Chemical Education Today
Reports from Other Journals
The Best of Chem 13 News by Kathy Thorsen
This column is designed to give JCE readers highlights from Chem 13 News, a monthly publication from the University of Waterloo (Ontario, Canada) for chemistry educators. I have selected a variety of articles appearing from January through May 1998 that captured my interest as a chemistry teacher. I would like to share them with others. The following paragraphs provide references to innovative ways of introducing students to general chemistry concepts and engaging them in experimental design. Through these methods they begin to develop a better understanding of concepts discussed in class. Converting “Recipe” Experiments into Scientific Experiences As a high school chemistry teacher, I’ve seen (all too often) students beginning a laboratory investigation without a clue about how or why the activity should be done. Even if students read the instructions and answer the prelab questions, they struggle to complete the mechanics of the activity and fail to make connections to the concurrently studied unit. Unfortunately, the scientific thought process is either lost or never occurs during the investigation. In the January 1998 issue (p 8), Alberto Moniz introduces an intriguing journal writing technique for high school laboratory investigations. A format is described in which students express preconceptions and then decide what and how those observations will be expressed before beginning the investigation. After the activity, students discuss their results in small groups, followed by a class discussion to identify and explain any discrepancies. The use of this journal writing procedure motivates students to think critically about misconceptions and experimental conclusions that relate to the scientific concepts discussed in class. Not only does the author include a description of each log section and a copy of the student handout, but he also applies the technique to a specific lab, “Constructing the Periodic Trends” in the February 1998 issue (p 12). I have incorporated this writing strategy in my first year accelerated (honors) chemistry course. Using the science log format, my students responded positively and asked fewer questions while completing the laboratory investigation. After reading their first entry, I gave my students a sample entry for this activity to clarify my expectations. An “Egg-citing” Activity Open-ended laboratory investigations stimulate students to think as scientists. As mentioned previously, many students only get experience following “recipe” activities rather than designing their own investigation. Linda Ford presents an activity in the January 1998 issue (p 6) that introduces students to the scientific process using an egg. The goal is to confirm or disprove the statement: “The density of a whole 1368
chicken egg is equal to the arithmetic mean of its parts—the yolk, the white, and the shell.” The students are responsible for determining their methodology, choosing an egg, and making all the measurements within the class period. The author describes procedures used by her students and previous results. This activity demonstrates to students “that an experiment can produce only an estimate for the true state of nature”. An integral aspect of the investigation is the student’s freedom to discuss concerns and methods in order to minimize the uncertainty of their results. Microscale Chemistry Can Be a Gas Several past issues outline experiments that can be done with gas-filled syringes (using CO2, H2, O2, etc). The article “Microscale Gas Chemistry, Part II: Experiments with Hydrogen Chloride”, found in the April 1998 issue (p 10), outlines a method for generating hydrogen chloride gas and is one of eight related experiments. This particular procedure uses a thermal method suitable for classroom demonstrations or for students with advanced laboratory skills. The reaction uses sodium hydrogen sulfate monohydrate, NaHSO4·H2O and sodium chloride, NaCl. Upon heating the mixture, hydrogen chloride gas is collected in a 60-mL syringe. The yield and purity, which depend on the reaction vessel size, is outlined in a table. In addition a diagram of the reaction apparatus, procedure, and disposal methods are outlined in detail. The experiments using the hydrogen chloride-filled syringes cover a myriad of topics such as pH, acid–base neutralization, density, equilibrium, gas laws, and Graham’s law of diffusion. Each procedure includes helpful hints, diagrams, and a brief explanation of the concept involved. A Solution for Teaching Molarity No matter how molarity is introduced, mastery of the topic requires many practice calculations. Glen Loveridge offers a hands-on activity that incorporates the mathematical practice. This activity in the May 1998 issue (p 23) requires students to make solutions of lead(II) nitrate, Pb(NO3)2, and sodium iodide, NaI. After mixing the solutions, students record the volume of the precipitate and calculate the number of moles of each reactant. Student worksheets and directions are included in the article. In addition to the author’s procedure, I would ask students to filter, dry, and weigh the precipitate to calculate the number of moles of lead(II) iodide. Conservation of Mass in a Soda Bottle Students are often misled by the “disappearance” of solid or liquid reactants and do not consider the production of gases, a common and invisible product of many chemical reactions. Thus, Charles Malerich and Patricia K. Ruff have
Journal of Chemical Education • Vol. 75 No. 11 November 1998 • JChemEd.chem.wisc.edu
Chemical Education Today
devised a demonstration to prove the conservation of mass with a variety of possible gas-generating reactions. The setup outlined in the May 1998 issue (p 26) is cost-efficient, safe, and easy to assemble. The liquid reactant is poured into a 1or 2-L soda bottle with the solid (packaged in tissue) suspended from a paper clip hook attached to the bottle cap. The bottle is then inverted so that the entire reaction takes place in a closed system. With this method, the mass of the system can be measured before and after the reaction. The authors explain in detail the safety concerns and a test of the durability of capped soda bottles where gas pressure is increased. Tantalizing Tidbits for Teaching Chemistry
Typecasting a Reaction Analogies and metaphors can be used to relate abstract concepts to students’ experiences (as long as students remember the science as well as the analogy). The February 1998 issue (p 3) presents a catchy metaphor that relates the ionic exchange of a double replacement reaction to the frenzy of losing one’s date during a fairy tale ball.
Puzzling Calculations An interesting crossword puzzle of numbers can be found in the April 1998 issue (p 9). This puzzle disguises the practice of simple calculations such as stoichiometry, mass-molevolume conversion, molar mass, and more. The answers can be found on page 13 of the same issue. NSTA: Making a Mark on the Internet Map The Internet is becoming a significant resource for teachers of all ages and disciplines. Chem 13 News, like many publications, has a column featuring the up and coming Web sites—Chemistry on the Internet: Untangling the Web. In this year’s January and February issues, the Web site of the National Science Teachers Association is explored. The column outlines and evaluates several valuable links to the NSTA home page. If you have not yet jumped on the Internet train, be sure to check out this column and the NSTA Web site (http://www.nsta.org). Kathy Thorsen teaches at Menomonee Falls High School, N84 W16579 Menomonee Ave., Menomonee Falls, WI 53051;
[email protected].
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