Research: Science and Education
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How Do New Teachers Choose New Labs? Stephen DeMeo Department of Curriculum and Teaching, Department of Chemistry, Hunter College of the City University of New York, New York, NY 10021;
[email protected] Most science teachers do not have the time or motivation to develop novel experiments; instead they often use and adapt existing activities from the public domain. This study explores the criteria that new secondary teachers use to choose lab activities within a specific content area. Discussing and critiquing the reasons for choosing a “better” activity from the perspective of the novice could provide current teachers with insight on how quality activities can be chosen. A review of the literature yielded an absence of empirical studies that centered on evaluative processes that teachers use to determine lab activities. Most information on this subject was anecdotal and centered on a variety of science examples that were appropriate on the elementary level. While not supported by research, the type of criteria discussed in the literature was in keeping with the findings of this study (1, 2). Design of the Study A group of high school teachers were given procedures of three chemistry experiments involving the determination of an empirical formula of a compound. Two of the three procedures were classic syntheses used widely in introductory lab courses, the third was less-known but was published in this Journal (3). Science teachers were asked to review and rank the three different experimental procedures according to their own criteria. As part of the study they were asked to provide in writing the following items: • A list of criteria (reasons for making judgments) • Justification for each criterion • A numerical ranking of lab activities • An explanation of ranking of lab activities
This study was conducted with two groups of teachers with each group having about the same number of participants. The first group had 23 teachers while the second group had 25 for a total of 48 participants. Comparison data were collected to determine the level of reproducibility between the two groups. Of the 48 science teachers, there were 29 biologists, 14 chemists, 3 physicists, and 2 geologists. These teachers were all members of a scholarship-based teacher preparation program that leads to certification and a masters degree in science education at the end of two years. At the time of this study, these teachers had been working full-time in public schools for three months and had completed a total of five education courses. Two of the educational courses were science methods courses that were taught by this author. To help nonchemistry teachers to understand the chemistry topic, all participants read procedures and were asked to underline all words they did not understand. The author discussed the meaning of these vocabulary words as well any specific procedures with the teachers. To facilitate additional understanding, teachers were asked to draw, define, or describe a list of specific vocabulary words chosen from the procedures. Most vocabulary included chemistry materials such 1702
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as a crucible, tongs, a boiling tube, and desiccant. Lastly, a discussion was given on the empirical formula concept accompanied by examples and expository notes. While this study involves chemistry experiments and not activities from other sciences, the content of this material is covered in all introductory high school and college courses and should be readily understandable to science majors. All participants had at least one chemistry course as undergraduates. The number of chemistry courses for nonchemists ranged from one to seven, averaging about four. Teachers were given two weeks to complete this study. Because teachers often work cooperatively in actual school settings, participants were allowed to choose to work individually or in small groups. Using outside references such as textbooks were also allowed but had to be mentioned in their writeup. The only restriction involved not discussing this project with colleagues, professors, or other graduate students who previously took this course. The teachers did not perform any of the three experiments. This was done based on the author’s experience that science teachers decide on their activities by first reading them and filtering out those that do not rate well with their internal criteria. Moreover, most teachers do not have the time or a complete set of materials to actually perform experiments within a subject area. The three procedures involved determining the empirical formulas of magnesium oxide,1 copper sulfide,2 and zinc iodide.3 All procedures were modified to facilitate understanding for the teachers. For example, in all procedures reactant and product were described to aid visualization. Other changes included conversion from paragraph to procedural steps, and elimination of references to side reactions, diagrams, theoretical discussions, and postlab questions. These items were omitted to reduce teacher bias when choosing a procedure. Any safety statements were also removed from the three procedures because this was an important criterion I wanted these teachers to consider. Nearly all teachers stated that they did not or could not remember performing any of these syntheses as undergraduates. Finally, no one mentioned that they had any formal experience in the evaluation of laboratory activities in an academic context. These three activities were chosen because all are used on the introductory level, use similar equipment, require about the same class time, and most importantly, involve the combination of elements to form a single compound. This type of combination expresses in the simplest terms, the fundamental idea of chemical change. Findings In order of frequency, Table 1 lists the criteria mentioned and written about by teachers in each group. Some criteria are broken down further for descriptive reasons. As is evident, the top two criteria involve issues of procedural clarity,
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Table 1. Teachers’ Choice of Criteria and How Many Times Each Criterion Was Mentioned per Group Group 1 (N = 23)
Criteria Procedural Issues
Group 2 (N = 25)
Total (N = 48)
34
36
70
•Clear, exact, detailed lab instructions; step-by-step; simple but detailed; easy-to-understand
20
17
37
•Timeliness; fits into one period; fits into time frame; brief
13
12
25
•Less steps; minimal amount of reading
0–
05
05
•Teaches or uses fundamental lab skills
01
01
02
•Procedure incorporates diagrams
0–
01
01
Conceptual Value
28
36
64
•Develops student conceptual understanding of topic or results; effective illustration of concept; conceptually focused
08
09
17
•Accurate, consistent results are produced from procedure; minimizes error
04
08
12
•Appropriate grade level; prior conceptual and skill levels of lab must be appropriate to students’ levels
04
09
13
•Lab activity or procedural steps are explained
06
02
08
•Uses appropriate language or vocabulary; easy to read
04
03
07
•Allows students to recall and apply concepts and skills
01
03
04
•Activity is consistent with state curriculum, meets standards
01
01
02
•Provides pre-lab preparation
0–
01
01
Materials
25
19
44
•Inexpensive supplies
08
07
15
•Uses available equipment; simple equipment that functions properly
08
11
19
•Short material list
02
01
03
•Easy lab clean-up
03
0–
03
•Easy lab preparation and setup
03
0–
03
•Materials are familiar to students
01
0–
01
18
21
39
7
6
13
•Fun, interesting, wow factor
06
03
09
•Relevance; application to society
01
03
04
9
14
23
Safety Issues Motivation
Other Less Common Issues •Stimulates investigation, discovery, further questions, higher-order thinking, research
01
03
04
•Simple calculations; instructions given for calculations
01
02
03
•Quantitative labs preferred
01
02
03
•Visible, obvious product
02
0–
02
•Lab relates to lecture
0–
02
02
•Less supervision required; students work independently
01
01
02
•Can be readily structured for group work
0–
02
02
•Follows scientific method, logical process
01
01
02
•Lab should be written in a structured format
0–
01
01
•Uses many lab skills and concepts
01
0–
01
•Results can be verified by secondary test
01
0–
01
time, and conceptual value. New teachers, who are often preoccupied with management issues, are concerned with activities that fit their time frames and that function properly. Because students usually have no more than one or two class periods to develop an understanding of a specific concept, teachers are more disposed to choose activities that are short and simplistic. Consequently, many activities that are longer to perform but that have educational value are ignored. This is unfortunate. The mention of materials and of safety issues occurred at similar frequencies. Teachers in both groups were acutely aware of the limitation in material and budget needed for www.JCE.DivCHED.org
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hands-on work in a large school system such as those existing today. Faced with using their own personal funds, teachers want to use activities requiring the least expensive and least number of materials. Safety, the fourth criterion, is strongly linked to how students use chemicals, materials, and equipment in the lab. Notably, concern for safety is in tune with new teachers’ concern with controlling student behavior. The last significant criterion teachers noted involved motivation. While not viewed as important in comparison to the other four, a concern for motivation can lead teachers to contextualize their science lessons and imbue science with social significance. The low frequency of this criterion is un-
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fortunate since one way to manage students is to engage them in an activity that relates to their lives, is aesthetically pleasing, or stimulates curiosity. When the teachers applied their criteria to the three experimental procedures to determine which one would be most suitable for chemistry students, a favorite was found in each preference group (Table 2). Teachers in both groups consistently favored the magnesium oxide synthesis, followed by the copper sulfide, and lastly the synthesis of zinc iodide which was emphatically the least preferred of any experiment. Teachers’ reasoning for preferring the magnesium synthesis followed along the lines of the top criteria listed in Table 1. For instance, the magnesium oxide procedure was thought to be more straightforward, simpler, and safer than the other two. While choosing an experiment allowed teachers to apply their criteria and make a value judgment, the manner in which the teachers made their decisions was also noteworthy. Relying mostly on an expository mode of expression, very few teachers fully applied their entire list of criteria to each experiment. Most used fewer than half of their criteria to rule out a competing experiment. Furthermore, very few teachers were systematic in their approach. Only seven of the forty-eight teachers created tables or used point systems to organize or quantify their criteria. Only three teachers used outside reference texts to help them with their decision-making process. Lack of rigor could indicate that certain features of the procedures strongly influenced the decision of these teachers. When one looks at the type of criticisms that the teachers levied against the least favored zinc iodide synthesis, it is clear that teachers perceived procedural details to be an important issue (Table 3). Even though all three syntheses called for heating and demanded fairly long periods of time for cooling, the zinc iodide synthesis was not favored because it was considered too time consuming, complex, and not as safe as the other two. Criticisms of length and complexity might have been due to the zinc iodide activity being described in 18 steps versus the other two syntheses that used 11 steps. As for safety, although some teachers were aware that iodine was an irritant not one participant mentioned that iodine’s degree of irritation is low when in solution, but much higher in gaseous form (4). It should be noted that iodine gas is never made or mentioned in the zinc iodide procedure. For comparison purposes, this author decided to evaluate these three syntheses himself using a table and point system (Table 4). The seven criteria that I used, all of which were mentioned by the new teachers, included safety, the availability of equipment and materials, cost, concept formation, time, motivation, and waste disposal. While I did not provide a weight to each criterion, one important difference between my list and the new teachers’ criteria was the less emphasis I placed on procedural issues such as complexity and the timeliness of the experiment. With experience, I know that many procedures are not etched in stone but can be altered and restructured to save time, get better results, and to promote inquiry. My evaluation of the three different procedures led me to a different conclusion from the one reported by the majority of my teachers. I thought that the zinc iodide synthesis was the best choice and the magnesium oxide experiment the least preferred of the three. Interestingly, this was the opposite order of the teachers’ preference. Our different preferences were due in some instances to my use of the literature to make 1704
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Table 2. Preference for Experiments by Teachers Preference by Number of Teachers
Experiment
First
Second
a
Third
CuS synthesis
b 16 (7,9 )
26 (11,15)
06 (5,1c)
MgO synthesis
21 (12,9)
14 (7,7)
13 (4,9)
ZnI2 synthesis
12 (4,8)
06 (5,1)
30 (14,16)
a
The numbers in parenthese are the number of teachers in group 1, followed by the number of teachers from group 2. bOne teacher rated the CuS and MgO experiments a first place tie. cOne teacher rated MgO and ZnI2 experiments a second place tie.
Table 3. Top Three Criticisms That Teachers Levied against the Zinc Iodide Procedure Criticisms
Total
Group 1
2
Too long; too many steps; procedure is too detailed; repetitious steps; numerous heatings; time consuming; many measurements; more than one period is needed
61
34
27
Confusing; complex; too involved; complicated; academic level not appropriate
28
9
19
Not safe; iodine is corrosive; causes burns; perhaps cancer causing; safety procedures not clear; too risky; toxic fumes; skin irritant; can burn self
22
11
11
judgments about safety issues, cost, and the prevalence of side reactions. Additionally, what really separated the zinc iodide synthesis from the other two involved its potential for allowing students to understand the concept in a motivating manner. The zinc iodide reaction involved vivid color changes that were clearly observable while the other syntheses used covered crucibles and thus blocked the visibility of any chemical transformations from taking place. Seeing quantified reactants actually undergo chemical change seemed a great impetus to ask questions about how substances combine and to appreciate the resultant formula and chemical equation. Conclusion This study revealed that new science teachers used many sound criteria for deciding which lab activity was the best to include into their curriculum. While these criteria are useful to apply, new teachers should consider the importance of student motivation and place it on par with the other top criteria that were mentioned. Motivating students through inquiry-based, socially relevant, or aesthetically pleasing activities can help academically challenged students who are questioning the value of attending an often mandatory science course. New teachers, as they gain experience and improve their management skills, should also realize that procedural concerns do not have to be so narrowly focused when evaluating activities; procedures in many cases can be tailored to meet the needs of their students. Another implication that is relevant to graduate-level instructors who teach science methods to new teachers is to include lab evaluation in their curriculum. New teachers should be involved in a discussion of criteria, the systemization of the evaluation process, reference texts that address
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Table 4. Author’s Evaluation of the Three Experimental Procedures Criterion
Magnesium Oxide Synthesis
Copper Sulfide Synthesis
Zinc Iodide Synthesis
Safety
1. Burning of Mg produces bright light, but is shielded by crucible lid. 2. Crucibles can break during heating.
1. During heating, H2S is liberated. Choking on these fumes can occur if reaction is not well ventilated. 2. Crucibles can break during heating.
1. Iodine can stain the hands and objects in the lab. (Iodine stains can be removed with a solution of sodium thiosulfate.) 2. Iodine is kept in soln. during the reaction; it is not released as a gas.
Value = 2
Value = 1
Value = 2
Availability of equipment and materials
All readily available and uses common equipment.
All readily available and uses common equipment.
All readily available and uses common equipment.
Value = 3
Value = 3
Value = 3
Cost
1. Crucibles are costly ($2–4 ea.). 1. Crucibles are costly ($2–4 ea.). 1. All substances and materials are 2. Only one reactant is purchased 2. Substances are inexpensive. inexpensive. and it is inexpensive. Value = 2
Value = 2
Value = 3
Concept formation
1. Incomplete combustion can produce erroneous empirical formula. 2. Students often have misconceptions involving colorless gases. 3. Crucibles can crack and break invalidating results.
1. More than one empirical formula can be formed (i.e., Cu9S5) 2. Crucibles can crack and break invalidating results.
1. Only ZnI2 is formed, but is susceptible to hydration if not sealed. 2. Use of large boiling tubes prevents spills.
Value = 1
Value = 2
Value = 3
Time
1. One trial per 1.5 h. 2. Involves heating and cooling.
1. One trial per 1.5 h. 2. Involves heating and cooling.
1. One trial per 1.5 h. 2. Involves heating and cooling.
Value = 2
Value = 2
Value = 2
Motivation
1. Reaction is not observable (covered by crucible lid). 2. The change from the initial color of reactants (metallic) to the color of the product (white) is slightly interesting to observe.
1. Reaction is not observable (covered by crucible lid). 2. The change from the initial color of reactants (copper and yellow) to the color of the product (black) is interesting to observe.
1. Reaction is observable. 2. Warming of the test tube during reaction is felt. 3. The change from the initial color of reactants (gray and dark purple) to the color of the product (white) is interesting to observe.
Value = 1
Value = 2
Value = 3
Waste disposal
1. Solid product must not be disposed of through sewer system. 2. Product must be collected separately as non-toxic waste.
1. Solid product must not be disposed of through sewer system. 2. Product must be collected separately as non-toxic waste.
1. Product dissolves in water. Product can be diluted and disposed through sewer system. 2. Excess zinc can be recycled.
Value = 2
Value = 2
Value = 3
Total (out of 21 points)
13
14
19
safety issues, cost of materials, and background knowledge on the concept and procedure being taught. If one considers that many teachers will only use one activity to demonstrate a concept, it is critical that teachers choose the best lab that will allow students to construct understanding.
Investigating the Fundamentals of Chemical Change; 2000. Unpublished manuscript used at Hunter College of the City University of New York. W
Supplemental Material
The procedures to determine the empirical formulas of MgO, CuS, and ZnI2 are available in this issue of JCE Online.
Notes 1. The empirical formula of magnesium oxide was determined via the reaction of magnesium metal with excess oxygen. Richards, L.; McGee, T. H. An Introduction to Experimental Chemistry, 5th ed.; Avery Publishing Group: Garden City, NY, 1994. 2. The empirical formula of copper sulfide was determined via the reaction of copper metal and sulfur. King, G. W. General chemistry I laboratory manual; 1989. Unpublished manuscript used at Barnard College of Columbia University. 3. The empirical formula of zinc iodide was determined via the reaction of zinc and iodine. DeMeo, S. Cornerstone Chemistry: www.JCE.DivCHED.org
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Literature Cited 1. Feldkamp, P. B.; Rillero, P.; Brownstein, E.Teaching K-8 1994, Feb, 52–54. 2. Feldkampm, P. B.; Rillero, P.; Brownstein, E. Science and Children 1994, Mar, 16–19. 3. DeMeo, S. J. Chem. Educ. 1995, 72, 836. 4. Sittig, M.; Pohanish, R. Sittig’s Handbook of Toxic and Hazardous Chemicals and Carcinogens, Vol. 1, 4th ed.; William Andrews: New York, 2002.
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