a solution to stoichiometry: teaching problem solving in chemistry

7/16/2019 A Solution to Stoichiometry: Teaching Problem Solving in Chemistry

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A Solution to Stoichiometry:Teaching Problem-Solving in Chemistry

Douglas Le, Secondary Science MAT



Introduction

Placed at William M. Davies Jr., Career &Technical High School in Lincoln, RI

All students are in a 4-year academic program,as well as a 4-year technical program

Taught the only 2 sections of 11th gradeCollege Prep (CP) Chemistry



Introduction

Chemistry can be challenging, especially givenwhat is covered in a traditional high schoolcourse (Deters 2006)

One of the most abstract yet fundamentalconcepts covered in high school Chemistry isstoichiometry (BouJaoude 2003)



Introduction

Stoichiometry: “the proportional relationshipsbetween two or more substances during achemical reaction” (Myers 2006)

Stoichiometry: calculations that involve theamount of substances in a chemical reaction(Le 2013)



Introduction

Stoichiometry is difficult for various reasons(Haidar 2008)

Students around the world have difficultylearning stoichiometry…and teachers havetrouble teaching it! (BouJaoude 2003, Dahsah2007, Haidar 2008, Okanlawon 2010)

If so challenging, why choose this topic?



Introduction

My research aimed to answer two questions:

1)Does emphasizing units and dimensionspromote understanding and problem-solving in

Chemistry?2)Can a graphic organizer enhance students’

understanding and problem-solving inChemistry?

If yes, then students should be able to:1)analyze and solve novel stoichiometry problems

by focusing on the units and dimensions

2)adapt a graphic organizer to accommodatenovel stoichiometry problems



Methods & Materials

3 curricular units over the course of 1 quarter:Unit 1 (U1): Chemical Equations & ReactionsUnit 2 (U2): Solution ChemistryUnit 3 (U3): Acid-Base Chemistry

Decided to use a combination of two research-based methods for teaching stoichiometry(DeMeo 2008):

1) Dimensional Analysis2) Graphic Organizer



Methods & Materials

Dimensional Analysis (DA): conversion of agiven quantity from one system of units toanother (Le 2013) Conversion Factor (CF): “a ratio that is derived from the

equality of two different units and that can be used toconvert from one unit to another” (Myers 2006)

1 min = 60 s or1 min

60 sor

60 s

1 min

Example: How many seconds in 1 year?

1 y r ×365 d

1 yr×

24 hr

1 d×

60 min

1 hr×

60 s

1 min= 3,153,600 s



Methods & Materials

Graphic Organizer (GO)

Ault 2001, 2006 Adapted Version



Methods & Materials

Various pieces of student work and classassignments were assessed

While each assignment had a unique answerkey, all of them were assessed based on thefollowing two criteria:

1) Identification of appropriate CFs

2) Use of CFs in appropriate order

1 y r ×365 d

1 yr×

24 hr

1 d×

60 min

1 hr×

60 s

1 min= 3,153,600 s

21 3 4



Results

0

10

20

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40

50

60

70

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90

100

Diagnostic Assessment

% o

f T o t a l S t u d e n t s

Assessment of Student Understanding of Stoichiometry

Understood CFs Used correct CFs CFs in correct order



Results



Results

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Diagnostic Assessment Formative Assessment 1

% o



Understood CFs Used correct CFs CFs in correct order Used the GO



Results



Results

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Diagnostic Assessment Formative Assessment 1 Formative Assessment 2

% o






Results

One of the summative assessments was a two-question “survey” designed to answer the 2questions behind this project



Results



Results

0

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Diagnostic Assessment Formative Assessment 1 Formative Assessment 2 Summative Assessment

% o






Discussion

Overall there was a small but not verysignificant improvement in students’ ability tosolve stoichiometry problems

Results seem to indicate two main reasons forthe limited success:

DA relies heavily on CFs, but certain CFs are easier tounderstand than others

Inconsistent use and reinforcement of GO led tostudents not taking advantage of this tool



Discussion

Results of summative assessment had directimplications for the two research questions:

1) Does emphasizing units and dimensions promoteunderstanding and problem-solving inChemistry?

Not necessarily authentic understanding, more likely toenable a “plug and chug” mentality in students

2) Can a graphic organizer enhance students’understanding and problem-solving inChemistry?

Graphic organizers can help alleviate some of the “plug

and chug” mentality, but not likely to enhance their skills



Conclusion

Two possibilities for future directions:1) Revamp the DA/GO method

Be more consistent with GO

Use more relevant, real-life applications

2) Consider additional/alternative methods Symbolic Algebra (DeToma 1994)

Mole-Ratio Flow Chart (Wagner 2001) Reaction Tables (Watkins 2003)

Cross-Proportions (Cook 2005)



ReferencesAult, A. (2001) How to say how much: Amounts and stoichiometry. Journal of Chemical Education, 78 (10), 1347–

1349.

Ault, A. (2006). Mole city: A stoichiometric analogy. Journal of Chemical Education, 83(11), 1587.

BouJaoude, S., & Barakat, H. (2003). Students’ problem solving strategies in stoichiometry and their

relationships to conceptual understanding and learning approaches. Electronic Journal of Science

Education, 7 (3).

Cook, E., & Cook, R. L. (2005). Cross-proportions: A conceptual method for developing quantitative problem-

solving skills. Journal of Chemical Education, 82(8), 1187–1189.

Dahsah, C., & Coll, R. K. (2008). Thai grade 10 and 11 students’ understanding of stoichiometry and related

concepts. International Journal of Science and Mathematics Education, 6(3), 573–600.

DeMeo, S. (2008). Multiple Solution Methods for Teaching Science in the Classroom: Improving Quantitative

Problem Solving Using Dimensional Analysis and Proportional Reasoning. Boca Raton, FL: Universal

Publishers.

Deters, K. M. (2006). What are we teaching in high school chemistry? Journal of Chemical Education, 83(10),

1492–1498.

DeToma, R. P. (1994). Symbolic algebra and stoichiometry. Journal of Chemical Education 71(7), 568–570.

Haidar, A. H., & Al Naqabi, A. K. (2008). Emiratii high school students’ understandings of stoichiometry and the

influence of metacognition on their understanding. Research in Science & Technological Education, 26(2),215–237.

Myers, R. T., Oldham, K. B., & Tocci S. (2004). Holt Chemistry . New York, NY: Holt, Rinehart & Winston.

Okanlawon, A. E. (2010). Teaching reaction stoichiometry: Exploring and acknowledging Nigerian chemistry

teachers pedagogical content knowledge. Cypriot Journal of Educational Sciences, 5(2), 107–129.

Wagner, E. P. (2001). A study comparing the efficacy of a mole ratio flow chart to dimensional analysis for

teaching reaction stoichiometry. School Science and Mathematics, 101(1), 10–22.

Watkins, S. F. (2003). Applying the reaction table method for chemical reaction problems (stoichiometry andequilibrium). Journal of Chemical Education, 80(6), 658–661.



Acknowledgments

I would like to acknowledge the followingindividuals for their assistance in my research: Janet Butler

Ben Abrams Kerrie Medeiros and Tom Weaver Dan Bisaccio My students



Appendix: Student Work

a solution to stoichiometry: teaching problem solving in chemistry

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