski Road on the way to class.  He broke off a piece of the dry ice and put it into a glass of water.  The mixture boiled vigorously and produced a great deal of a cloudy vapor, just like boiling beakers in scary moviesDry ice passes from the solid phase to the gas phase at atmospheric pressure.  However, at a pressure of about  3 atmospheres, the liquid phase can also be produced.  Ben produced the liquid phase in a clear flexible tube with a valved opening at one end and attached to a pressure gauge at the other end.  He put a small piece of dry ice inside the tube, and closed the valve; then the pressure steadily increased as it vaporized.  When the pressure exceeded about 3 atmospheres, we saw small droplets of the liquid phase of C02Beautiful!  The apparatus was obtained from Flinn Scientifichttp://www.flinnsci.com/.

What an elegant experiment to show the three states of CO2! Now, Why does dry ice feel dry?  Very slick, Ben!

21 October 2003: Carl Martikean [Crete-Monee HS, physics]     Enjoyable Experiments with Dry Ice
Carl brought in a bag containing about 5 kg of dry ice, which he had obtained at Praxair [http://www.praxair.com/] the previous day, and had used in his physics classes today.  We then proceeded to do a fascinating series of experiments using dry ice:  [He obtained these experiments from the publication 39 Dazzling Experiments with Dry Ice by Fizzbang Science: http://www.amazon.com/39-Dazzling-Experiments-Dry-Ice/dp/0971848033/ref=sr_1_2?s=books&ie=UTF8&qid=1313678711&sr=1-2.]

• The Squealing Coin: Sound Effects with Dry Ice.
• Making a Fountain of Soap Suds -- just put some dry ice inside a pop bottle containing some dishwashing soap, and watch what happens.
• Heavy Balloon-- put dry ice in a plastic pop bottle, add a little water, and put a balloon over the mouth of the bottle.  The balloon fills with CO2 gas.  That balloon definitely falls more quickly than one that he blew up to the same size.  How come? What about poor Galileo and the Leaning Tower of Pisa?  For more information on Galileo and his famous GedankenExperiment  --- which actually may not have been done, see http://plato.stanford.edu/entries/thought-experiment/ and http://www.sciencenews.org/sn_arc99/12_18_99b/fob7.htm. Also, see the review of the book Galileo's Daughter by Dava Sobel, who claims that Galileo actually did drop balls (with mixed results) from the leaning tower of Pisa:  http://www.crimsonbird.com/history/galileos-daughter.htm
• Rubber Band Snake -- wrap a rubber band around a piece of dry ice.  It becomes thoroughly cold, and loses its elasticity.  When the rubber band is removed from the dry ice and placed on a table, it seems to come to life and wriggle around.  Like a snake!
• Frozen Banana Hammer --  It works!
Safety Precautions:  Use dry ice only with adult supervision.  Never touch dry ice with your bare skin -- it may cause frostbite!  Use dry ice only outdoors or in a well-ventilated room to prevent buildup of carbon dioxide gas.  Do not inhale vapors -- inhalation of vapors may cause suffocation, since carbon dioxide displaces oxygen.

Carl plunged a lit match into his plastic bag containing dry ice, and the flame went out quickly.  Carl also described using a mixture (Caution:  Fire Hazard!) of Dry Ice and Acetone (which remains a liquid) to freeze flower petals. Bill Blunk mentioned that magnesium metal will continue to burn in the C02 atmosphere around dry ice, and that carbon soot is produced in the reaction.  Bill also suggested that, by placing a hot dog in one finger of a rubber glove, dipping the glove into liquid nitrogen, and then cutting off the finger with a butcher knife, you could create a nice, macabre Hallowe'en demonstration.  Good idea, but be sure not to cut off the wrong finger, Bill!

Nicely phenomenological, Carl!

28 September 2004: Charlotte Wood-Harrington [Gwendolyn Brooks HS, Physics]           The Physics of Guinness Stout (Let's Party!)
Charlotte felt that it was more direct to ask for forgiveness (afterward) than to seek permission (before), in presenting a lesson on the behavior of bubbles in a properly poured glass of the scintillating Irish brew mentioned above.  She told us that the small bubbles near the outside edge of the glass actually fall, whereas the larger bubbles near the center of the glass rise.  For purely scientific purposes, she demonstrated the effect by slowly pouring the beverage into the side of a glass.  We saw the bubbles on the outside fall!  But, how come?  Charlotte claimed that the essential item was a  small widget that had been strategically placed inside the can by the manufacturer. She tore the can apart and showed us the widget -- a ball about 1 inch (2 cm) in diameter filled with Nitrogen gas.  See the website:  How Does a Widget in a Beer Can Work? http://home.howstuffworks.com/question446.htm. Charlotte showed us that an Alka-Seltzer® tablet placed into a glass of water would produce the same effect. For more details also see Do bubbles in Guinness go down?  http://www.stanford.edu/group/Zarelab/guinness/why.html.

Charlotte recommended that we should consider celebrating day number 10,000 or 20,000 on this earth. She ran an EXCEL® program that would calculate the number of days since the specified date of birth.  For example, a random person born on 23 May 1926 has been on this earth for 28,618 days.  In a few years, that person could celebrate day number 30,000What a great idea for a party!

Finally, Charlotte informed us that Chicken McNuggets® may be ordered at McDonalds™ Restaurants in quantities of 6, 9, and 20 per package.  What is the largest number of Chicken McNuggets that is impossible to order at McDonaldsHint:  apply ternary logic, but observe that the answer is not "42", since 6 ´ 7 = 42 --- apologies to A Hitchhiker's Guide to the Galaxy by Douglas Adams [See http://en.wikipedia.org/wiki/The_Hitchhiker's_Guide_to_the_Galaxy].

Thanks for the ideas, Charlotte!

25 January 2005: Don Kanner [Lane Tech HS, physics]          Three No-Trumps
Don made a presentation on candles, based upon a Mr Wizard program featuring Don Herbert.  Don lit a candle, and asked us what was burning, and where it was hottest.  We discussed the issue for a moment.   Don placed a horizontally-held sheet of metal gauze intersecting about half way up the vertical height of  the flame. When we looked down at the flame from above, there was no flame above the gauze, and the the flame below was hollow; with only its outside burning!  The candle wax must melt and then vaporize, and it is the vapor that actually burns, by chemical reaction with oxygen in the air. Roy Coleman suggested that he hold an unburned wooden match stick into the flame, to show that the stick begins to burn only at the edges, at first. Don was able to re-light the candle above the gauze sheet with a match.  Don then put a glass chimney down and centered around a burning candle.  He then sprayed smoke across the top of the chimney.  Amazing -- the smoke flowed down the inside surface of the chimney to the flame, and rose above the flame through the center of the chimney, and out. [Don  Herbert, Don Ivey, and Don Kanner constitute the three no-trumps.]

Fascinating, Don!

22 February 2005: Fred Farnell & Don Kanner [Lane Tech HS, physics]              Fizzing Pop Bottles
Fred and Don
investigated this burning scientific and societal question: How and why do soft drinks -- which are often called "pop" in Wisconsin, "cold drinks" or just "coke" down South, "soda" in New England, and "cola" or "limonade" in Europe -- lose their FIZZ.  They put this question to direct experimental test, brought out several plastic bottles (about a half-liter in capacity) of Coca Cola™ and Dr Pepper™.  These recently purchased bottles seemed to be about the same temperature and internal pressure, since they felt "similar" when we squeezed them.  First we investigated the effects of (1) shaking the bottles a vigorously, and then allowing their contents to settle for a few seconds (until the foam disappears), as well as (2) opening the plastic caps slowly or quickly.  Here is a recording of some of our results:

 Opening Speed? - \ - Shaken? Slowly Quickly Not Shaken Slight hissing; a little bubbling More Foam Shaken Vigorously Slight hissing; Lots of foam Bottle #1: lots of foam Bottle #2: very little foam
Evidently, shaking the bottle tends to produce a more violent opening, as does opening the cap quickly.

Just what causes the violent foaming? Through class discussion, we identified the following points as likely to be relevant..

• Most of the carbon dioxide (CO2) is dissolved in the liquid as an ionic solution of carbonic acid (H2C03), and only a small amount is present as C02 gas.
• When the bottle is opened (slowly or quickly), the gas pressure inside the bottle also decreases (slowly or quickly).
• When the bottle is shaken vigorously, some of the CO2 dissolved in the liquid becomes gaseous before the bottle is opened. The foaming is a manifestation of this conversion to the gaseous state. However, even after the foaming disappears, a significant amount of gaseous C02 may remain. In fact, it may take an hour or so for that CO2 gas to re-dissolve in the liquid.
• Curiously, bottles that look the same  (bottle #1 and bottle #2 in the table) may respond differently to vigorous shaking. The amount of  CO2 gas in the shaken bottle depends upon the precise details of the shaking process. The shaking process is a means to induce phase rearrangement that returns to equilibrium quite slowly, in practice.  It is quirky, in effect!
Don Kanner illustrated the phase rearrangement induced by shaking by drinking about half of the contents of one of the Coke bottles, re-tightening the cap, and shaking it vigorously.  When -- just as before -- the bottle was opened a little afterward, there was  foam all over the place! When he repeated the process of tightening the cap, shaking the bottle, and opening it several times, the amount of foaming decreased each time.  Finally, Don then tasted the contents --- flat Coke! He had removed most of the carbonation through this process. Several groups in the audience performed the same experiments, drinking some of the contents with small cups that Don had provided, with the same conclusions.  For a related discussion, see the discussion of metal cans of Guiness™ Stout  by Charlotte Wood-Harrington at the SMILE meeting of 28 September 2004:   mp092804.html.
• Q: What is the meaning of the numbers 10 -- 2   -- 4 on the traditional logo for Dr Pepper™?
• A: One possible interpretation is the following: At 10 am you drink it; at 2 pm you become ill, and at 4 pm you die.
Sweet science with sweet stuff!  Thanks, Fred and Don!

12 April 2005: Dianna Uchida [Morgan Park HS]              Elephants and Flowers
Dianna
showed us a plastic sheath that seemed quite rigid.  She filled it with warm water (about 50 °C), and showed us that it became much more flexible.  She then showed us the Wonder Vase, which was initially a flat plastic sheath.  She added warm water to it, and it became quite flexible, so that she could mold it into the form of a roughly cylindrical vase.  When she poured the hot water out of it, it retained that new shape.  She then added cold water to it, and put flowers into it, illustrating its use as a vase.  Then she removed the flowers and water, and again filled it with warm water.  The material became quite flexible, so that she could mold it into a flat sheet again.  Remarkable, NON?  Larry Alofs mentioned that an old term for plastic was "thermoplastic", because of its property of becoming more flexible when warm.

Q: How do you make an elephant fly?