The Mole Concept Developing an Instrument To Assess Conceptual Understanding Shanthi R. Krishnan 8001Chend Coltina Trail, austin, TX 78749 Ann C. Howe
Department of Curriculum and Instruction, University of Maryland, College Park, MD 20742 Research on students' alternative frameworks in science describes a method for developing a paper and pencil test to evaluate students' understanding of the mole concept" and the recent advances in cognitive psychology have emphasized that leaming takes place within the context of in chemistry. The development of this instrument was already acquired knowledge. This realization has caused based on research regarding students' understanding of science educators increasingly to be concerned about the the mole concept and was revised upon piloting and Furknowledge held by the students prior to instruction ( 1 4 ) . ther reviewing. The development of this instrument was based upon Treagust's (12) work, with modifications incorWhen these prior conceptions are misconceptions, then porated to accommodate for the scope and nature of the they prove to have a detrimental effect in problem solving topic under study. (5)and course performance (6). One of the most important aspects of research in science Research Method education is directed toward gaining a better understanding of the difficnlties that students have in learning The development of the diagnostic test wnsisted of four science. Research indicates that students' difficulties in main stages that are explained in a greater detail in the learning science wnmpts is due in part to the teachers' following sections. lack ofknowledge regarding students'prior understanding of wncepts under study (1, 4). Stage 1. Defining the Content Students'conceptions that are different from those held This stage involved the identification and careful study by the scientific community have been labeled as "misconof the defmition of the mole concept as defined in popular ceptions", "preconceptions", "alternative frameworks", or chemistry textbooks. Then the mole concept was redefined "children's science". One way of understanding students' as statements, each statement involving only one variable. conceptions t h a t h a s been employed widely is the The next stage was to identify the way in which each of Piagetian individual interview method. Osborne and Freythese derived definitions of sub-concepts may be used in berg(7) and Watts (8)have described a variety ofinterview problem solving involving the mole. The concept map preformats or procedures for conducting these interviews. sented as Figure 1developed by Gower, Daniels, and Lloyd Though shown to be effective, this method still is not ac(13) was used to validate these derived definitions. This c e ~ t e dreadilv-bv.teachers. because. in addition to being concept map is composed of such related concepts as extremely time-consuming, it also demands expertise in order to interpret and MOLE CONCEPT analyze the results. 1 1 Individual instruction also has beenused I Shorthand I successfully as a method for correcting misrepresentation conceptions by Lavie and Novak (91, but it of pure substances has the same disadvantages as the interview method. One tool that would be readily used by the teachers would be a paperpencil test specifically designed for the purpose of identifying misconceptions. Such a test then could be used as a diagnostic tool to guide the teacher toward addressing students' misconceptions revealed through instructions specifically designed for the purpose. Such diagnostic tests have been developed by Peterson (10) in covalent bonding in chemistry, Haslam (11)in biology, and Treagust (12) in both covalent bonding and structure in chemistry and in photosynthesis and respiration of plants in biology These tests contain two-tier multiple-choice items that are not suitable for all concepts in science, particularly those in physical science that require formal application of concepts in problems. Treagnst (12)gives a detailed description of the method he used for developing a test for diagnosing misconceptions. This paper Figure 1. Mole wncept map. Volume 71 Number 8 August 1994
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atomic mass and molecular mass, as well as the application concepts of molecular formula and svmbols. therebv indicating'the relationships between theauhsunkn(: cmcepts and the unilWna mole concern. The identified definitions also were vaiid&d by science educators and chemist r y instructors in regard to scientific accuracy and contextual limitations of the mole concept used in this study. Stage 2. Defining Learning Objectives
These questions consisted of a simple statement with a multiple-choice of four answers for each statement. The four answers began as true or false followed by a reason. Students are not only required to take a stand on whether the statement is true or false but also to explain their reasons for saying so. That way one can understand the reasoning of the students. Example 2 . One mole of oxygen molecules contain more indethan ) one mole of oxygen atoms (0). pendent units ( 0 ~
The next s t e was ~ to redefme the definitions in the form of learning objectives so that the test items may he developed in order to test these obiectives. The overall definition o? the mole concept was first stated as five sukoncepts. Each of these subconcepts was then restated as a learning objective. These objectives were then reviewed and revised and the final statements of the objectives are as follows. Objectiue I . The student will know that the male is a counting unit and that one mole of any substance wntains the same number of units as one mole of any other substance. Objwrrue 2. The atudent will know that the male is defined as the amount ofsubstancr containing Avogadro's number uf units or particles of that substance. Obiective 3. The student will be able to recwnize that the atomic ratios in the formula of a molecule is also the molar ratio of atoms in that molecule. Obieetiue 4. The student will be able to calculate the atomic or &oleeular masses in grams fmm the molai masses of the respective atoms or molecules, and vice-versa. Objective 5 . The student will be able to relate the molecular emrdinates in the balanced equation with the molar ratios of the molecules of reactants and products.
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npe 2. no-Tier Pue-False Questions with Reasons
Stage 3. Research on Students' Misconceptions in the Mole Concepl
This stage involved a detailed review of previous research studies that focused on students'mismnceptions in the mole concept. Considerable work has been done reeardine students' understandine of the mole concent (1419). K e misconceptions identged in these stud& were compiled in a list to be used in developing items in the diagnostic test. The prepared list of misconceptions were presented to experienced chemistry instructors who validated them as true misconceptions if held by students.
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(a) True, because there are two atoms of 0 far every molecule of Oz. (b) True, because one mole of OZweighs more than one mole of 0. (c) False, because both of them have the same number of particles. (d) False, because one male of 0 has the same mass as one mole of 02.
Here again the distracters in the choice of answers were developed based on the list of misconce~tions.There were two such items in the test. npe 3. %o-Tier Multiple-choice Items
In this cateaow, - -. the students were asked a auestion and given a choice of four answers to pick from. 1; addition to this they were also asked to state reasons for their answer choice in their own words. Erample 3. Circle the letter corresponding with the best" answer for each of the fallowing questions and give reasons for your choice. One molecule of sulfur contains 8 S atoms. Then one mole of sulfur malecules will wntain (a) 8 g of sulfur
(b) 8 moles of sulfur atoms (c) 6.02 x loz3sulfur atoms (d)8 sulfur atoms Reason:
There were five such items in the final instrument.
Ope 4.Problems In this category, the students were presented with a problem that required mathematical calculations to arrive at an answer. The students were required to illustrate clearly their calculations and circle the answer.
Stage 4. Developing the Test Items
The next step was to develop test items for the learning objectives that were defined in stage 2. It was realized that anv one t m e of question would not cover the entire scope of ;he m o i ~ c o n c runder ~t study. Hence, it wasdecided thst four types of test Items would be used and that the identified misconceptions would be used as distracters or as othenvise appropriate in the test items. The four types -. of test items used are as follows. o p e I . Simple Multiple-choice Questions These items tested the basic definition of the mole concept. The distracters used in these multiple-choice items wire based on the list of misconceptions. Emmple 1 . A mole of HzO and a mole of O2 (a) have the same mass (b) contain one molecule each (c) have a mass of 1g each (d) contain the same number of molecules
There were three items in this test that fell under this category of questions. 654
Journal of Chemical Education
Example 4. Each carbon atom wntains 6 electrons. How many carbon atoms will contain one mole of electrons? Answer:-
Calculation:
There were 10 such questions in the final version of the test. In these questions, the teacher is encouraged to pay attention to the students' methods of calculations rather than their answers in order to understand their trains of thought. This also enables the teacher to determine whether the students have difficulty in combining two simple steps in a complex problem. Example 4 is an example of a simple problem. Example 5 is an examole of a more complex~roblem. Example 5 . How many grams of NaHC03 will react to form 10.0 g of Conin the following reaction? NaHC03 + HCI + NaCl+ HZO+ COz
The final version of this diagnostic instrument, which consisted of 20 items was arranged as represented in Figure 2. This version along with a copy of Figure 2 was presented individually t o an expert committee consisting of two university chemistry professors, four high school
The students' choice of (a) indicates that students have an incomplete understanding of what the term "independent units" in the definition of "mole", stands for, as opposed to the number of atoms in a multi-atomic molecules. This misunderstanding is prevalent even in sophomore chemistry majors. The students'choice of answer (b) is consistent with literature available on students' misconceptions stating that students often believe "mole" to be an exclusive property of the molecules and not the atoms. This misconception is similar to that reported by Novick and Menis (14) and Cervellati, et al. (161, which states that students considered that one "mole" of any substance always related to a certain number of "moleeules" of that substance. Choice (dl, apart from differentiating those students who have acquired the concept of mole as being a counting unit from those who have not, also serves the second purpose of identifying the misconception that students commonly have regarding the confusion of the term "quantity" in the definition of mole as meaning a "wnstant mass" rather than a "constant number". It must be noted that these misconceptions, although found com~arativelvless often. are quite-prevalent even in sophomore chemistry majors, thereby substantiating the difficulty of c h a n- h g - these misconceptions through regular instrktion. The instrument thus developed is ready to be used in classroom in order to diagnose students'eo&eptual understanding of the mole. Then this will enable the teachers to ~ l a and n desien their instructions in order to address the ~~~~~ - - inconsistencies in students' conceptions in mole concept. Through this article, we have not only presented a paper-pencil test instrument for diagnosing misconceptions in Mole Conce~t.but also we have ~rovideda detailed description of t h l method used in thCpreparation of this instrument. This will enable future researchers and teachers in order to prepare a similar paper-pencil test that could be used to diagnose miswnceptions in other concepts. A copy of the instrument "Mole Concept Test" is available from the one of the authors (SRK).
CONCEP~
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SUB-CONCEPTS -)
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LEARNING
OBJECTNES
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TESTITEMS (4 itemsforeach learning objective)
List of misconce~tions identified in each item. Figure 2. Distribution of the test items in the Mole Concept Test. Students' Selection of Answers to Example 2
Class
Students' Choice of Answers in % a
b
ca
d
15
5
70
10
Introductory Chemistry (6) 25 ?3atands for the correct answer.
5
50
20
Chemistry Majors(A)
chemistry teachers, four graduate science education students. and two chemistrv laboratom instructors. Their suggestions and comments were analyzed and incorporated in the revised version of the instrument. This revised version of the instrument was administered to a group of 20 chemistm maiors in their so~homorevear in wlleee. The data t l k s obtained were used to an item analysis on the instrument. An estimate of the reliability of the instrument was determined by calculating the Kuder-Richardson's reliability coefficient that was found to be r = 0.81. The difficultyanddiscrimination indices and the point biserial coefficient also were determined for each item in the instrument. They were found to fall within the acceptable range of O.PO.8 for difficulty index, 0.46- 0.86 for discrimination index, and 0.22-0.68 for point biserial coefficient. This final version of the Mole Concept Test (MCT) also was administered to 20 volunteers from an introductory university chemistry course. Analysis of an Example
The performance of these students in Example 2 (given above) is presented in the Table and discussed in order to illustrate how the instrument and the resulting data can be used by chemistry teachers. If this had been a simple truefalse item, it can be noted that 80% of studentsfiom class Aand 70% of students from class B had the correct answer because the answer would then be "false". Upon the introduction of the reason statement, it was possible to see that only 70% of students from class A and 50% of students from class B had the correct response.
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Literature Cited IDriver, R.; Easlqv. J. Stud. Sci. Edur 1978.5,61-84. 2. Driver R.: Erickson. G.Stud &i. Edue 1988.10 8 7 a
6. Champ~ne,A.B.:I(lopfopf,L.E.:Anderm, J.H.Am. JPhys. 1880,48,107P1019. 7. Osbome, R.;Freyberg, P Learning in Science The Implimfions of ChildrPnS Scion-;
Heinernan" Publishers: New Hampshire, 1980.
8. Watts, M. Ropmsmlotion ofPhysics and Chemistry Knomledgo. Ludwigsburg West
Germany, 1981,365-386, 9. Navak, J. DP~ocPPdingsoflhelnfomotionolSeminaron Miiiicepfians in Mothemol&andSckn~%Ithaen, New Yark, 1983.
10. Peterson, J. Unpublished masters thesis, Curtin University of Pchnology. Perth, Australia, 1986. 11. Haslam, F Unpublished masters theis. Cvrtin University ofl!echnology. Perth, Australia, 1987. 12. Reaguof,D. E in,. J.Sci. Educ. 1988,10(2J,159-169. 13. Gower, D . M.; Daniels, D. J.; Llqvd, B.Sch. Ser. Mu.1977,58,667. 14. Novlck,S.;Meni% J. J. Chom.Educ. I976,53I11J,72G727. 15. VincentA.Edue. Chem. 1981,18. 114. 16. Ceruellati.A. JCham. Educ. 1882,59(101,852856. 17. Howe, A. C.; D m , B. P. J Ilrs Sci. Tpoeh. 1982,109(3),217-224. 18. ME M a n s , F. REdm. Chem. 1983.20.6. 19. Morris,J. E.; Waddin8ton.D. J.Edue. Chom. 1982,July,37.
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