Microscale Laboratory at the High School Level Time Efficiency and Student Response Patrick McGuire E. Jefferson High School, Metairie, LA 70001 James Ealy Peddie School. Hightstown, NJ 08520
Miles pickeringl Princeton University, Princeton, NJ 08540 One of the major innovations in laboratory teaching in thn ~ a sten t vears has been the introduction of microscale work, first in adlegc organic laboratories and more recently in hiah schools cl-?). The advantages rlaimed for this new method are reduced cost, improved safety, and increased speed. A controlled study showed an increase in time efficiency a t the college level (41,but there has been little research at the high school level. We do not know how much time is actually saved doing representative experiments microscale, and we have no formal information about student attitudes toward this kind of laboratory experience. The attitudes are important due to the link between attitude and achievement (5).Also, studies have shown that lab work is important in molding attitudes toward science (6). We studied a representative group of high school students who did both the macro version and the micro versions of the same experiments. We report data on the completion time of the experiments, and on how scale affects student attitude. ~~~
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Table 1. Characteristics of Population
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Method This work was done a t E. Jefferson High School, Metairie, Louisiana, with students enrolled in first-year chemistry classes. This high school is a suburban, predominantly white, middle-class high school. About 30% of students continue to some form of higher education. The students in this study are all college-bound. AU students were taught by one of the authors, Patrick McGuire. Three experiments were carried out in both the macro version and the micro versions.
Average Scores Comprehensive Test of Basic Skill Percentile scores
' Author Miles Pickering is deceased
Group 2 (Micro before Macro)
Reading Language Math Battery Reference Skill Science Reading Soc. Sci. Reading Average Chemistry Grade 14.0 scale) sequences is reported, so that practice effects can be isolated. To learn if students preferred microscale to macroscale, they were asked to rate the experiments on various criteria. We also collected data on student overall preferences among the various experiments. Results and Data Reduction To study possible practice effects, we constructed two matched subgroups of the students. The only difference was the seauence of the macro version and the micro versions of the kp(!nment. 'me criterion of matchmg was the math subscore of the Com~rehensiveTest ol'lhsic Skills ICTW This subscore showLda correlation (r = 0 . 5 3 , ~< 0.001) with the average chemistry grade over the three marking periods just prior to the beginning of this study. The mathscore showed higher correlation than the other CTBS scores. This result agrees with the work of Arter (9). The characteristics of the two subgroups are shown in Table 1. Statistical testing of the two groups showed the probability that the two subgroups were identical: 0.99, using the math CTBS criterion; and 0.95, using the grade criterion. This similarity is important if the experiment is to be well-controlled. The time data are shown inTable 2 for each subgroup and for the whole population of students (regardless of sequence). This table also lists the percentage of the macroversion time that is saved if the micro versionis used. There is some variability in the number of students doing a given experiment due to absences, etc. ~~
The microscale version uses droppers or pipet (Beral), with drop counting as a volume measurement. It uses plastic multiple-well plates rather than glassware. For the synthetic experiments, 0.5 g rather than 5.0 g of potassium oxalate is used. Students were asked to record their time a t crucial steps in the sequencesof experiments. This allowed us to exclude time used for data reduction, even though students were expected to turn in reports a t the end of the period. For the synthetic experiments, crystallization time was omitted, as it was highly variable and depended on factors that were not well-controlled (e.g., dust on glassware). Students were put in one of two sequence groups, depending on whether they did the macro version or the micro version of an experiment first. Completion time for both
Group 1 (Macro before Micro)
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Table 4. Results of Poll of Students
Table 2. Time for Laboratory Operations
Students Choosing Experiments as
Time (min) N
Macro
N
Favorite
Time Saved
Micro
(W Continuous Variation
Least Favorite
Micro Experiments Continuous Variation
0
11
Group 1a
30
30.326.20~
28
15.6k3.07~
Titration
3
30
Group Za
30
28.524.08
28
19.9249.6
Synthesis
16
4
All
98
29.725.58
94
17.324.85
Any Micro Experiment
19
45
Students
Macro Experiments
Titration Group 1a
27
41.2212.2
26
19.3k4.88
Group Za
29
32.7k8.69
29
29.02937
All
96
35.6210.2
92
Continuous Variations
24.629.32
Students Synthesis Group 1
19
60.0217.2
23
44.629.69
Group Za
18
56.42122
23
50.3k11.5
All
64
59.72172
77
49.8213.2
10
10
Synthesis
34
5
Any Macro Experiment
48
17
No response (did not do all experiments)
41 6.57'
6.66'
"Significant at the p c 0.02 level
Student preference data were collected using a five-step rating scale. Each student was asked to agree or disagree with characterizations of the experiment: "easy", ''fun?, "took too long", "interesting", and "increased understanding". The negative attribute was used to avoid response-set effects. The positive attributions were combined, and the negative one subtracted, to get a n overall score with a 20-point range. Since there were wide variations between students in their reaction to the laboratory experience as a whole, we subtracted each respondent's rating on the macro lab from the same person's rating of the wrresponding micro version of the same experiment. Thus, each student acts a s his or her own control. Negative scores on the rating of the macro version vs. the micro version indicate a preference for the macro version. Positive scores indicate a preference for the micro version. These data are summarized in Table 3. They are also broken down by gender and other subgroups. Table 3. Results of Likert Scale Perference Measurement
All students
60
-1 .867a26.51
Males
32
-2.8Ia k7.52
Females
28
-0.78
Above mean CTBS score
34
-2.557a26.98
Below mean CTBS
26
-9.62
Journal of Chemical Education
Titration
(microversion vs. macro version )
'Group 1 did the macro version first, and group 2 did the micro version first for all exoeriments. %tanbard deviation.
870
2
X2
Students
'statistically significant at p < 0.05 bstandarddeviation 'Po~itivenumbers indicate Dreferencefar the micro version.
4
25.03
25.83
As a check on this measurement of student preferences, a summary form was filled in by students, who were asked which of the six experiments they most liked and most disliked. Explanations for the preference were requested. Some students are listed a s nonrespondents usually because they did not complete all six experiments. This data is presented in Table 4. I t is important to remember that our results on time efficiencv and on student attitude aoolv onlv to this oarticular set (")fexpenmcnts.while we bch& these to beiypical ofthoiedonr in high school labs. it is certainlv wssible that there may be othe; laboratory experiments &;which these conclusions do not apply Replication of this research a t other schools might also give additional information. Caution should also be used in extrapolating this study to college labs with students that are more experienced. Discussion We will discuss separately the time studies and the preference data.
Time Studies The data in Table 2 show that the macro version took more time than the micro version, but the effect varies widely with size. A striking time savings seems possible with the coutinuous variations and titration experiments, but the time savings is much less marked with the synthetic experiment. The amount of time saved was comparable to that in the college-level labs previously studied (4). There was a pronounced practice effect. As expected, this appeared most clearly on the first pair of experiments. The time required for the macro version was the same whether it was done first or second, but the time required for the micro experiment was vastly reduced when i t followed the macro version. For the other two experiments, the micro experiment was again faster if it followed the macro version, hut the macro experiments also showed comparable improvement if second in the paired sequence. ARer the first pair, the sequence effects were much smaller in magnitude than the scale effects.
To assess the effect of student abilities on completion time, we compared times for an honors section with a sample of the mainstream lab that did the experiments in the same order. On the continuous variation lab, the honors group did both the macro version and the micro versions of the experiment about 10% more slowly than the mainstream classes. On subsequent experiments, the times for both macro and micro work were almost the same. Thus, we wnclude that the aptitude of the student had little measurable effect on completion time. Student Preferences Our study showed a persistent preference for the macro version over the mimo version. For each individual experiment, the difference is not statistically significant. But if all the experiments are combined, the macro version is favored with statistical significance lo < 0.05). (All the differences are in the same direction and accumulate.) I t is interesting and somewhat puzzling to compare the separate parts of the sample. We looked a t gender differences; the antimicro bias is statistically signif~cantonly for the males. It is particularly large for the titration experiment (t = 1.927, p < 0.1). It is not clear why this gender difference should exist. More troubling is that the antimicro attitude was shown strikingly by the students who are ahove the mean CTBS math score but was not statistically significant for those below. The preference of the top of the class was for macro titration (t = 1.914,~ < 0.1). For aU experiments combined, the anti-mim bias was again significant a t the p s 0.05 level a s shown in Table 3. The poll about "favorite experiment" dramatically confinned the result. Students chose macro ex~erimentsover micro experiments by a margin of nearly 3'to 1. The least favorite experiment was overwhelmingly a micro experiment, by the same margin. Microtitration was particularly disliked.
Laboratory work serves many purposes, hut one of them is almost certainly to recruit students into chemistry. According to previous studies (6),college chemistry majors cite the laboratory experience as the second most important reason (after ability in the subject) for choosing chemistry as a maior. For hieh school students. lab is a verv close third, aker ability and the influence of a teacher (16). The additional advantaees of the micro versions h. e- e d .. cost savings) must be balanced against the negative student reaction that seems to occur. It is ~articularlvtroubling when good students show such negative attitudes l e~otentiallvthe future of American because these ~ e o ~are science. We are ndt arguiigthat &dent attitude should be allowed to decide important questions of curriculum, content, and educational rigor. However, to our knowledge, no one has suggested that scale influences the amount students learn. If there is no difference in educational outcome, student preference becomes important by default. Many of the reasons advanced for adopting microscale are economic-not pedagogical. It is troubling that the money saved may come a t the price of making chemistry less attractive.
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Acknowledament This work was supported by NSF grant TPE-8751837, administered throueh thc InstituteforChemical Education of the University oflWisconsin. Literature Cited 1. R~~~.T.MkmClwmisby;KemteeEducatonalCorporation: Kensingon. MD, 1985. 2. Thomaon, S. Chemtmk: M k m s m k E z w r i m n t s for Gemmi Chemistry; Allyn and Bacon: Needham Heights. MA, 1989. 3. Mills, J. L.;Hampton, M. D. MicmscokLaborofary Nnnuoi for Gomml Chpmktry;
Random House: NeuYork, 1988. 4. LaPrade, J. E.:Pieke"w, M. J. ChemEdue. lM, 63,535. 5. Germam, P. J Res. Scl Tchng 1388.25; 689, 6. Gome, 6.;Wyatrach, V . P.; Perkins, R. I. J Chpm. Educ IS%, 62,501 7. Wmdmw Wilson National Fellowship Foundation Mkmchemisfry: Pluledon, NJ,
Chemistry Olympiad Mentor Applications Invited Secondary school chemistry teachers are invited to apply for a position as mentor for the US. National Chemistry Olvmniad nroaam. Duties durine the three-vear term include helnine to ulan and conduct the National Studv Camu United states Air Force ~cademvI'n middune 1992.1993. and 1994. ~ene;allv.& foihibh s&mrstudente held at tf;e~-~ ~-~~~~ thew second mdthird year. mentorsaccompany four Unwd Jtatcs student competitors tu t l w lnternauunal Chrmlatry Olympmd rlChO, Ilunnl: the competition, the mentors will scrvr a* mcmhrrs of the lChO Jury. The 21th 1ChO will hr held July 11-22, 1992, in the United Stater. The U S Natwnal Chrml*tryOlympindis spunsorrd hy the rhcrirnn Chemical Society. Mast students at the Study Camp have completed Advanced Placement Chemistry or the equivalent, therefore inatruetion at the camp is well beyond the level of high school general chemistry courses. The curriculum also includes considerable lahoratoj work. Successful applicants are expected to have a broad background in both theoretical and descriptive chemistry, classroom experience. and should demonstrate involvement with students in special proiects or activities. Ap~licants must be prepared to make a three-year time commitment as outlined ahove. Ail expenses and travel costs, &well as an honorarium, are paid by ACS. Interested individuals should annlv bv reauestine an aonlication fram Denise L. Creech. U.S. National Chemistrv 1f45 ~ i x & n rStreet, h S W..~ a s h i n g t o n ; ~20036 . ~ . Thr desdlm; olympiad Program, American ~h;;n~ca~~oc;rty. for completed npplirations is.January 3, 1992..4pplirants must also arrange t o have three lrttersofrefcrrnrefirwardrd to Dcnisr Creeuhat the ahweaddress.More informmancanbcohtnined by tclephonmgDenise Crecrh at 2024724lfi9. ~
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