Carl Martikean [Crete-Monee HS, physics]
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://sciencekit.com/fizzbang-science---39-dazzling-experiments-with-dry-ice-book/p/IG0029038/]
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!
"F" Lee Slick [Morgan Park HS,
physics] More on Matches and
burning stone = sulfur]
Motivated by the Paper Match Rocket presentation by Bill Blunk at the last meeting [mp100703.html], Lee held a contest in his science class to see which team could shoot a rocket over the greatest distance. The girls team won, because they followed the directions more carefully! Lee also raised the question of the chemical reactions involved in burning sulfur in matches. The usual reaction is given as S + O2 ® SO2, which is misleading in several respects. First, burning sulfur in air results in a mixture of SO2 and SO3, depending on the temperature and the amount of oxygen present. In a match, the production of SO3 dominates that of SO2, because of the lower temperature and oxygen-enriched environment. Second, the sulfur is usually present in the poly-atomic form S8. Thus, a more correct chemical reaction would be S8 + 12 O2 ® 8 SO3. Put that in your pipe and smoke it -- making sure to use non-toxic matches in lighting your pipe! Good work, Lee!
For additional information see the websites Sulphur and its Compounds: http://en.wikipedia.org/wiki/Sulfur and The History of Matches: http://inventors.about.com/library/inventors/blmatch.htm.
Jane Shields [Calumet HS,
Jane made a "blow by blow" description of her attempts to construct a Weather Frog, which hops up a ladder during periods of high atmospheric pressure and down the ladder at low atmospheric pressure. The idea is to place a flexible plastic seal over the top of a quart [liter] glass jar, with a string wrapped around a (sewing needle) shaft a few times. One end of the string is attached to the underside of the plastic seal, and a small weight is suspended from the other end. The shaft is free to rotate. One end of a rigid metal wire is attached perpendicularly to the shaft, and the paper frog is hooked to its other end. As air pressure changes, the seal moves slightly up or down, so the shaft rotates, and the frog moves up or down. Jane's apparatus almost worked, and she was determined to succeed with it. Very good, Jane!
A nice description of the principles behind the operation of the Weather Frog, as well as details for its construction, are contained on the Nebraska Earth Systems Education website pages Too Heavy For Me; An Elementary Unit about Air Pressure from which the following has been excerpted:
HOW A BAROMETER WORKS: "A barometer has a piece of special metal in it called corrugated metal that squeezes down when heavier air pushes on it and expands up when lighter air does not push so much on it. There is a needle attached to the metal that points to a number on the dial to tell the air pressure. There are also words on the barometer to tell what the weather conditions will do according to the air pressure: rain, change, and fair. Lower numbers indicate low pressure and higher numbers indicate high pressure. Air pressures usually range from 29.00 to 31.00 inches [of mercury] in Nebraska."Jane also passed around an RD Challenge --- illusions that appeared in the September 2003 issue of The Readers Digest [http://www.rd.com]. Other illusions appeared in the January 2002 issue. This website also contains links to the Counter-rotating Spirals Illusion [http://dogfeathers.com/java/spirals.html], Grand Illusions [http://www.grand-illusions.com], and Artful Illusions [ http://members.aol.com/Ryanbut/illusion1.html]. Neato!
Bill Blunk [Joliet Central HS,
Columbus and the Telescope
In his unofficial capacity as guardian of public interest in historically accurate portrayal of science in the media, Bill was somewhat surprised to see an advertisement [from a furniture store] portraying Christopher Columbus looking out from his sailing vessel with a telescope. This image was quite remarkable, since Columbus sailed in 1492, and the telescope was invented around 1608. For more information on CC, the son of a wool merchant who found his way to the new world, see The Columbus Navigation Homepage [http://www.columbusnavigation.com]. Who really invented the telescope, and when? For insights, see http://space.about.com/cs/basics/a/spacefaq12.htm or http://www.ee.umd.edu/~taylor/optics3.htm, or perhaps even http://news.bbc.co.uk/1/hi/sci/tech/380186.stm.
It makes one wonder about the furniture, as well! Thanks for blowing the whistle on this one, Bill!
Babatunde Taiwo [Dunbar Vocational HS,
Graphics Calculator and Motion Sensor
Babatunde showed that his TI-83 graphing calculator, CBL Ranger motion sensor, and Vernier Logger Pro [http://www.vernier.com/soft/lp.html] graphical interface could be used to display graphs of idealized motion, as well as record the motion of moving objects. First he displayed a distance-time graph that looked like the one shown here, with distance marks in meters and time marks in seconds.
He set up the motion sensor and software so that it would record the position of an person walking across the room. The objective was to reproduce the graph given above with one's own motion --- by being at the right place at the right time. After three trials, Babatunde was able to reproduce the curve pretty well. Walter MacDonald then tried it with this curve, as well as the curve given below. He was able to reproduce the curves on his first attempts.
Babatunde then showed the curves of velocity and acceleration versus time, as determined numerically from the positions. He then pointed the motion sensor downwards, dropped a ball from a height of about a meter, and used the motion sensor to record its vertical position versus time. He was able to follow the ball through several bounces. Then he showed the graphs of velocity and acceleration versus time. The acceleration was negative, and of modest relative size, when the ball was in flight, whereas when the ball struck the floor it became quite large and positive. [Because of the intrinsic time resolution of the apparatus, we were seeing some time averaged acceleration of the ball, rather than its instantaneous acceleration.] These are very visual exercises in the kinematics of motion, which allow us to experience the direct connection of motion with distance-time graphs. Thank you for showing this to us, Babatunde!
For additional information see the websites: Activity Investigating Motion: http://www.math.mtu.edu/gk-12/investigatingmotion.html and Utilizing the Graphing Calculator in the Secondary Mathematics and Science Classroom: http://www.esc4.net/math/.
Babatunde also showed a spinning top toy that he had recently obtained at American Science & Surplus [ http://www.sciplus.com/category.cfm?category=13]:
Here, Kitty Kitty ... A top that’s fun! A top that doesn’t need string or practice or coordination. Twist the winder, push the button, and the colorful plastic top bounces around on its spring bottom, lights up brightly (batteries included), and spins for a very long time. A nice distraction for a jaded child or a bored tabby cat
Bill Colson [Morgan Park HS,
Molecular Expressions/ Florida State U Website
Bill passed around information from their website, http://micro.magnet.fsu.edu/, on the following topics:
Bill also passed around some geometrical questions concerning Tumbling, Spinning, and Plummeting, which appeared in the October 2003 issue of Discover Magazine in the feature article "bogglers by scott kim": http://www.discover.com/issues/oct-03/departments/bogglers/.
Fred Schaal [Lane
Tech HS, mathematics]
the Great Divide
Fred traveled extensively on the Union Pacific Main Line last summer, during which he noticed that a number of the tank cars were "sway backed". He wondered why they were built that way. During the discussion, the following points were raised:
Notes taken by Porter Johnson