Macro- and Micro-Chemical Comprehension of Real-World Phenomena Classroom Knowledge versus the Experience of the Senses Nava Ben-Zvi and Rivka Gai The Hebrew University, Jerusalem. 91904 Israel In recent years, studies in chemical education have fo- cused on a number of issues from policy making in curricu- lar development and implementation, through teacher- centered issues, to students' understanding, misconcep- tions, and problem-solving abilities. In our study we have dealt with two issues concerning high school students: the understanding of the nature of matter and the ability to analyze real-world phenomena (on both the macro and the micro level). Although these issues appear at first glance to he unrelated, closer inspec- tion reveals that the latter is heavily dependent on the for- mer. A number of studies have dealt with understanding the nature of matter. Staw (1.2) examined students aged 9-14 . . regarding the~r understanding of concepts such as solids, liauids. and aasei. She found misconce~~ions in then un- . . derstanding of the properties of matter, probably as the re- sult of faulty understanding of the structure of matter and the process of phase changes. Ben-Zvi et al. (3) found in- correct macroscopic and microscopic views among high school students about chemical concepts and chemical for- mulas. Gahel et al. (4) dealt with university students studying to be elementary school teachers and found that their conceptions of the particular nature of matter were far below the desirable level. Other studies were conducted regarding students'ahility to analyze real-world phenomena. Hnrd (5) and Renner (6) dealt with the importance of teaching science in a societal context. focusing on real-world ~henomena in students' lives. ~ ; a u n et a c (7) wrote against the curricula of the 80's which. althoneh using a societal approach to teaching sci- ence, bas aimed at science-oriented students, relying on their former conce~tual knowledge. In the 90's curricula there 1s a larger exposure to conr&ual knowlt~dgt~ of STS nature, aimed at w~der h~gh school pooulnt~uns 18.91 Bod- ner (10) found t h a t @-aciuate students *have difficulty, however, applying their knowledge to areas where they have not been actively encouraged to apply it. . .they can- not extend their knowledge beyond the limits of the class- room into the real world". We, too, support the educational philosophy that science learnina should be aimed at aiding students in under- standing the real world. In linewith chis belief we want to see high school chemistm studies ~rovidina students with a wideexposure to real-world phenomena based on a solid com~rehension of the nature of matter and its analysis hothat thc macro and mlcro level. We deemed it impo<ant to test the student's ability to dissect events also on the micro level even within one's high school studies. Micro level explanations are important for understanding chem- istry in general and daily occurrences in particular. Al- though those students who will continue to study chemis- try in the university will be helped to strengthen their micro level thinking, the majority of the students will cease their science studies after high school and thus we desire to maximize the usefulness of the high school classes. We decided to categorize answers according to their content level. either macro or micro. Macro approach refers to measurable phenomena, while micro appr&h re- fers to molecular interpretations. In an attempt to discover the extent that students are learning in this manner, we proposed the following re- search questions: 1. Do high school students comprehend the nature of matter both at the macro and the micro level? 2. Do students comprehend the transformation from one state of matter to another? 3. Can students recognize camman aspects ofvarious ehemi- cal phenomena? 4. In what ways do students analyze real-world phenomena? 5. Are there differences in the analytical ability of students studying STS-oriented curriculum, and those studying a concept building curriculum? Experimental Design Toward the end of the school year, six randomly selected 10th grade classes from five different locations in Israel were tested. All 170 participating students studied chem- istry three hours a week, using one of two textbooks, one (N=51) much more STS oriented than the other (N=119). For example, only the STS-oriented textbook has a chapter the hook'6 larmst that dwls with "Thc Qualit\ of Air". In it, the environmental issues serve as a vihicletoward the learnine of combustion reactions and oro~erties of materi- als, sucrh as oxides. None of the subjects were science ma- jors. Ninety-seven were humanity majors, while the other 73 studied in classes that had still not been separated into science or nonscience students. Prior to the testing of the six classes, a demonstration- based questionnaire was given to a single class of 25 stu- dents (The Pilot Phase). This structured questionnaire fol- lowed a demonstration of two closed test tuhes: one test tube contained two drops of acetone, and the second a small ~ i e c e of solid iodine. The test tuhes were then heated until a change of state was observed. The students were told to imagine they were using a microscope that can ex- plore thc &lo level. They were then asked to descril)e (at the m~cro level, both textual and graphically, the structure of the matter in both test tubes Inhrt. and i~ftrr the warn- ing. Based on the findings of this test instrument, a second paper-pencil instrument was developed and presented to the six experimental classes. All questions dealt with real- life events, attempting to probe students'understanding of processes that involve changes in states of matter, in terms of energy and entropy. (We intentionally chose situations which, although recognizable to the student, were not so common as to have a "personal" connotation that might ef- fect the potential answer.) Each question contained two multiple-choice parts. The first required a single choice, while the second was de- 730 Journal of Chemical Education
Transcript
Macro- and Micro-Chemical Comprehension of Real-World Phenomena
Classroom Knowledge versus the Experience of the Senses
Nava Ben-Zvi and Rivka Gai The Hebrew University, Jerusalem. 91904 Israel
In recent years, studies in chemical education have fo- cused on a number of issues from policy making in curricu- lar development and implementation, through teacher- centered issues, to students' understanding, misconcep- tions, and problem-solving abilities.
In our study we have dealt with two issues concerning high school students: the understanding of the nature of matter and the ability to analyze real-world phenomena (on both the macro and the micro level). Although these issues appear a t first glance to he unrelated, closer inspec- tion reveals that the latter is heavily dependent on the for- mer.
A number of studies have dealt with understanding the nature of matter. S t aw (1.2) examined students aged 9-14 . . regarding t h e ~ r understanding of concepts such as solids, liauids. and aasei. She found misconce~~ions in then un- . . derstanding of the properties of matter, probably as the re- sult of faulty understanding of the structure of matter and the process of phase changes. Ben-Zvi et al. (3) found in- correct macroscopic and microscopic views among high school students about chemical concepts and chemical for- mulas. Gahel e t al. (4) dealt with university students studying to be elementary school teachers and found that their conceptions of the particular nature of matter were far below the desirable level.
Other studies were conducted regarding students'ahility to analyze real-world phenomena. Hnrd (5) and Renner (6) dealt with the importance of teaching science in a societal context. focusing on real-world ~henomena in students' lives. ~ ; a u n et a c (7) wrote against the curricula of the 80's which. althoneh using a societal approach to teaching sci- ence, b a s aimed a t science-oriented students, relying on their former conce~tual knowledge. In the 90's curricula there 1s a larger exposure to conr&ual knowlt~dgt~ of STS nature, aimed at w~der h ~ g h school pooulnt~uns 18.91 Bod- ner (10) found that @-aciuate students *have difficulty, however, applying their knowledge to areas where they have not been actively encouraged to apply it. . .they can- not extend their knowledge beyond the limits of the class- room into the real world".
We, too, support the educational philosophy that science learnina should be aimed at a i d ing students in under- standing the real world. In linewith chis belief we want to see high school chemistm studies ~rovidina students with a wideexposure to real-world phenomena based on a solid com~rehension of the nature of matter and its analysis hothat thc macro and mlcro level. We deemed i t impo<ant to test the student's ability to dissect events also on the micro level even within one's high school studies. Micro level explanations are important for understanding chem- istry in general and daily occurrences in particular. Al- though those students who will continue to study chemis- try in the university will be helped to strengthen their micro level thinking, the majority of the students will cease their science studies after high school and thus we
desire to maximize the usefulness of the high school classes. We decided to categorize answers according to their content level. either macro or micro. Macro approach refers to measurable phenomena, while micro appr&h re- fers to molecular interpretations.
In an attempt to discover the extent that students are learning in this manner, we proposed the following re- search questions:
1. Do high school students comprehend the nature of matter both at the macro and the micro level?
2. Do students comprehend the transformation from one state of matter to another?
3. Can students recognize camman aspects ofvarious ehemi- cal phenomena?
4. In what ways do students analyze real-world phenomena? 5. Are there differences in the analytical ability of students
studying STS-oriented curriculum, and those studying a concept building curriculum?
Experimental Design Toward the end of the school year, six randomly selected
10th grade classes from five different locations in Israel were tested. All 170 participating students studied chem- istry three hours a week, using one of two textbooks, one (N=51) much more STS oriented than the other (N=119). For example, only the STS-oriented textbook has a chapter the hook'6 larmst that dwls with "Thc Qualit\ of Air". In
it, the environmental issues serve as a vihicletoward the learnine of combustion reactions and oro~erties of materi- als, sucrh as oxides. None of the subjects were science ma- jors. Ninety-seven were humanity majors, while the other 73 studied in classes that had still not been separated into science or nonscience students.
Prior to the testing of the six classes, a demonstration- based questionnaire was given to a single class of 25 stu- dents (The Pilot Phase). This structured questionnaire fol- lowed a demonstration of two closed test tuhes: one test tube contained two drops of acetone, and the second a small ~ i e c e of solid iodine. The test tuhes were then heated until a change of state was observed. The students were told to imagine they were using a microscope that can ex- plore thc &lo level. They were then asked to descril)e (at the m~cro level, both textual and graphically, the structure of the matter in both test tubes Inhrt. and i~f t r r the warn- ing.
Based on the findings of this test instrument, a second paper-pencil instrument was developed and presented to the six experimental classes. All questions dealt with real- life events, attempting to probe students'understanding of processes that involve changes in states of matter, in terms of energy and entropy. (We intentionally chose situations which, although recognizable to the student, were not so common as to have a "personal" connotation that might ef- fect the potential answer.)
Each question contained two multiple-choice parts. The first required a single choice, while the second was de-
730 Journal of Chemical Education
signed to probe the type of explanation given by the stu- dent for the phenomena. The subjects were told explicitly that although, in the second part, more than one answer could be considered correct, they were to choose the answer which, in their opinion, is most fitting. ( Both correct and incorrect answers could relate to either the macro level or to the atomic "microscopic" level.)
The following question exemplifies the general structure of the questions:
1. Shortly afterputting a drop ofacetone on your hand, you feel a cold sensation. (choose one) [ I The drop of acetone remains a liquid. [ 1 The drop of acetone changes to a gas.
The best explanation is: (chaase one only) [ I A. The acetone cools the hand. [ ] B. The hand gives energy to the acetone. [ I C. The temperature of the acetone drop is lower
than the temperature of the hand. [ I D. The molecules of the acetone receive energy.
Results and Discussion
Table 1 relates to the Pilot Phase. I t presents the distri- bution of the students on the preliminary, demonstration- based questionnaire regarding a particulate description of matter, textual, andlor graphically, regarding separately the acetone and the iodine. When a student gave a micro explanation, both textual and graphically, we labeled it as a constant particulate view, a micro explanation given either textual or graphically was labeled as a partial par- ticulate view, while students who didn't give any particu- late description were described as lacking a particulate view.
While all students have been taught the particulate model of matter in their iunior hieh school General Science ~~~~~~~~~ ~ .. course, about a third (2d':-36Ur1 fiiilctd to demonstrate any knowledrrtr of the osrticulatr structure of matter. This lack of demonstration'possibly can be explained by the diffi- culty students have in utilizing the models and explana- tions acquired in the classroom to analyze real-world phe- nomena. The auestionnaire for the main study was designed so as to pro\ide a better ability to accept (11. reject the explanation formulated in the l'ilnt Phase. Table 2 pre- s m t i the percentage of studcnts who chose the correct an- iwer fur the tirst part of a question, and the distribution of the macro micro anhwcrs in the second pan fur those who answered part 1 correctly rsee earlier example question,.
In the first qurstion !exemplified earlier, most of the stu- dents succredt,d to identiti the phenomenon 181'; I. Still, 56.8% of them gave an inapprodriate explanation (C), in- correctly claiming a temperature difference between the drop of acetone and that of the hand. This choice of expla- nation reflects a naive and intuitive level devoid of the use of any knowledge of structure and energy. The students ex- hibited difficulty in analyzing the phenomenon on a chemi-
~ -
cal basis. Of those who succeededthe orimarilv correct ex- ~ - ~ - ~~~~-~ ~
planation was a t the macro level, revealing an apparent ability to analyze carefully phenomena, coupled with a hesitation for further probing.
The second question deals with the possible change of state when water is heated from 20 "C to 30°C. At least
curri 1. -The curriculum with concept building approach cur". - The curriculum with the STS approach
40% of the students answered incorrectly ("all water re- mains liauid"). It is our sueeestion that most students tend -- to relate change of state-liquid-to-gas-only to water a t the boilingpoint, as stated elsewhere (2,ll) . Over 80% of those who answered correctly, appear to have internalized the particulate model of matter (micro view).
The third question deals with the possible dispersion of bromine into a closed vessel of air. Over two-thirds of the students answered correctly ("bromine gas is dispersed into the closed vessel of air"). More than 50% of those an- swering correctly supplied a correct micro explanation, with about half of the rest supplying a correct macro expla- .. ~ -
nation. The fourth question deals with the possible dispersion of
a poisonous gas to the upper floors of a tall building. Only about a third of the students answered correctly ("the poi- sonous gas rises to the upper floors") and a comparatively low percentage of those answering correctly gave a correct micro explanation.
Regardless of cumculum, we found a similar pattern of resp&e to those questions that focused on cherhicals pri- marily studied in school ($1 and $3). Students in both cur- ricula had a better understandingof phenomena taught a t school (68%-85%) than of those that they only know about from real-world experience (34%-$4).
I t can be safely stated that students' "chemical knowl- edge" of water r@2, is based on real-world trxpenence com- bined with hea\y exposure 11, the topic in the class room. In this auestion the students exhibited =eater difficultv than in 'Q1 and $3 but lesser difficultyyhan in Q4. ~ h k great majority of those who succeeded also demonstrated a correct micro view, probably acquired through classroom discussions of water in its three states of matter.
Apparently, the ability to transfer classroom type analy- sis to real world phenomena is a t least partially subject matter dependent. If we preach a STS-approach in our teaching, we have to ensure a variety of classroom expo- sures to chemical phenomena coupled with experiences from the students'own world, so as to strengthen students' micro level analytical abilities.
Table 3 presents our findings regarding the ability to rely on the senses in the analysis of changes in the state of matter, as well as to microscopically or macroscopically ex- plain the changes.
Questions 5 and 6 relate to whether the s h a r ~ smells of acetone (Q5) and moth balls (66) signify the existence of a eas. Question 7 deals with the chanee of state when iodine - " - is heated and a violet color is observed.
We found t h a t s tudents exhibited a better under- standing of liquid-to-gas change of state (80%-91%, Q1, $5) than of solid to gas change of state (53%-69%, Q6, Q7). Apparently, students didn't associate the sensual stimuli
Volume 71 Number 9 September 1994 731
Table 3. Use of Senses to Analyze Phenomena Table 4. Differences of Responses by Class Type
c.rr 1 Tne a r r CJ Jm wth concept -0, 0 ng approacn cJrn 2 Tne cur. ncu Lm wrtn the STS approach
with the chemical interpretations. In general, the same ob- servation made by Bodner (10) also applies here-"students do not extend their knowledge beyond the limits of the classroom, into the real world. . . ." These findings further exemplify our previous stated claim to the need for careful selection and integration of classroom topics with real world experience.
a b l e 4 presents the results of the t-test for three as- pects: knowledge, macro view, and micro view, for students in nonscience (Group 1) and "general" classes (Group 2). As stated, the "general" category consists of those schools in which there is no division of science and nonscience stu- dents in the 10th made.
The mean knowledge score (5.5-6.1) simals that a large portion of the subject had difficulty relating scientific ex- planations to familiar phenomena. This indicates difficul- ties in the ability to analyze real-life changing systems in respect to the determining factors a t both the macro and the micro levels. Still, almost 70% of those who gave a cor- rect answer to the question "what happens?" (part 1) suc- ceeded to find either macro or micro explanation for "how or why i t happens?" (part 21, with a stronger tendency to use micro explanations than macro ones. So, those who knew, usually knew well.
The significantly lower score of the nonscience group mav he explained by the fact that those concepts relevant foranalyzkg the tested phenomena are not ta ight in high school to the nonscience students. These findings provide much food for thought about topic selection in the high school curricula.
Tahle 5 presents the results of the t-test for the same three aspects: knowledge, macro view, and micro view, but this time according to the two different curricula.
While there was a significant difference hetween the two classroom types, (Table 4) neither of the two curricula led to a significantly better (5.7-6.0) or different under- standing of the phenomena. Still the students who studied the STS-oriented curriculum have a significantly higher preference for a micro viewpoint for analyzing the chemi- cal systems.
Further Discussion and Recommendations In studying high school students' understanding of the
nature of matter and their ability to analyze real world phenomena, we have arrived a t the following findings:
1. There is a genuine difficulty to translate "classroom knowledge" into the comprehension of real-life phenom- ena.
2. Conceptual knowledge, while at alevel which leaves much to be desired, often is not directly applied by students to
Item no. of mean S.D separate variance cases estimate
t value 2-tails pmb.
Knowledge
Group 1 97 5.5 1.8 -2.42 0.016 Grouo 2 73 6.1 1.4
Micm
Group 1 97 2.7 1.6 -2.08 0.039 Grou~ 2 73 3.2 1.9
Macm
Group 1 97 1.2 1.1 -2.00 0.048 Group 2 73 1.6 1.2
The following aspecls were defined as: Knowledge - The number of correct answers to 10 defined questions: the maxi- mum score=lO. Micro - The number of times that the studsnt used a micro exdanation for the
even! w In a corran answer to the 1 a pan Macm - Tne nJmber of !.me$ tnat tne stddent useo a macroexpanat~on tor the even! w in a conect answer 10 ths Is! pan
Table 5. Difference of Responses by Curriculum Type
Item "0. of mean S.D. separate variance estimate cases
Curriculum 1 is concept building and Curriculum 2 is STS oriented.
phenomena even when sensual aspects are heavily in- volved.
3. It seems that the ongoing emphasis on chemical concepts with which to understand real-world phenomena is of greater pedagogic importance than the type of curriculum in which thev are taueht.
4. Nevertheless, an STS-oriented curriculum, with a strong emphasia on the interrelationship between scientific con- cepts, dealing both in the macro and micro worlds, and real-life phenomena may better serve nonscience stu- dents' whose "limited" scientific knowledge is necessary to prepare them as future citizens.
The full questionnaire may be obtained upon request from the above address.
Literature Cited
1986,102. 6. Renner, J S c i . Edue. lJ88,66(5),709. 7. Braun, E.: Gibbons. M.; Williams,B. E k B u l t P n ;
London: Butterworth, 1911. 8. CHEMCON: Ame"can Chemical Society. hbuque. IA: Kmdall Hunt, 1985. 9. SATIS; Hatfield, He&, Association for Science Education, 1986.
10. Bodner. G. M. J. C k m . Educ. 1991.68.385. 11. Osbome, R.; Cosgove, M. J Sci. %h. lSW,ZO, 826.
