Chemistry for Everyone

612 Journal of Chemical Education • Vol. 84 No. 4 April 2007 • www.JCE.DivCHED.org

Sudoku Puzzles as Chemistry Learning Tools WThomas D. Crute* and Stephanie A. MyersDepartment of Chemistry and Physics, Augusta State University, Augusta, GA 30904; *tcrute@aug.edu

The chemistry curriculum still includes some materialthat requires rote memorization, often including distinctionsbetween superficially similar items. Mastering such materialis seldom exciting and many students are reluctant to per-form these tasks. Therefore, a method that would make thesetasks more interesting is desirable. There are several examplesof puzzles being used in the classroom including wordsearch(1), letter matrix (2), and crossword (3) puzzles. We have de-veloped sudoku puzzles that use chemistry terms in such away to meet this goal.

Sudoku puzzles have become quite popular in recentyears and routinely appear in media such as newspapers,puzzle books, Web sites, or can be created through availablesoftware (4, 5). The most common puzzles use numbers onethrough nine in a 9 × 9 grid that is subdivided into 3 × 3boxes, although different sized grids and characters other thannumbers have been used. A completed puzzle has one instanceof each number or symbol per row, column, and box. A lim-ited number of symbols are strategically placed in the grid asthe “givens” for a starting point, and the puzzle solver mustuse logic to determine which symbol should appear in eachof the remaining spaces. The easiest puzzles only require simplelogic or solving by inspection, while progressively more diffi-cult puzzles require more sophisticated or multistep analysisand problem solving. A combination of ruling out symbolsfor a particular space to avoid repetition, and determiningwhich symbol is still needed in a particular row, column, orbox is a typical strategy of solving by inspection. The RoyalSociety of Chemistry has a chemistry sudoku puzzle that usessymbols instead of numbers and includes element symbols andisomers of heptane (6); however, these symbol-based puzzlesdo not have the learning element that our puzzles have intro-duced by mixing names with structures or specifically pick-ing easily confused terms as puzzle symbols.

A hallmark of solving a sudoku puzzle is the reliance oncareful attention to which symbols are already present in a givenrow, column, or box. A second feature is the repetition involvedin examining the details of the puzzle during the solving pro-cess. These characteristics prompted us to design sudokupuzzles that incorporate lists of chemistry terms that studentsneed to know, such as polyatomic ions, organic functionalgroups, or strong nucleophiles. It was believed that the repeti-tion involved in solving the puzzles would aid in memoriza-tion of these items. Furthermore, easily confused symbols thatare superficially similar but different upon closer inspection,such as sulfate and sulfite polyatomic ions, would be ideal can-didates for inclusion since students must attend to the detailsof each symbol to ensure no repetition. Mixing structures andnames within the same puzzle demands that students pay at-tention to these correlations. With these characteristics inmind, puzzles were designed that included both names andstructures so that the correlation between them must be madeby the puzzle solver. Figure 1 shows a puzzle based on func-tional groups that includes the names, complete structures,generalized structures, structural variations such as both pri-

mary and secondary amines and structural abbreviations foraldehydes and carboxylic acids that force students to recog-nize allowed variability in conveying these structures. Two ad-ditional puzzles—one based on polyatomic ions and one basedon nucleophiles—are included in the Supplemental Materials.W

Creating the Puzzles

Since the learning goal was increased usage of and at-tention to detail for the symbols themselves (rather than theproblem-solving logic of the puzzle), the easiest puzzles avail-able were chosen such that they could be solved solely byinspection. The difficulty level for a puzzle often accompa-nies published puzzles. To transform a numerical 9 × 9 puzzleto a chemical one, an instructor must generate a list of ex-actly nine chemistry items or symbols. Each symbol is as-signed to one of the numbers that appears in the puzzle andthe numerical “givens” are substituted with the correspond-ing symbol or symbol name. We used a chemical drawingprogram (7) to build a blank 9 × 9 grid from which eachindividual puzzle could be created.

An additional feature can be used that takes advantageof the experience we have as puzzle solvers. Before makingsubstitutions, the puzzle was solved in such a way that allnine instances of a particular number could be completedbefore going to the next number so that the chemistry puzzlescould include a suggested order of solving to reward studentswith the appropriate chemical knowledge. Thus a hint is givenfor the functional group sudoku shown in Figure 1 that if thesymbols are filled in starting from the highest to lowest pri-ority group in IUPAC nomenclature (8), then the puzzle willbe solved more readily. Thus the solver should start with thecarboxylic acid functional group. An examination of the topmiddle box of Figure 1 reveals three blanks and six “givens”.The upper-left blank should be filled in with a carboxylic acidsince the remaining two blanks in that box already have a car-boxylic acid listed in those rows. If students were to randomlychoose a different first functional group, they would likelyfind that more than one possibility for a certain space andsolving the puzzle would take more time and effort. For in-stance, attempting to start with an aldehyde or amide in thetop middle box would only allow the solver to narrow thepossibilities to two of the three blanks, rather than definitivelyfilling a blank. Therefore this strategy of providing chemicalhints rewards those with appropriate chemical knowledge.

Results

Informal student feedback indicates that assigned puzzleswere generally helpful in learning the chemistry and weremore enjoyable than traditional rote methods of memoriza-tion. Some students said the puzzles forced them to learn thechemistry faster than they would have otherwise. There werea number of students who had seen, but never solved, a sudokupuzzle before and were thankful to know what they were andhow they worked. To date our use of sudoku puzzles has been

Chemistry for Everyone

www.JCE.DivCHED.org • Vol. 84 No. 4 April 2007 • Journal of Chemical Education 613

to offer them as optional, take-home assignments that arecollected at the next class period. As motivation to completethis optional assignment, students who complete the puzzleare then exempt from the quiz covering the same materialpresent on the puzzle. The puzzles can be graded by examin-ing a handful of squares to ensure that the proper symbol ispresent, as a mistake in one location usually results in severalmisplaced symbols. When the puzzles are assigned, a fewminutes of class time can be used to show the necessary strat-egy, while a link on the class Web site to puzzle-solving guidescan assist students outside of class (9).

In our experience most students actually used the chemi-cal symbols to solve the puzzles. In rare cases evidence sug-gests that students have assigned numbers to each symbol,solved the puzzle with numbers, and then taken the solvednumerical puzzle and filled in the appropriate symbol. Sucha strategy defeats the stated learning purpose of the chemis-try puzzle whereby students were to benefit from the repeti-tion of working with the chemical symbols and names.

Conclusions

Students appreciate “fun” ways to do boring tasks suchas memorizing fundamental chemical vocabulary. Sudokupuzzles provide such a method. The ready availability of puzzletemplates and the ease of making substitutions allow this as-signment to be incorporated in the classroom with minimaleffort. To create puzzles with a suggested order of completionrequires more preparation time and some expertise in puzzlesolving such that good suggestions can be provided.

WSupplemental Material

The answer to the functional group sudoku and two ad-ditional sudoku puzzles and their answers (anions and nucleo-phile) are available in this issue of JCE Online.

Literature Cited

1. Helser, T. L. J. Chem. Educ. 2005, 82, 552.2. Kelkar, V. D. J. Chem. Educ. 2003, 80, 411–413.3. Most, C. J. Chem. Educ. 1993, 70, 1039–1040.4. Sudoku Home Page. http://www.sudoku.com/ (accessed Jan

2007); provides puzzles to many newspapers and sells soft-ware for Windows computers that will create a sudoku puzzle.

5. Web Sudoku Home Page. http://www.websudoku.com/ (accessedJan 2007); contains nine-by-nine as well as alternative gridsudoku puzzles.

6. Riddick, D. Chemistry Su Doku; RSC Publishing: Cambridge,2005.

7. ChemDraw Ultra version 7.0 by CambridgeSoft. http://www.cambridgesoft.com/software/ChemDraw/ (accessed Jan2007); used to construct both the grid and the chemical sym-bols.

8. Priority of organic functional groups is normally listed in in-troductory organic chemistry textbooks such as Bruice, P. Y.Organic Chemistry, 5th ed.; Pearson Prentice Hall: Upper SaddleRiver, NJ, 2007; p 791.

9. Wikipedia: Sudoku. http://en.wikipedia.org/wiki/Sudoku (ac-cessed Jan 2007); describes numerous logic methods for solv-ing a sudoku puzzle.

Figure 1. Functional group sudoku. Answers are available in the Supplemental Material.W