Extensiveness and perceptions of lecture demonstrations in the high school chemistry classroom

Abstract

While lecture demonstrations have been conducted in chemistry classrooms for hundreds of years, little research exists to document the frequency with which such demonstrations are employed or their effect on learners' motivation and performance. A mixed-methods research study was performed, using quantitative and qualitative survey data, along with qualitative data from follow-up interviews and structured email correspondence. Fifty-two randomly selected chemistry teachers completed a survey regarding their present and projected use of classroom demonstrations. Twelve of the survey participants provided elaboration in the form of an extended questionnaire. Data indicate that all except one of the survey participants currently employ lecture demonstrations, and all anticipate performing the same number of, or more, demonstrations in their future instruction. Extended questionnaire and survey data reveal that the participating chemistry teachers perceive substantial positive effects on students’ performance on classroom assignments and a lesser, though still positive, effect, on learners' motivation. No correlations were observed between the number of lecture demonstrations performed and educators' years of experience teaching chemistry, previous exposure to demonstrations, or undergraduate degrees earned.

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Introduction

Observations of high school chemistry teachers' practices, and other anecdotal evidence, suggest that the use of classroom lecture demonstrations is widespread. Chemical suppliers offer prepackaged kits, and even accredited courses, to encourage and support the inclusion of such demonstrations in educators' daily practice (Flinn Scientific Inc., 2011). Chemistry and physics teachers at a number of schools employ attractive demonstrations to advertise course offerings and increase enrolment (Inver Hills Community College, 2011), with some institutions employing “full-time resource [staff] to develop, archive, and prepare lecture demonstrations” (Youngstown State University, 2011). Whether inclusion of classroom demonstrations advances students' interest and understanding remains unverified. The absence of published literature regarding the extensiveness and perceived effectiveness of lecture demonstrations indicates an opportunity for research to benefit current and future chemistry teachers and science education programs.

Definition of lecture demonstration

Lecture demonstrations have been conducted in science classrooms for at least three centuries. Taylor (1988) traces education via demonstrations of scientific principles to the late seventeenth century, with eminent figures such as Robert Hooke appointed as early as 1662 to act as demonstrators for Fellows of the Royal Society. Taylor further states that “public demonstrations as part of a course of instruction” (which are presumably the equivalent of modern lecture demonstrations) began in 1694. There are certainly abundant references to classroom demonstrations illustrating specific scientific principles in academic literature of the intervening centuries. Michael Faraday (1904) used demonstrable phenomena as the basis of his famous 1827 and 1860–61 lecture series; more recently, texts such as those of Shakhashiri (1983, 1985, 1989, 1992, 2011), Sprott (2006), and Shmaefsky (2004) feature hundreds of demonstrations for high school and college students of chemistry and physics.

Kauffman (1996) cites Jensen (1991) in claiming that early chemistry instruction was “solely by demonstration”, although Kauffman's subsequent reference to the introduction of laboratory experience to students' education suggests that said demonstrations were a part of lecture-based courses used in lieu of learners' laboratory work and not the sole means of introducing concepts. Regardless, Kauffman presents a detailed history of the lecture demonstration, including what he terms a “golden age” of scientific demonstrations presented for students, but also for members of the public. Perhaps tellingly, one of the educators featured in Kauffman's article, Sir Humphry Davy, found that despite the consistent appeal of his demonstration-laden lectures, the society gentlemen in attendance were not motivated to further pursue scientific endeavors. Davy's observation is in contrast to a statement by Taylor: “it [lecture demonstration] seems to work with all age groups and is a great way of inculcating a sense of excitement about science”. The apparent contradiction was part of the focus of this research study.

Taylor defines a demonstration as an “illustration of a point in a lecture or lesson by means of something other than conventional visual-aid apparatus”. Presumably, laboratory investigations performed by students, although nominally covered under the aforementioned description, would not be considered “demonstrations”. We shall amend Taylor's definition to explicitly state that a “demonstration” should be instructor-led, with students observing results; in some instances, the demonstration might follow learners' predictions of outcomes—active mental participation—in order to introduce and address discrepant events. The resulting characterization appears to be a standard interpretation of the meaning of “lecture demonstration”. Tai et al. (2005) appear to make a similar distinction between demonstrations and “laboratory experiences”, although no explicit definition of either is presented.

Previous research

The abundance of information related to performing classroom science demonstrations is an unsubtle suggestion that educators who do not include attention-grabbing performances as part of their normal teaching are somehow remiss. Most of the authors cited in this article presume that the use of science demonstrations is—or at least should be—practically universal, with promoters emphasizing the “charm” (Ramette, 1980) or “entertaining distraction” (Shmaefsky, 2005) afforded by lecture demonstrations. Less convinced are Roadruck (1993) and Swanson (2010), who posit several credible reasons why some educators might choose not to include demonstrations in their instruction. Neither, however, presents any research data to validate their rationales.

Meyer et al. (2003) also suggest some reasons for educators not to employ lecture demonstrations, but offer what amounts to a straw-man argument apparently designed to favor their use. For example, their assertion that “many new teachers… have not been exposed extensively to the value and pedagogy of demonstrations and are uncomfortable with the thought of conducting them in class” implies that more experienced educators would most certainly incorporate lecture demonstrations—that unwillingness is merely due to teachers' inexperience, as the “value” of demonstrations is self-evident. Meyer et al. (2003) at the same time lament that “[un]fortunately, quantitative education research does little to promote the use of demonstrations”, and are apparently unwilling to recognize that a lack of support for their assumption may indicate a flawed premise. Indeed, Tai et al. (2005) found no correlation between frequency of demonstrations in college students' high school chemistry classes and their grades in introductory chemistry courses, while Tai and Sadler (2007) observed a negative correlation.

Results from a study presented by Manaf and Subramaniam (2004) purport to show gains in student learning and interest resulting from the inclusion of lecture demonstrations in chemistry instruction, but the study was (by its authors' admission) not well controlled and its applicability is suspect. A more plausible study published by House (2000) correlates data obtained by interviewing a large sample of 13-year-old students in Hong Kong with their performance on the 1999 TIMSS (Trends in International Mathematics and Science Study) exam. In the study, House determined that various instructional strategies, including classroom demonstrations, produced a significant effect on students' learning. In particular, multivariate regression analysis suggests that demonstrations by themselves (i.e., in the absence of other beneficial instructional techniques) account for a small percentage of the variance in the exam scores. The House study does not, however, provide any detail regarding the definition of “demonstration” apart from its characterization as an activity performed by the teacher.

Crouch et al. (2004) state that learners must be actively engaged in order to realize gains in conceptual understanding; although the research of Buncick et al. (2001) indicated increased student engagement, measures of performance and motivation (attitudinal) gains were inconclusive. Pierce and Pierce (2007) describe favorable learning outcomes arising from the use of demonstration assessments, wherein significant learning gains were produced on assessment items directly related to demonstrations as long as the demonstrations were unconnected to laboratory topics. Interestingly, midterm and final exam scores indicated that the Pierce and Pierce's treatment group—students who completed written post-demonstration assessments—did not perform better than the control group, and, on two of the three post-treatment exams, performed significantly worse.

Silberman (1983) discusses a deleterious effect of chemistry demonstrations, highlighting students' explanations of a common demonstration that illustrate their persistent misconceptions and apparent disinterest in determining the real explanation for observed phenomena. These findings are not the result of formal research, but Silberman's recommendations (“do [i.e., perform]… better demonstrations and… question students' understanding in order to improve observational and interpretive skills”) are similar to those of later investigators such as Shmaefsky (2005) and Baddock and Bucat (2008). Clermont et al. (1993, 1994) have perhaps provided an explanation for the negative findings of Tai and Sadler (2007), suggesting that improperly-performed demonstrations may lead to the introduction and entrenchment of misconceptions; a particularly attractive demonstration, explained incorrectly, may be harmful to students' understanding.

Purpose of the study

Published articles regarding lecture demonstrations address the putative reasons for their inclusion in chemistry pedagogy. The absence of a solid research basis for claims of increased student learning and motivation, however, calls those claims into question. Research that might provide evidence to support or refute such contentions begins with the determination of why, and how often, classroom demonstrations are used by high school chemistry teachers.

One cannot reasonably determine the effectiveness of classroom demonstrations without a sense of their prevalence; the literature, however, is silent with respect to the extent to which lecture demonstrations are employed in high school and college classes. The research described herein, then, attempts to articulate the frequency and methodology of use, as well as the intended purposes and means of assessment, of demonstrations in high school chemistry classrooms. While measurement of gains produced by the use of lecture demonstrations may be the focus of further research, a sense of the perceived benefits arising from their inclusion in classroom instruction should provide an effective starting point for such investigations.

It may be that educators have chosen to include lecture demonstrations in, or exclude demonstrations from, their repertoire based on their own experiences—as students or as teachers—in the classroom. Data from the research study elucidate some of the reasons why teachers employ lecture demonstrations. In particular, educators were asked about their experience with demonstrations; concepts that are effectively taught using demonstrations; their familiarity with published research related to science demonstrations; and how—if at all—they expect to alter their use of lecture demonstrations in their classrooms.

Methodology

Selection of survey participants

The sample frame for the investigation consisted of high school chemistry teachers working in the United States. A list of three hundred potential survey participants was populated by first choosing the state from which a high school would be selected, using a random number generator and the most recent national census data to ensure that the chance of a state's selection was proportional to its population. Once a state had been chosen, a high school was randomly selected from that state's high schools listed in a comprehensive national database (accessible online at http://schooltree.org/high/). Following the identification of the high school, each chemistry teacher at the institution was given an equal chance of selection, either by random choice from a list published on the school's Web site, or—when insufficient data were available online—by asking the switchboard operator at the school to randomly choose an individual from the available pool of chemistry teachers. Eighty-eight chemistry teachers, representing public, private secular, and private religious institutions located in urban, suburban, and rural settings, were contacted during the spring semester of 2011. Fifty-two of those contacted returned completed surveys—a response rate of 59.1 percent. Approval for the study was granted by the University of Nebraska-Lincoln Institutional Review Board, project number 20100510787 EX.

Survey instrument

The survey consisted of two major parts: a selected-response section—in which options were presented in the form of a balanced five-point Likert scale—and an open-response section. The selected-response section was further divided into two segments consisting of four items each; the two segments addressed perceived effects of classroom lecture demonstrations on students' performance and motivation, respectively. For each of the eight selected-response items, scores of 1 and 2 represented strongly and slightly negative perceived effects, respectively, while scores of 4 and 5 indicated, respectively, slightly and strongly positive perceived effects. A score of 3 represented no perceived effect.

The open-response section, consisting of six items, requested information regarding chemistry teachers' prior exposure to lecture demonstrations, the frequency with which the teachers now (and plan to) employ such demonstrations, educators' years of teaching experience, and their educational background.

Extended questionnaire

An interview with each contributor, although nominally preferable for maximizing validity of responses, is an unrealistic prospect. Consequently, a subset consisting of twelve high school chemistry teachers—chosen to maximize the variety of teaching experience and expressed opinions regarding lecture demonstrations—was selected from volunteer participants in the first-round survey. An extended questionnaire was completed by the twelve volunteers either through telephone interviews or via structured email correspondence. The extended questionnaire addressed the teachers' definitions of, and practices regarding classroom lecture demonstrations, concepts addressed via demonstration, the role of teachers and students in the performance of demonstrations, and familiarity with existing research regarding lecture demonstrations.

The medium by which extended questionnaires were completed—via electronic mail or telephone—was determined by mutual agreement of the researcher and survey participants. The same set of initial questions was asked of, and the informed consent statement read or sent to, each of the three telephone interview subjects and nine email correspondents. Once a participant had agreed to the consent statement and completed the initial telephone interview or email correspondence, follow-up questions were presented to those subjects whose responses invited elaborations or clarifications. The combination of the two communications in each case provided the complete set of responses sought.

Participants' background and experience

Subjects participating in interviews or structured email correspondence reported chemistry teaching experience ranging from one to thirty-two years. The mean years of chemistry teaching experience exhibited by teachers in the interview and correspondence group (x̄ = 12.8, s = 9.81, n = 12) and in the larger group of survey participants (x̄ = 13.1, s = 11.2, n = 52) were not significantly different (p = 0.905). Nine of the twelve interviewees and correspondents (75.0%) indicated a major or minor degree concentration in chemistry, a percentage slightly greater than, but not inconsistent with, the 69.2% rate evinced by all survey participants. Degrees held ranged from bachelor's to doctorates. Educators from rural, suburban, and urban schools were represented, including public, private secular, and religious-affiliated institutions.

Operational definitions

At no point in the investigation were participants provided with the researchers' definition of “demonstration”. Responses to interviews and extended questionnaires suggest that teachers and their students view demonstrations to be presentations, wherein the teacher, or a small group of students, performs an activity for the remainder of the class to view—a classification consistent with that of Taylor (1988). Under this definition, demonstrations are viewed as distinct from laboratory investigations in which students, as individuals or in small groups, manipulate equipment, collect data, and perform analysis. The remaining survey participants, however, were not asked to provide a definition of “lecture demonstration” and may interpret the practice differently.

Findings

Fifty-two of eighty-eight chemistry teachers randomly selected from a nationwide database of high schools returned completed surveys. Twelve survey participants subsequently completed extended questionnaires describing their experiences with, and rationales for, employing lecture demonstrations.

Four of the survey items addressed the perceived effect of classroom lecture demonstrations on students' performance on homework assignments, laboratory work, and exams, as well as their understanding of course concepts. Another four survey items addressed chemistry teachers' perceptions of the effect of classroom lecture demonstrations on students' motivation to perform well on homework assignments, laboratory work, and exams, and to study the subject further through additional coursework.

Perceived effects on learning and motivation

Survey items 1–4 addressed the perceived effect of classroom lecture demonstrations on students' performance on homework assignments, laboratory work, and exams, as well as their understanding of course concepts. Mean scores for these items, along with 95% confidence intervals and standard deviations, are shown in Table 1.

Table 1 Perceived effects of lecture demonstrations on student performance

Number of item scores (n)	Mean of item scores (x̄)	95% confidence interval (α = 0.05)	Standard deviation (s)
1. How are students' homework assignment scores affected by viewing classroom demonstrations?
52	3.90	±0.20	0.72
2. How are students' lab assignment scores affected by viewing classroom demonstrations?
52	4.27	±0.15	0.56
3. How are students' exam scores affected by viewing classroom demonstrations?
52	4.10	±0.15	0.57
4. How is students' understanding of chemistry concepts affected by viewing classroom demonstrations?
52	4.35	±0.17	0.62

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Items 5–8 addressed chemistry teachers' perceptions of the effect of classroom lecture demonstrations on students' motivation to perform well on homework assignments, laboratory work, and exams, and to study the subject further (through additional coursework); mean scores, 95% confidence intervals, and standard deviations are shown in Table 2.

Table 2 Perceived effects of demonstrations on student motivation

Number of item scores (n)	Mean of item scores (x̄)	95% confidence interval (α = 0.05)	Standard deviation (s)
5. How is students' motivation to perform well on homework assignments affected by viewing classroom demonstrations?
52	3.54	±0.18	0.67
6. How is students' motivation to perform well on lab assignments affected by viewing classroom demonstrations?
52	3.83	±0.19	0.71
7. How is students' motivation to perform well on exams affected by viewing classroom demonstrations?
52	3.60	±0.18	0.66
8. How is students' motivation to study this subject further (additional courses at this school or beyond) affected by viewing classroom demonstrations?
52	4.35	±0.17	0.62

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Additional survey results

Results from open-response survey items indicate that most teachers who returned the survey had witnessed chemistry demonstrations as students (37 of 49, with three respondents unable to recall). All but one of the respondents (51 of 52) indicated that they perform lecture demonstrations as part of their own chemistry instruction; the sole participant who did not employ lecture demonstrations was a first-year teacher with a mathematics specialization who expressed an intention to include demonstrations in future chemistry teaching. The reported frequency of demonstrations ranged from less than one per month to more than four times per five class meetings, with a mean of 1.41 demonstrations conducted per week (s = 1.08). The teacher-reported frequency with which lecture demonstrations are conducted is congruent with the student-reported frequency in Tai and Sadler (2007), who determined a mean of 1.8 demonstrations per week (s = 1.2).

All participants indicated that they planned to maintain or increase the number of lecture demonstrations they perform. The reported amount of total science teaching experience ranged from 1 to 44 years (x̄ = 15.6, s = 11.2, n = 52), with specific experience in teaching chemistry also ranging between 1 and 44 years (x̄ = 13.1, s = 11.2, n = 52). A variety of degree specializations were reported, with 36 of 52 surveyed chemistry teachers (69.2%) indicating a degree featuring a major or minor concentration in chemistry or in a closely-related field such as chemical engineering or biochemistry.

Each of the participants in the survey (n = 52) expressed intent to maintain or increase the number of classroom demonstrations to be performed. Such a finding is not unexpected, given the enthusiasm for demonstrations evinced in the scores provided in the selected-response section of the survey, but the absence of any plans to decrease the number of demonstrations is noteworthy. The single chemistry teacher proposing that chemistry demonstrations might have some negative effect (perceiving slightly negative effects on students' homework and exam performance, as well as slightly reduced motivation to perform well on exams) nevertheless plans to increase the number of classroom demonstrations from “at least tw[o] every [three] weeks” to “at least one every week”. Multiple attempts to contact this individual to further discuss this incongruity were unsuccessful.

For each survey participant, the scores of the four items related to teachers' perception of students' performance were totaled to produce a performance category aggregate. The mean of aggregate scores for performance-related survey items was x̄ = 16.9 (±0.5, α = 0.05, n = 52), with a standard deviation s = 1.7. An aggregate score for items related to student motivation was also determined for each participant; the mean of aggregate scores for motivation-related survey items was x̄ = 15.3 (±0.5, α = 0.05, n = 52), with a standard deviation s = 2.0.

Survey participants tended to view the effect of lecture demonstrations on students' performance to be somewhat greater than the effect on motivation. The confidence intervals of the mean aggregate scores for performance-related items and for motivation-related items do not overlap at the α = 0.05 level, indicating that the category means are significantly different (Knezevic, 2011). The confidence intervals of the mean scores for lab performance and lab-related motivation do not overlap at the α = 0.05 level; likewise, there is no overlap in the α = 0.05 confidence intervals of the mean scores for exam performance and exam-related motivation. In both categories, the difference in the mean scores for the related items is statistically significant (Knezevic, 2011). The significant difference in the means suggests that the survey participants considered motivational effects at least somewhat independently of performance effects, and so did not automatically select the same scores for items related to motivation as were assigned to items related to performance. The confidence intervals of the mean scores for perceived effects on homework performance and perceived effects on motivation to excel on homework assignments overlap slightly, and one cannot determine whether differences of these mean values is significant (Knezevic, 2011).

The Pearson product–moment correlation between teachers' previous exposure as students to lecture demonstrations and their current use of demonstrations was calculated using forty-three pairs of data; nine educators had not provided quantifiable answers to either open-response items related to frequency with which demonstrations were viewed or are performed. A coefficient of r = 0.513 was calculated, with a corresponding effect size r² = 0.263. Frequency values were approximated by the authors from subjects' self-reported experience; the lack of precision in the recorded values undermines any confidence in the calculated correlation.

As teachers' assessments of their own practices are likely to be more accurate than their recollection of their experiences as high school students, the authors have some confidence in the numerical values reported for teachers' frequency of use of lecture demonstrations. The Pearson correlation was determined between the self-reported number of demonstrations performed per week and their years of chemistry teaching experience. From a set of forty-seven data pairs (with five teachers not articulating a sufficiently specific frequency of demonstration performance), a correlation coefficient r = 0.252 was calculated. The low value of r, and the correspondingly weak effect size r² = 0.064, indicate little correlation between teachers' years of chemistry teaching experience and frequency with which classroom demonstrations are performed.

Thirty-six teachers in the survey group self-reported a major or minor concentration in chemistry or a related field (such as biochemistry or chemical engineering) and received a degree-category score of 1. The remaining sixteen teachers who indicated degrees in other fields received a degree-category score of 0. After removal of data for the five respondents who had not provided a quantifiable answer describing the number of demonstrations performed per five class days, forty-seven data pairs were available to determine a point-biserial correlation. The correlation coefficient was calculated to be r = 0.294, with an effect size r² = 0.086, indicating at a maximum a small relationship between chemistry teachers' educational background (presence or absence of a chemistry major or minor) and frequency with which lecture demonstrations are performed.

The absence of any strong correlations found in the data can be traced to two factors: the tendency of nearly all of the survey participants to conduct classroom demonstrations, and the realistic limit to the number of demonstrations that can be performed each week as part of the instructional process. With minimal variation in the frequency with which lecture demonstrations can be performed, and with 73.1% of survey participants (38 of 52) indicating that they perform demonstrations at least once per ten class meetings, little dependence on educational background, years of chemistry teaching experience, or previous exposure to classroom demonstrations should be anticipated.

Teacher commentary

Although the selected-response items of the survey did not specifically invite elaboration, a few of the respondents included comments that provided some justification of their numerical responses. Such commentary tended to support statements made in their responses to open-ended questions related to the frequency of current and future use of lecture demonstrations. One survey respondent declared that “after doing this survey, I am inclined to do more [demonstrations];” another averred that “I plan for them to get better every year, just like me”, and a third asserted: “wish I had time to do a demonstration a day!” Several respondents clearly articulated the philosophy underlying their use of classroom demonstrations, offering statements such as “[i]deally, all lessons should be demonstrated. Students LOVE the demonstrations and do understand the concepts taught much better”, “my students remember years after having my classes the demos that I did” and “critical for student interest… [I] try to make them a priority”.

Other educators expressed more nuanced views of the benefits of demonstrations: one participant maintained that “[s]tudents like most of them, but… learn best about the topics and thinking critically by doing labs and applying concepts…”, while another indicated that “[i]f I believe it will benefit and enhance my students' conceptual understanding… I would add new ones”. Even the forty-two year veteran who flatly stated that “I know that demonstrations help concept development” added that learners “are either motivated to do well… or not. If they have little interest, demonstration[s] don't seem to have much effect”. Only one commenter expressed a neutral perspective; despite her occasional (once per week) use of demonstrations, and a strongly positive view of their effect on students' performance, this teacher's clearly-articulated conviction was “I feel student hands-on labs are better”.

Teachers' approach to demonstrations

Participants in the extended questionnaire were asked to describe their approach to lecture demonstrations. Descriptions of the demonstration process included presentations where the teacher, “as the leader of the classroom, display[s] a chemical concept for students” and activities that “[the teacher] or a group of select students conduct[s] for the classroom as whole”. The former definition is offered by Mr Anand†, who has five years of chemistry teaching experience and is currently employed to teach more than 300 students each day in an urban public high school, while the latter is the view of Ms Bayne, a four-year veteran teaching in a suburban public school. Such characterizations distinguish lecture demonstration from student-centered activities such as laboratory work, and support the definition proposed earlier: that demonstrations are organized and presented by the teacher, with the main body of students acting as an audience.

As part of their definitions of “demonstrations”, many interviewees and correspondents offered justifications for the use of lecture demonstrations in chemistry classrooms. Most of the rationales addressed pedagogical issues, such as “to provoke students’ thinking”, “to clarify specific information”, “to connect the theoretical aspects of a lecture to real life”, and “to delve deeper into or simply illustrate a topic”. Other reasons emphasized the entertaining aspect of demonstrations. Mr Collins, a twenty-three-year veteran teaching in a suburban public high school, believes that “[t]he teacher[s] should have some entertainer in them… this is why I do a ‘WOW’ demonstration the first day of class… to have them enjoy the class…” while Ms De Burgh, with one year of chemistry teaching experience in a religious-affiliated private school, asserts that “[d]emonstrations that are exciting (fire, sound)… are often the ones that help… students become the most engaged and inspired…” Ms Elkins, who teaches at a suburban public high school and has seventeen years of chemistry teaching experience, believes that “[c]hemistry demonstrations must be smelly, smoky, explosive, or colorful! There is an inherent attention grabbing and entertainment factor in many good chemical demonstrations”.

Even where the entertainment value of lecture demonstrations is highlighted, veteran and novice teachers alike tended to stress the instructional aspects of demonstrations. Ms De Burgh intends demonstrations to prompt students to “figure out what happened”, particularly when “a surprising result” is observed. Dr Ferguson, a twenty-year veteran teaching at a secular private school, “may sometimes perform demonstrations [specifically] to being out… misconceptions” and wishes students to “see the connection to the theoretical”; Mr Geddes (who has taught chemistry for four years in an urban high school) indicates a desire to provide “tangible experiences, so that the course is not abstract”. Mr Geddes particularly emphasizes the use of demonstrations to bring about

a particle-based understanding of the world. Most of the best demos at some level help to crack into that. …Students need to see stuff… because if you just tell them… they don't believe it, and if you test them on things like this later, they'll put their original beliefs down, because misconceptions are hard to break.

Student engagement appears to be an important consideration, apart from any diversion that demonstrations might create. Ms Heroux, who has taught chemistry for five years at a private religious school in an urban setting, says (twice) that a successful demonstration requires “enthusiasm on behalf of the teacher”. Mr Jeffords, with thirty-two years of chemistry teaching experience in a rural public school, bluntly states: “if I can't get their attention… I can't teach them anything”. Given the perception that lecture demonstrations increase chemistry students' motivation, the aforementioned opinions are unsurprising, but do indicate the conscious effort on the part of educators to make demonstrations educationally meaningful as well as appealing.

Connections to laboratory activities

The authors postulated that some chemistry teachers might use lecture demonstrations in lieu of students' laboratory experiences, and all interviewees and correspondents indicated that although laboratory activities were preferable, occasional replacement of lab work with demonstrations was appropriate and necessary. Many of the teachers who answered the extended questionnaire articulated the same reasons for such substitutions: safety concerns that arise when inexperienced or careless individuals handle reactive substances or delicate equipment, and cost considerations where larger classes and less-affluent institutions preclude broader-scale investigations. Ms De Burgh was the only correspondent, however, to propose (albeit with reluctance) another practical reason to employ demonstrations in place of student laboratory work:

I am frequently torn between wanting to show more demonstrations and wanting to do more labs. I think a lot of teachers rely on demos because labs are so time consuming. …I often too feel drawn to rely on demonstrations when I cannot take prepping or cleaning up another lab.

Other participating chemistry teachers mentioned the opportunity to augment students' laboratory work with demonstrations that address safety procedures or introduce lab skills, using demonstrations in combination with, rather than in lieu of, laboratory investigations.

Concepts addressed through demonstrations

Varied opinions were noted regarding concepts effectively and ineffectively addressed via lecture demonstrations. Whereas one correspondent (Ms Murray, who has nine years of chemistry teaching experience in a suburban public high school) indicated that demonstrations related to bonding were particularly effective, another (Mr Jeffords) suggested that bonding and molecular geometry were ineffectively demonstrated and “more difficult to do”. In this instance, the two may simply be applying different definitions, such that passive observation of ball-and-stick or space-filling schematics might represent a demonstration using one educator's definition, but might not according to another's. Regardless, the lack of consensus regarding the applicability of lecture demonstrations to particular topics—along with the negative effect of frequent demonstrations on students' subsequent performance observed by Tai and Sadler (2007)—suggests a rich opportunity for further study.

The effect of increased classroom technology on the implementation and efficacy of lecture demonstrations appears to be a function of the extent to which such technology is available to teachers. Those with access to resources such as classroom computers, Internet connections, and projecting equipment can share recorded images or programmed models to illustrate concepts. As Ms De Burgh notes, “I tend to show videos of the more dangerous reactions… I have the ability to show videos of things… which I do not have the [means] available to demonstrate” personally. Ms Heroux observes that “the range of demonstrations… has increased drastically. Now we can watch demos [online]” for processes for which “I don't have the resources to do the demo myself… it has truly changed the dynamics of teaching”.

Not all interviewees and correspondents view technology as necessarily superior to the “live” demonstration. Veteran Mr Jeffords states that “[t]here are short demonstration videos [for processes that] can also be done in the classroom”. This sentiment is supported by Mr Kemp, a twenty-two-year veteran teaching in a suburban public high school, who describes the demonstration process as involving “[s]tuff we use every day—it's nothing high-tech; it's the lowest tech we can find. Kids are still amazed by the simplest things…”

The role of students during demonstrations depends on the amount of control the teacher wishes to assume. Mr Anand prefers students to be “active watchers”, while others expect students to “participate…[s]ometimes… actually perform the demo once I model it” (Ms Elkins). Regardless, all interviewees and correspondents demand that students be thoughtful observers; Ms De Burgh attempts to have “students… uncover the explanation rather than [be told] what happened”. The demonstrator's role is perhaps best articulated by Dr Ferguson, who indicates that the instructor is typically “asking students questions about what is being done, what is occurring, what are some extensions” to the concepts being demonstrated. Once again, participants in interviews and correspondence reveal their intent to use demonstrations to reinforce ideas, rather than merely producing entertaining diversions.

Pedagogical value

When asked about their favorite demonstrations to perform, teachers invariably focused on the spectacular, choosing words such as “explosive”, “dramatic”, and “impressive” and citing students' positive responses. Mr Kemp favors demonstrations that produce “something that's sensational… a show and tell—something I use to motivate and captivate the kids.…Whatever is in line for the task of the day—show them what you're doing”. Ms Levinson, who has taught chemistry at a rural public high school for eleven years, enjoys the fact that students “can actually see something happening”. Once again, student engagement is put forth as the primary reason for performing these demonstrations. Ms Murray emphasizes the benefit of a “discrepant” demonstration outcome, which “generates a lot of discussion, and is absolutely necessary for understanding lots of concepts”. Some interviewees and correspondents have performed lecture demonstrations outside the regular classroom, either because of safety concerns or to stimulate interest in those not currently enrolled in chemistry courses.

At least one individual believes that experiencing demonstrations as a student spurred his own desire to study chemistry further. Dr Ferguson states that “[d]emonstrations I saw may have helped me understand the concept, but [most significantly] probably got me excited about chemistry… [p]robably the reason I became interested in chemistry and got me to become a chemistry teacher”. Dr Ferguson is convinced that demonstrations have had a lasting effect on learners: “students move on, graduate, and [when] I cross paths with them, they remember that flame test that I did for them; they may not remember the chemistry, but they remember the demo”, and recalls a comment from a specific student, who indicated that lecture demonstrations “sparked my interest and [inspired] me to delve a little deeper into chemistry… to pursue a career in a chemistry-related field.”

Conclusions

Summary of findings

Perhaps the most noteworthy outcome of this study is the evidence for the pervasiveness of lecture demonstrations. Even if all of those teachers who chose not to participate in the survey disqualified themselves because they do not perform demonstrations—a highly speculative assumption—almost 60% of chemistry teachers contacted perform and value classroom demonstrations. Quantitative survey data—along with qualitative data from surveys, structured correspondence, and interviews—suggest that the use of lecture demonstrations to supplement instruction in chemistry classrooms is nearly universal.

Survey participants, correspondents, and interviewees expressed their belief that demonstrations improve students' performance on practice assignments, laboratory investigations, and exams, as well as enhancing students' understanding of concepts. Students' motivation to perform well on assignments, laboratory exercises, and exams, and to enroll in further coursework related to chemistry, was also perceived to be improved by the use of lecture demonstrations. The effect on motivation was perceived to be significantly less than the effect on performance.

No correlations were observed between teachers' prior exposure to lecture demonstrations as students and their current use of demonstrations, between teachers' years of chemistry teaching experience and the frequency with which they perform lecture demonstrations, or between degree specialization (chemistry vs. non-chemistry) and the frequency of use of demonstrations.

Little familiarity with published research related to the effectiveness of lecture demonstrations was reported by teachers in the survey. The discrepancy between teachers' perceptions of the benefits of demonstrations and students' subsequent performance in introductory college chemistry courses indicates opportunity for further research toward best practices related to lecture demonstrations.

Recommendations

Whether classroom demonstrations truly lead to increased student performance and motivation cannot be determined from teachers' opinions, no matter how fervent their faith in the efficacy of their methods. Indeed, the high value placed on lecture demonstrations by teachers in this study is contradicted by the findings of Tai and Sadler (2007), although Tai and Sadler suggest that “current high school practice with regard to demonstrations”, rather than the mere inclusion of demonstrations in the high school classroom, may be the reason for the negative correlation with students' performance in their introductory college coursework. The results of the current study suggest much opportunity for research of effective demonstration methods toward measurable learning gains.

Tai and Sadler (2007) point out that their study “does not address the issue of student interest and continuation in chemistry… The impact of demonstrations might be associated with student continuation in chemistry from high school to college”. We agree with Tai and Sadler's recommendation that any connection between lecture demonstration and students' interest in additional study of chemistry be further investigated.

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Footnote

† Pseudonyms are used to protect the identities of all participants.

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