Communication pubs.acs.org/jchemeduc
How Heavy Are You? Find the Answer in the Periodic Table Klaus Woelk* Department of Chemistry, Missouri University of Science & Technology, 400 West 11th Street, Rolla, Missouri 65409-0010, United States
Downloaded by UNIV OF PENNSYLVANIA on September 5, 2015 | http://pubs.acs.org Publication Date (Web): September 4, 2015 | doi: 10.1021/acs.jchemed.5b00172
S Supporting Information *
ABSTRACT: In a classroom or take-home activity, students are challenged to write their name as a combination of chemical-element symbols and calculate “their” molar mass. Age-appropriate versions ranging from middle school to entry-level college classes are discussed. Acceptable molar-mass suggestions may be used in a competition for the heaviest combination or weighed against a preset value derived from the teacher’s name. The activity is suited for exploring information provided with the periodic table at times when atomic and molar masses are first introduced.
KEYWORDS: Elementary/Middle School Science, High School/Introductory Chemistry, First-Year Undergraduate/General, Public Understanding/Outreach, Humor/Puzzles/Games, Nonmajor Courses
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Age-Appropriate Variations
hemical stoichiometry is the basis for calculating amounts, yields, or masses of reactants and products, concentrations of solutions, and volumes or pressures of gaseous compounds. Almost all quantitative information about chemical reactions is derived from stoichiometric calculations using the average atomic masses found in the periodic table of the elements. Nonetheless, entry-level chemistry students often seem to view the unit conversions from grams to moles and moles to grams as unnecessary and complicated. The first step in finding the conversion factors (i.e., the average molar masses) is the addition of atomic masses in their stoichiometric ratios. For middle and high school students but also in introductory college chemistry, I have used an activity challenging students to find a virtual molar mass directly or closely related to their name or personality.
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For 6th to 8th grade classes, students should be allowed to skip letters in their name that “don’t work.” Hence, Christina would be able to use carbon (C), hydrogen (H), iodine(I), sulfur (S), titanium (Ti), and sodium (Na) but skip the letter “r” in her name for which no equivalent can be found in the periodic table. In high school or college competitions, it might be more appropriate to challenge the students trying to find other names or functions associated with their personality. For example, a student named Steven used Es (einsteinium), Te (tellurium), Ba (barium), and N (nitrogen) explaining that Esteban is his name in the Spanish language. Challenge against a Minimum Threshold
I often use my first name and its “molar mass” as a challenge to compete against. My combination of letters, K (potassium, 39.10 g/mol), La (lanthanum, 138.91 g/mol), U (uranium, 238.03 g/mol), and S (sulfur, 32.07 g/mol), contains the heavy atoms lanthanum and uranium, and the threshold, albeit the short name, is reasonably high (448.11 g/mol). Students will try to surpass “my mass”, which may become a competition rewarded with applause (or a small prize). If one likes to conduct this activity in a similar way but their name cannot be “written in chemistry” or results in a molar mass too small (or too large) for a reasonable challenge, I suggest to use the name “teacher” as a substitute. The threshold will then be 522.67 g/ mol as composed of Te (tellurium, 127.60 g/mol), Ac (actinium, 227 g/mol), H (hydrogen, 1.008 g/mol), and Er (erbium, 167.26 g/mol).
ACTIVITY
Basic Idea
Similar to the activities described in “Write Your Name in Chemistry”,1 or designing T-shirts2 students are asked to find a combination of elements symbols which, put together in the right order, resembles their first, middle, or last name. What is not suggested in these activities is the added instructional benefit when students are asked to calculate a molar mass for their combination of symbols. For example, Ben would use Be (beryllium, 9.012 g/mol) and N (nitrogen, 14.01 g/mol) to represent his name, while Kathryn could use her nick name Kathy as formed by the combination of K (potassium, 39.10 g/ mol), At (astatine, 210 g/mol), H (hydrogen, 1.008 g/mol), and Y (yttrium, 88.91 g/mol). Accordingly, Ben’s “molar mass” would be 23.02 g/mol and Kathryn’s 339 g/mol. © XXXX American Chemical Society and Division of Chemical Education, Inc.
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DOI: 10.1021/acs.jchemed.5b00172 J. Chem. Educ. XXXX, XXX, XXX−XXX
Journal of Chemical Education
Downloaded by UNIV OF PENNSYLVANIA on September 5, 2015 | http://pubs.acs.org Publication Date (Web): September 4, 2015 | doi: 10.1021/acs.jchemed.5b00172
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CONCLUDING REMARKS This entertaining activity is aimed at reducing anxieties students may experience when confronted with the chemical elements and their symbols for the first time. Because element symbols are combinations of letters that, to the novice, might seem arbitrary or counterintuitive (e.g.: the symbol for potassium is K, not P or Po), teachers could spend much time explaining the origin of each name and symbol.3 Instead, students are encouraged to browse the periodic table on their own and become familiar with names and symbols in a playful way. In this regard, the activity’s pedagogy is similar to those published earlier,1,2,4,5 but it utilizes in addition the concept of atomic mass. It might still be useful to point out to students that the combinations given, and those that they will come up with, are not actual compounds or indicative of how elements actually combine. When a name can be written in more than one combination of chemical elements, I encourage students to find the largest “molar mass” possible. For example, Nicholas could simply use Ni (nickel, 58.69 g/mol), C (carbon, 12.01 g/mol), and K (potassium, 39.10 g/mol) to represent his nickname (109.80 g/ mol), but it is quite obvious that the full name has more potential. A heavier combination is Ni (nickel, 58.69 g/mol), C (carbon, 12.01 g/mol), H (hydrogen, 1.008 g/mol), O (oxygen, 16.00 g/mol), La (lanthanum, 138.91 g/mol), and S (sulfur, 32.07 g/mol) leading to 258.69 g/mol, but it is N (nitrogen, 14.00 g/mol), I (iodine, 126.90 g/mol), C (carbon, 12.01 g/ mol), Ho (holmium, 164.93 g/mol), La (lanthanum, 138.91 g/ mol), and S (sulfur, 32.07 g/mol) providing the highest value (488.82 g/mol). This activity may also be used to discuss significant figures. While five significant digits can be used for the name Nicholas (488.82 g/mol, see above) because all average elemental masses in this entry are known to within 0.01 g/mol or better, Amy, using Am (americium, 243 g/mol) and Y (yttrium, 88.91 g/ mol), can reasonably only provide 332 g/mol reflecting the limited precision to which americium is known. If no time can be spent in class, this activity may be used as take-home challenge with solutions e-mailed to the teacher by a preset deadline. Timely entries should be prescreened and valid solutions sorted in order of increasing molar mass. Students should always provide a molar-mass calculation of their combination together with the element names and symbols. In addition, they should provide an explanation if a name or entry cannot easily be recognized as theirs. The request for explanation has led to creative and funny descriptions (see Supporting Information) revealing how much some students have engaged in the activity.
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Communication
REFERENCES
(1) Eichstadt, K. A Large Lecture Hall Activity-Writing Your Name ″in Chemistry″. J. Chem. Educ. 1993, 70, 37. (2) Palmer, J.; Brosnick, L. Designing Element T-shirts: Spelling with the Periodic Table. J. Chem. Educ. 2005, 82, 517. (3) See for example: WebElements, http://www.webelements.com/ (accessed Aug 2015). (4) Woelk, K. Matching Element Symbols with State Abbreviations: A Fun Activity for Browsing the Periodic Table of Chemical Elements. J. Chem. Educ. 2009, 86, 1205−1207. (5) Kavak, N. ChemPoker. J. Chem. Educ. 2012, 89, 522−523.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available on the ACS Publications website at DOI: 10.1021/acs.jchemed.5b00172.
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Examples of most creative submissions (PDF, DOC)
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest. B
DOI: 10.1021/acs.jchemed.5b00172 J. Chem. Educ. XXXX, XXX, XXX−XXX
