Research: Science and Education edited by
Chemical Education Research
Diane M. Bunce
A Procedural Problem in Laboratory Teaching: Experiment and Explain, or Vice-Versa?
The Catholic University of America Washington, D.C. 20064
Pasl A. Jalil Department of Chemistry, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia, and Institute of Academic Development and Training (IADAT), Khobar 31952, Saudi Arabia;
[email protected] One could easily claim that no skillful scientist or physician acquired his or her skill solely through an extensive study of written materials, or even through the observation of other skilled individuals. University laboratories, or some school laboratories, often provide the first connection between theory and practice. A diligent student who has learned chemistry principles in class should also do laboratory work to know how to select theories for efficient and effective use (1, 2). According to Perry’s model of intellectual development, first-year college students are usually dualistic in thinking: that is, they see the world in dualistic fashion involving the opposites of right–wrong, good–bad, and think that truth is absolute, and uncertainty can only be temporary (3). This thinking changes with experience to a more complicated, contextual view of reality (relativism) (4). Unfortunately, most university laboratories provide the opportunity to strengthen the dualist perspectives of students by specifying exactly what data they are supposed to collect to verify the truth that has already been explained and discussed by the instructor (4). This kind of conventional teaching leaves no room for hypotheses, trials, errors, or individual responsibility, and precludes the student’s involvement in decision-making processes, which are so important in scientific research and development. To overcome such problems, many methods have been developed and implemented. For example, in a guided inquiry approach, students may design the experiment through teacher-led discussions and certain practical efforts (5–10). Cooperative and active learning (11–16) and problem-solving teaching (17) are important methods for intellectual development and enhancing critical thinking among students. Generally, instructors explain or demonstrate the experiment to students before they are allowed to conduct it, and often even the expected results are discussed (4). Strictly speaking, there has been no explicit answer to the question of whether the instructor should explain the experiment in a given laboratory before students do the experiment or whether the experiment should precede the explanation and the discussion. This work describes two approaches, I and II, to teaching the laboratory segment of the first freshman chemistry course at our institution. Approach I used the model of explaining and demonstrating each experiment first before the students participated. The expected results were also discussed. In Approach II the students performed the experiment themselves with minimal assistance before any explanation or discussion. Students’ perceptions of the effectiveness of each approach were measured by a questionnaire;
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the results of the questionnaire were compared with the performance of students on key quiz questions. Experimental Methodology The chemistry department Chem 101 laboratory manual was used in this study without any changes. The manual consists of explicit instructions enabling students to carry out an experiment after it is explained or demonstrated. All the equipment needed was prepared for students and ready at their lab benches. Students conducted 12 experiments in each semester of the 14 semesters studied. These experiments are presented in chronological order in List 1. In this study, we compared two basic approaches to laboratory teaching: explain and experiment (Approach I) and experiment and explain (Approach II). For Approach I, each experiment was explained and demonstrated to the students prior to their participation. The expected results were also discussed. At the end of each explanation, to ensure understanding, questions were asked such as: “Is everything clear?” “Who has more questions?” “If you do not understand anything do not hesitate to ask. Go ahead and do the experiment”.
List 1. Topics of Laboratory Experiments for the First Semester of Chemistry 101 1. Significant figures 2. Density 3. Paper chromatography and mass spectroscopy 4. Gas constant 5. Molecular weight of a volatile liquid (Dumas method) 6. Heats of reaction (coffee-cup calorimeter) 7. Analysis of a heterogeneous mixture (NH4Cl, NaCl, SiO2) 8. Percentage of barium chloride hydrate in a heterogeneous mixture 9. Qualitative analysis of anions 10. Qualitative analysis of cations 11. Melting point and boiling point 12. Freezing point depression
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In Approach II, the students started the experiment without any explanation from the teacher. However, the teacher identified experimental equipment (e.g., glassware names, centrifuge machine, litmus paper, etc.) when necessary. Then students began the experiment, following the steps of the experimental procedure using the same laboratory manual. In this approach, each student interpreted and performed the steps in the experiment in his or her own way. However, students were monitored while performing the experiment to ensure that they were going in the right direction. Any student who was obviously struggling was given assistance. The instructor could intervene by asking questions such as: “Do you know how can you manage this?” “What if you do this?” “Is it better to do it this way or that way?” Questions such as “Why you are doing this?” were not asked, as they might
List 2. Survey Statements Regarding Students’ Perceptions towards Their Lab Experiences
Surveying Procedure The survey was conducted over two years in Chem 101 lab sessions, yielding responses from a total of 241 students (in 14 sections) who were taking their first chemistry laboratory. All of them were the author’s students. The period of study extended from the fall semester of 1999 to the spring semester of 2001. At the end of each semester the students were asked to complete a questionnaire probing students’ perceptions regarding these four aspects of laboratory work: • Understanding the experiment
Understanding A. I understand better if I do the experiment first and then it is explained by the instructor. B. I understand better if the experiment is explained first by the instructor and then I do it after that. C. No clear difference.
Enjoyment
• Enjoyment in doing the experiment • Achievement in conducting the experiment • Difficulty of doing the experiments
Each of these topics included three self-explanatory statements, except the topic on difficulty, which had four. Students were asked to choose one statement for each topic that best described their own position regarding that topic. See List 2 for the survey instrument.
A. Overall, I enjoy the lab more if I do the experiment before an explanation.
Results and Discussion
B. Overall, I enjoy the lab more if I do the experiment after an explanation.
The survey results were tabulated so that student responses (choosing statement A, B, C, or D) for each topic could be expressed as a percentage. Table 1 shows the results of the questionnaire over 14 sections concerning students’ preferences for the method of teaching experiments in the laboratories. An analysis of variance (ANOVA) shows that there is a significant difference in the two approaches for each variable; Table 2 provides those results. This significant difference is confirmed when t-tests are applied between the two approaches for each variable (see Table 3). As can be seen from Table 1, 54% of the students indicated that they understood better if they did the experiment first and then had explanation and discussion after that. However, only 32% of the students felt they understood better if the experiment was explained first. A total of 14% of the students selected statement C, indicating that they perceived no clear difference as far as understanding was concerned. There are many factors that could explain these results. If we consider Bloom’s levels of learning (18), it is clear why most of the students prefer to do the experiment before an explanation. Simply, it is the natural process of learning to start with observation, which is the first step in Bloom’s taxonomy—knowledge (18). When the experiment is explained before doing it, the instructor is addressing higher levels of learning (e.g., application and analysis), without addressing the first level, knowledge, in a proper way. This means that
C. No clear difference.
Achievement A. I feel that I achieve something if I do the experiment before an explanation. B. I feel that I achieve something if I do the experiment after an explanation. C. I feel my achievement is the same in both cases.
Difficulty A. It is more difficult to do the experiment before it is explained. B. It is more difficult to do the experiment after it is explained. C. In the beginning, it was more difficult for me to do an experiment before it was explained, but now it is normal or nearly normal to me. D. Doing the experiment before or after the explanation has the same difficulty.
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elicit defensive behavior rather than creative thought. No student was allowed to leave the laboratory unless he or she had demonstrated the experiment correctly. For each semester, and for each section, students started with Approach I, in which 6 (±2) experiments (out of the 12 experiments in the semester) were conducted in the conventional format; the remaining experiments were then conducted using Approach II. In essence, all students in each section experienced both approaches throughout the study.
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Table 1. Survey Results Comparing Student Agreement by Laboratory Section Lab Sections Studied (N values in parentheses; values indicating agreement with the statements are in %) Survey Topics and Statements
Avg ±σ
1 (12)
2 (16)
3 (14)
4 (19)
5 (17)
6 (20)
7 (16)
8 (16)
9 (16)
10 (19)
11 (17)
12 (17)
13 (19)
14 (23)
MMA. Experiment first
54± 13
75
69
64
63
59
56
56
56
56
53
53
51
33
26
MMB. Explanation first
32± 11
25
18
22
21
29
24
31
38
38
31
29
26
53
52
MMC. No difference
14±60
00
13
14
16
12
20
13
06
06
16
18
23
14
22
MMA. Experiment first
54± 12
83
63
57
53
65
50
75
56
56
42
47
41
47
39
MMB. Explanation first
32± 13
09
24
29
36
17
25
13
25
25
47
35
59
37
48
MMC. No difference
16±40
08
13
14
11
18
25
12
19
19
11
18
18
16
13
MMA. Experiment first
78 ± 8
92
88
93
84
76
75
75
81
63
79
82
70
73
70
MMB. Explanation first
12 ± 4
08
00
07
11
18
15
19
13
12
11
12
12
01
13
MMC. No difference
10 ± 7
00
12
00
05
06
10
06
06
25
10
06
18
16
17
MMA. Experiment first
18± 10
08
06
07
16
12
20
13
12
25
21
06
29
32
35
MMB. Explanation first
0
00
00
00
00
00
00
00
00
00
00
00
00
05
00
MMC. No difference
76± 11
92
94
86
79
88
70
81
88
75
68
82
64
58
61
MMD. Same difficulty
5±4
00
00
07
05
00
10
06
00
00
11
12
07
05
04
Understanding
Enjoyment
Achievement
Difficulty
some students may not even know what the instructor is talking about; some students may misunderstand and misconceptions can take root. Using Approach II, students saw the results of an experiment and then discussed the phenomena related to that experiment. This promotes better visualization of the underlying concepts of that experiment. In addition, students carried out the experiments independently, deliberating and arriving at conclusions with minimal guidance from the instructor. As mentioned in the procedure section, students were not given direct answers. This may facilitate critical thinking, encourage students to use knowledge they already have acquired, and help them identify and seek necessary additional information. Note that, while in Approach I, students acted as receivers of information and demonstrated that they are able, more or less, to repeat the experiment, in Approach II the students had to think more independently, they had to judge many things and interpret the manual correctly. This enhances the basic elements of active learning among students. When students discover answers on their own, retention improves and deeper understanding develops (19–20). Further investigation of the data in Table 1 reveals that enjoying doing the experiment first—Approach II—is correlated with understanding, r = 0.47. (See Understanding, statement A and Enjoyment, statement A in Table 1). This
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Table 2. Analysis of Variance Results by Survey Topic Variable
F Values
P > F Values
Understanding
042.66
0.0001
Enjoyment
041.29
0.0001
Achievement
311.20
0.0001
Difficulty
257.88
0.0001
Table 3. Comparison of Two Teaching Approaches Using t-Test of Difference by Variable (Survey Topic) Variable
t-Test Values
P Values
Understanding, A and B*
3.21
< 0.01
Enjoyment, A and B*
3.21
< 0.01
Achievement, A and B*
9.65
< 0.01
Difficulty, A and B*
3.11
< 0.01
*For statements A and B, see List 2.
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coincides with findings in the literature (21–22). Hence, enjoyment during the laboratory period may have contributed to better understanding of the experiments. This could have the effect of making the students less bored by the experiments. Many students, if not most of them, are willing to obtain the data and then leave lab as quickly as possible. Creating enjoyment could be one way to forestall this “takethe-data-and-run” situation. This allows more time for students to think and ask questions that subsequently contribute to improved understanding of the concepts underlying the lab exercise. A significant majority of students reported on the survey that they feel a sense of achievement when they undertake the experiments first, without prior explanation. (See Table 1, Achievement, statements A and B). This holds even for students indicating that their understanding decreased from doing the experiment first (Table 1, sections 13 and 14). Using Approach II presents a salient and anticipated problem: the difficulty of carrying out the experiment without an explanation. Responding to statements about the difficulty of doing the lab work, 76% of the students chose statement C, agreeing that they had difficulty initially in following this approach, and then it became normal or nearly normal to them. When students first began experiments without prior explanation their difficulties were noticeable; there was a very clear difference between the initial and the final stages of doing the experiment first by themselves. Note that the lab manual was not designed to be used independently, which increased the difficulty of Approach II. In many cases, the lab manual states “your instructor will demonstrate this to you”. When the students then asked to be shown, they were usually told “You are the instructor”. This kind of answer seemed to be helpful to the students in that it pushed them to act more independently. Again, in all of the sections studied, the students seemed to gain independence after doing the experiment first (see Table 1, Difficulty statement c). This might be attributed to Approach II. Although the survey results show that students in section 13 and 14 perceived that they understood experiments better with explanation first (see Table 1: Understanding statement A, sections 13 and 14), the survey also indicates that using Approach II increased the independence of these students (see Table 1, Difficulty statement C, sections 13 and 14 ). Students benefit from learning with Approach II, in part because they can understand and visualize better what the instructor is talking about since they come to the discussion having experimented with the chemistry concepts. This reduces the probability of students developing misconceptions compared to the conventional method. In known–unknown experiments, the discussion followed the known part; students could answer most of the expected questions easily following the unknown part. This was not true using Approach I. The students were able to finish the experiment following Approach II in the specified lab period of 4 hours. However, Approach II requires roughly one hour more than Approach I did. Deeper investigation of the sections in Table 1 shows a correlation (r = 0.47) between the sense of achievement after doing the experiment (Achievement statement A) and overcoming the difficulty of doing the experiment (Difficulty statement C as shown in Table 1). This sense of achievement 162
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Table 4. Distribution of Students Preferring Experimentation First, by Quiz Performance Quiz Grade Categories a
Number of Students in Category
Students Preferring To Experiment First
ⱖ a ⫹ 1.5σ
20
20
(100%)b
ⱖa⫹σ
48
43
0(90%)b
ⱕa⫺σ
50
14
0(28%)b
ⱕ a ⫺ 1.5σ
35
6
0(17%)b
a Categories based on an average of the quiz grades, a, plus or minus the standard deviation, σ. b The percentage of students preferring experimentation first whose quiz scores put them in this category.
may derive from students’ pride in overcoming the difficulty of the experiment with minimal help, which enhances selfconfidence. Since this study was done with first-year students, it is very important to note that most first-year students are dualistic thinkers (23). By doing the experiment independently, students must think of what they are doing, especially since they do not know the expected result. They have to think more creatively; in fact, students may do the experiments differently from the way the experiment is described in the lab manual. Students noticed the differences: several times students asked why some students’ procedures differed. Typically the reply was that students could do whatever they thought appropriate; they would also be told that there is more than one way of solving a problem. This should guide students from a dualistic state of thinking to a more complex one. Lab instructors should try to lead students from simplistic, right–wrong patterns of thinking to a more complex, contextual view of reality. Instructors can effectively act as guides or consultants rather than sources of authority with absolute knowledge to best educate students. Correlating Students’ Performance and Preferences More high-performing students prefer to do experiments before explanation than low-performing students. Table 4 shows the distribution of the students who prefer to do the experiment before an explanation. Based on their lab quiz grades students were grouped in one of four categories. Although all of the quizzes were “open book”, the quiz questions required a certain level of intellectual skill and were not straightforward. The quizzes were given after carrying out the experiment and discussing the results. Unexpectedly, 100% of the high-performing students (defined as those who have grades ≥ a + 1.5σ, where a is the grade average of the quizzes for each class and σ is the standard deviation of the grades) preferred to do the experiments before an explanation. Conversely, only 17% of students whose grades were ≤ a – 1.5σ preferred to do the experiment before explanation. So, could we use the answer on Understanding statement A, List 2, as an indicator of class performance? Much more data need to be collected, perhaps internationally, to produce valid answers to this question.
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Conclusion In this work we presented the results of our experiment of two approaches (I explain, then experiment; II experiment, then explain) of teaching laboratory. As the data reveal, Approach II better matches the majority of students’ preferences regarding their understanding, enjoyment, and positive feeling of certain achievement during doing the experiments compared to Approach I. Although the students face some difficulty initially using Approach II, that difficulty lessens for most of the students as they continue to conduct lab work before explanation. Opportunities to experiment and develop self-reliance and independence are essential to learning to solve problems, in both scientific research and students’ lives outside of class and lab. Acknowledgments The assistance of the Chem 101 students at King Fahd University of Petroleum and Minerals (KFUPM) who participated in this study is gratefully acknowledged. In addition, I acknowledge and thank the following individuals for their comments, suggestions, and encouragement: S. J. Piccinin, director of the Center for University Teaching, University of Ottawa, Ottawa, Canada; G. Owmeiren, Chemistry Department, KFUPM; M. Fettohi, coordinator of Chem 101, KFUPM; and B. Yashau, Mathematics Department, KFUPM. Literature Cited 1. Larkin, J. Am. J. Phys. 1981; 49, 534–541. 2. Huddle P. A.; White M. D.; Rogers F. J. Chem. Educ. 2000, 77, 104–110 and references therein. 3. Finster D. C. J. Chem. Educ. 1989, 66, 659–661 and references therein. 4. Finster D. C. J. Chem. Educ. 1991, 68, 752–756. 5. Hanson D.; Wolfskill T. J. Chem. Educ. 2000, 77, 120–130.
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6. Ricci, R. W.; Ditzler, M. A. J. Chem. Educ. 1991, 68, 228– 231. 7. Deckert, A. A.; Nestor, L. P.; Dilullo, D. J. Chem. Educ. 1998, 75, 860–863. 8. Crowley, L. A. In Proceedings of the Frontiers in Education 1998 Conference, Tempe, Arizona, Nov 1998; Stipes Publishing: Champaign, IL, 1998; p 379. 9. Palincsar, A. S.; Magnusson, S. J.; Marano, N.; Ford, D.; Danielle, B. N. Teach. Teach. Educ. 1998, 14, 5–19. 10. Tien, L. T.; Stacy, A. M. In Proceedings of the Annual Meeting of the American Educational Research Association, New York, NY, Apr 1996; American Educational Research Association: Washington, DC, 1996; pp 8–12. 11. Johnson, D. W.; Johnson, R. T.; Smith, K. A. Active Learning: Cooperation in the College Classroom; Interaction Book Co.: Edina, MN, 1991. 12. Robinson W. R. J. Chem. Educ. 1997, 74, 622. 13. Nurrenbern, S. C.; Robinson, W. R. J. Chem. Educ. 1997, 74, 623. 14. Yager, S.; Johnson, D.; Johnson, R. J. Educ. Psychol. 1985, 77, 60–66. 15. Reis, J. C. In Proceedings of the Frontiers in Education 1998 Conference, Tempe, Arizona, Nov 1998; Stipes Publishing: Champaign, IL, 1998; pp 635–640. 16. Davis, W. K.; Nairn, R.; Paine, M. E.; Anderson, R. M.; Oh, M. S. Acad. Med. 1992, 67, 470–474. 17. Gallet, C. J. Chem. Educ. 1998, 75, 72–77. 18. Bloom, B. S. Taxonomy of Educational Objectives: The Classification of Educational Goals: Handbook I, Cognitive Domain, 1st ed.; Longmans, Green: New York, 1956. 19. Miller, T. L. J. Chem. Educ. 1993, 70, 187–189. 20. Bodner, C. M. J. Chem. Educ. 1986, 63, 873–878. 21. Christianson, S. Psychol. Bull. 1992, 112, 284–309. 22. Jacobs, W. J.; Nadel, L. Psychol. Rev. 1985, 92, 512–531. 23. Perry, W. G. Forms of Intellectual and Ethical Development in the College Years: A Scheme; Holt, Rinehart, & Winston: New York, 1970.
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