edited by DOUGLAS D . SMITH Guilford High School
Chemical of the Day Thomas O'Brien
of fourteen groups according to its electronegativity and painting each square the appropriate color. Fourteen shades of blue were ~ r e ~ a r hv e dmixine dark blue latex paint with white. Francium and ceHium were painted the lightest blue while fluorine was ~ a i n t e dmidnieht blue. The midnight blue was prepared by iixing dark blue paint with a smallimount of carbon. The Noble aases were minted dark brown since they have no e~ectronegativit~ b l u e s . Commercial and handmade stencils were used in painting the atomic numbers and atomic masses on each sq;are. Aprotective spray was a n ~ l i e dover the entire chart. Following Bean's suggestion, the students mounted a framed picture and explanation on the wall. Such a chart is inexpensive to produce but does require dedication on the part of the students. The project added color to the classroom wall, vividly showed the trends in the electronegativity, and, perhaps most important, provided a way for students to leave their mark on the school. ~~
St. Henry High School 3813 Dixie Hwy. Erlanger. KY 41018
I n recent years the emergence of the AgC1-is-a-paleereen-eas svndrome has heralded the need for teachina more zescri&vechemistry. One way that this can be accomilished is to devote a few minutes of each post-lab discussion to focus on the key physical and chemical properties, sources, and industrial uses of one of the chemicals used in that particular lab. If students' handouts are prepared for each lab, the students will discover that many chemicals (i.e., a t least half of the top 50 industrial chemicals are used in a t least one high school lab) which seemed to be esoteric substances of the laboratory are in fact crucial to our economy and lifestyle. Descriptive chemistry can thus he presented in a relevant and "timeless" way. References that are of particular value for preparing the "Chemical of the Day" handouts are
~
A
' Bean, W. K..
The Science Teacher, 47, (October 1980).
50 chemicals and chemical manufacturers.
2) "Chemical and Engineering News: Key Chemicals and Polymers," 3rd edition-reprints of C & ENews chemical information pages on 45 different industrial chemicals collected in one volume. 3) Chemical of the Month-a feature of T H I S JOURNAL.
4) Real Wodd of Industrial Chemistry-a feature of T H I S JOURNAL. To date two of the articles would be especially useful: "HzSOa4n Acid Can Be Basic" (August 1979) and "Use of Oxygen in the Treatment of Sewage" (Fehruary 1980). 5) "Lifestyle," "Chemicalstyle"-two booklets of essays prepared hy the Chemical Manufacturing Association (1825Connecticut Ave., N.W., Washington, D.C. 20009) whose purpose is to show the vital role that the chemical industry plays in our lives. The following chemicals are focused on: Volume I-HzSOn, NH3C12,NaOH, and HCI; Volume 11-HNOB, NazCOs, P, phosphates and phosphoric acid, H2 (fuel from water), formaldehyde, urea, benzene, and Cr and its compounds. (Note: CMA gives unrestricted reprinting permission for these articles.) 6) "The Merck Index: An Encyclopedia of Chemicals and Drugs," 9th Ed. 7) Encyclopedias.
A Colorful Periodic Table Paul Hobe Hoover High School 605 South Fair Oaks North Canton. OH 44720
Painting a periodic table on a classroom wall can be an instructive, colorful, and useful project. Using some of the techniques mentioned by William K. Bean,' three students painted a version of his chart. It was decided that a chart showing electronegativity variations would help students differentiate between metallic and nonmetallic elements as well as aiding them in determining ionic character in bond types. T h e students started the project by washing the wall and then painting the entire wall a beige background color. Eight-inch squares were masked off to form the spaces needed for the chart. It was decided to show the trends of the elements' electronegativities by classifying each element into one
Notes from Physics Journals A Safe Pyrex" "Vanishing Solution"
Donald Day's article1 points out the easy availability of nonvolatile, nontoxic organic compounds that may he used to prepare solutions that have indexes of refraction matching Pyrexm glass. In the past, preparations have included volatile, toxic, and carcinogenic compounds. He recommends the listed compounds from Cargille.2 Code Code Code
S 10
50 40
Silicone oil Mineral ail Mineral oil
n = 1.399 n = 1.458 n = 1.570
$17.00/16oz. $11.00/16oz. $21.00/16oz.
A further hint was to shine a low power laser beam through the solution and the immersed Pyrex" object to see if any deviations occurred.
' Day, Donald A,, The Physics Teacher 15,7 (1977).
Cargille Laboratories, Inc., 55 Commerce Road, Cedar Grove, NJ 07009. Reverse Cartesion Diver "Trick"
We are aware of the use of Cartesion divers to talk about how pressure changes the volume of a gas and, in this case, also increases density. William A. Butler1 has added the suggestion that by using a rectangular-based glass bottle with flat sides, the process may be reversed. Adjust the pressure so the diver is keut a t the bottom, and then press on the narrow sides of the hottle. The diver can he made to rise. Editor's note. It is possible to do this demo by using a clear plastic bottle, for instance the container for dishwashing detergent. Less hand pressure is needed to change the volume.
' Butler, William A,, American Journaiof Physics, 49, 1 (1981) Volume 59
Number 3
March 1982
243
