Article pubs.acs.org/jchemeduc
Changing the First-Year Chemistry Laboratory Manual To Implement a Problem-Based Approach That Improves Student Engagement Thamara Laredo* Departments of Interdisciplinary Studies and Chemistry, Lakehead University, Orillia, Ontario L3V 0B9, Canada S Supporting Information *
ABSTRACT: For students who are not science majors, problem-based (PB) laboratories for first-year chemistry provide a more comprehensive experience than conventional expository ones. Implementing PB labs is reasonably easy, as the lab experiments may not need to change; what changes is the way the lab manual is set up and how the actual session is carried out. Rather than having a step-by-step procedure, the PB manual has general guidelines for the experiment, enabling students to develop experimental procedures of their own. During the lab session, a prelaboratory discussion is driven by the students’ input and clarifies the details for each individual procedure. In addition to the engagement of the students in the lab, the result of this approach has been the development of students who are capable of formulating hypotheses and, more importantly, sound experimental procedures to test these hypotheses.
KEYWORDS: First-Year Undergraduate/General, Laboratory Instruction, Problem Solving/Decision Making, Inquiry-Based/Discovery Learning, Laboratory Management
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INTRODUCTION
One of the main obstacles to the concept of PBL in a laboratory setting is the issue of safety. True inquiry means that students are free to choose their own problem to investigate, and that they are able to steer their questions in the direction of their choosing.5 However, such freedom cannot exist in the laboratory, where inappropriate decisions can result in dangerous outcomes and unforeseen consequences. The problem, however, can be solved by supplying the students with guidelines on what they will be investigating, as opposed to the more traditionally scripted step-by-step instructions. The guidelines are clear indications as to what the experiment is trying to achieve, but without going into detail. Providing these guidelines narrows the students’ choices of possible options, which increases laboratory safety while still allowing students the freedom to plan the experiment and procedure in order to successfully study the phenomenon at hand. During the past year, I have implemented problem-based laboratories with students who are not science majors and have noted great improvement with respect to previous cohorts. For example, previous cohorts have shown difficulties in grasping experimental procedures, whereas the cohort that learned under a problem-based (PB) environment was engaged and demonstrated better understanding of experimental methods. Reviews from students regarding the labs have been excellent. Importantly, students who are retaking the first-year chemistry course, and so have experienced both the traditional and PBL approaches for similar content, have shown an increased level of engagement and positive attitude toward the labs. Students
The laboratory component of any science course is a longestablished way of teaching students more than just concepts. Labs are a way of not only visualizing and strengthening theories learned in the classroom, but to gain agility in handling lab equipment. Traditional chemistry labs are expository in nature and have sometimes been described as cookbook-type recipes, in which the most important aspects are first, to gain dexterity, and second, to test a theory.1−3 Although this type of lab may be perfectly suited for students in a chemistry program, other students may only ever take a single general chemistry course. This is particularly true for students who are not science majors and who are taking chemistry as an elective. For these students, the purpose of the chemistry lab should be one of experimentation in itself; a problem-based approach to the scientific method. In the sciences, problem-based learning (PBL) plunges students into the scientific method by making them formulate proper scientific questions and hypotheses that can be properly disproven if the results indicate so.2,4 In an experimental context, PBL first focuses on understanding the differences between qualitative and quantitative information, and then in the concepts of dependent and independent variables, blanks, standards, and controls. Although these concepts will be clear for the majority of students who take more than one laboratory course during their studies, using the first-year chemistry laboratory course to emphasize these concepts may prove invaluable for those students in liberal arts programs or schools that do not have a strong science component in their course offerings. © XXXX American Chemical Society and Division of Chemical Education, Inc.
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who successfully finish the course are able to formulate a hypothesis and propose a sound experimental method to test it. This paper explains how the lab manual differs from traditional step-by-step manuals and how the actual laboratory session is conducted in problem-based laboratories.
12 chemistry. Aside from the lecture content (which is meant to be in line with the labs) and the experiment guidelines, the students receive no additional information for the procedure writeup. Lecture content includes theories, exercises, and sample problems and sometimes a brief explanation of the physical principles behind a specific technique that will be used in the lab. However, the experimental details and overall implementation of lab techniques are not discussed in class. The PB labs are based on the students’ ability to inquire on their own.
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THE PROBLEM-BASED LAB MANUAL The introduction section of the lab manual of PB experiments explains what makes this manual different from more traditional ones. The focus of the lab is for students to be able to create a scientifically sound experiment rather than simply follow a set of instructions. Moreover, the aim is to make students aware that the main goal is to guide them toward being proficient experimentalists, and that the final result of their report calculations is secondary (and will follow from a good experimental design). The introduction also provides general safety rules of the lab, explains the purpose of the prelab assignment, and lists the parts the students should include in their reports. The laboratory experiments in the PB manual are similar to those of traditional first-year chemistry, making implementation quite easy. For the first half of the course (fall term), the experiments progress from qualitative, to semiquantitative, to quantitative. In the second half (winter term), all experiments are quantitative in nature. Box 1 shows a partial list of the
Prelaboratory Questions
The majority of the traditional lab manuals have prelaboratory assignments for the students to complete before the experimental process is carried out. Usually, these questions include a calculation similar to the one they will be doing in their final report and questions about the purpose of specific steps of the experimental procedure.6 One of the main drawbacks with traditional step-by-step lab manuals is that students do not need to be prepared ahead of the lab period to be able to perform the lab. Even when a student has fulfilled the prelaboratory assignment, that student can move through the lab steps of the experimental procedure without a strong understanding of the purpose, which can result in frustration, confusion, and the disengagement of students. In this scenario, the student’s realization of the experiment’s meaning likely comes during the report writeup when he or she is forced to use the collected data to calculate a final result. This is not only frustrating for both student and instructor, it also weakens the purpose of visualizing and improving understanding of the lecture content, which is the main purpose of any lab component. The prelaboratory assignment phase of PB laboratories is composed of a two-part preparatory process. Students are asked to first write, in their own words, the experiment’s purpose, which is meant to connect the phenomenon under study with the experiment’s objectives, and second, to write a proposed procedure, including the independent and dependent variables that will be monitored in the experiment. This pushes students to think about what the experiment will accomplish, and how it will be done, before the experiment is even conducted. Providing students with the opportunity to write the procedure inherently makes them aware of what they will be doing in the lab, both in terms of the steps involved and in terms of the purpose. This phase of the preparation is especially important because the steps and purpose are not otherwise explicitly written in the manual. Grading the prelaboratory assignment is mostly based on completion (rubrics are available in the Supporting Information), and as the term progresses, students improve greatly at defining variables, suggesting blanks, and writing coherent procedures based on the materials at hand. The prelaboratory questions are handed in by the students a day before the lab. The purpose of this is twofold: first, it forces the students to prepare for the lab a day ahead; second, it allows the instructor to grade the assignment before the students come to the lab. The immediate turnaround for marking (the next day) and the prelab preparation are the biggest drawbacks for the instructor. However, the prelab is usually short and grading is not intensive. This is a critical component to the PB approach and the success of the student.
Box 1. Partial List of Problem-Based Experiments 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.
Leaves are green Conductivity and ionic compounds Understanding the concepts of accuracy and precision Understanding the concept of dilution Controlling the limiting reagent Recycling aluminum Heat, energy, and a cup of coffee Salt in the winter How to measure the capacity of a buffer? Acid content of a carbonated beverage Understanding electrochemistry Solubility, equilibrium, and thermodynamics
problem-based experiments. Any given PB experiment in the manual has the following parts: introduction, objective(s), safety, materials available, and guidelines. Two or more prelaboratory questions and topics to consider after the experiment, guide the experiment and report writeup. The introduction section explains in lay terms why the concept explored is important in an everyday setting. In two or three sentences, the objective summarizes what will be done in the lab, but does not give the purpose of the experiment. Safety includes waste disposal and special handling instructions. The main aspect of any experiment is the guidelines section. Here, students are provided with general directions as to how to accomplish the objectives of the experiment. Within the guidelines, students are also asked direct questions about whether they need a blank or control and what that would be; or how would they achieve a specific subtask within the procedure. For example, in the experiment on acid content of a carbonated beverage, the guidelines indicate that students need to remove the CO2 from their solutions. With the list of materials available, students are expected to propose a way of accomplishing this. It should be noted that the prerequisite for the first-year chemistry course at Lakehead University is grade B
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used as a control.7 For this, the students were presented with one experiment in which the procedure was fully laid out for them. Although most students liked the fact that their prelaboratory assignment for that day was short (they did not have to devise a procedure), in general, they also agreed that they felt “lost” during the experiment compared to the sessions in which they had written their own procedures. A student noted in the rating (consent has been given for publication): I have enjoyed the [labs] where we came up with our own procedure. [...] In the other labs, it was much easier to understand all aspects of the experiment, even small aspects like why the addition of water matters or not. [...] The main concept is also easier to understand in the other labs. This lab demonstrates redox reactions and acid−base reactions, but it is not as easily demonstrated in the lab because we are focused on getting the alum. Additionally, students were given a surprise quiz for this “control” experiment. The quiz consisted of two questions: (i) Using drawings or bullet points, propose a coherent procedure for today’s experiment; and (ii) Why do you need to add sulfuric acid to the reaction? Most of the students were able to answer question two and expressed that a neutralization had to occur during the reaction. However, in regards to question one, only 2 out of 10 students could propose a basic procedure on how to accomplish the synthesis of alum from aluminum, and none could provide all the key steps (dissolving in basic medium, adding excess acid, heating, crystallizing, and filtering), even though this was the penultimate experiment of the term. When the lab experiment is written as a step-by-step set of instructions, students rely more heavily on the instructions than on their own critical-thinking abilities; this is in direct contrast to the PB labs, in which, by the end of the term, students are capable of writing a coherent procedure based on general guidelines.
PROBLEM-BASED LABORATORY SESSIONS The PB lab session is divided into two components: (i) the prelaboratory discussion, which is student-driven, and (ii) the experimental portion. The prelab discussion lasts for 45−90 min, averaging ∼60 min. In comparison to traditional labs, this division of time may seem to reduce the time available for the experiment. However, spending a significant portion of the lab period in the prelab discussion ensures that the students understand the purpose and the procedure of the experiment, as well as allowing them the possibility of exploring their own ideas, safely. This prelab discussion is not a lecture; it is guided by students, and as such, it should be considered an initial inquiry phase. Anything that is written on the whiteboard comes directly from the students’ answers, such as: purpose of the lab, dependent and independent variables, blank and number of repetitions. The same is true for the proposed procedure, with the added condition that the only materials available are those listed in the manual. During the prelab discussion, the students are constantly taking notes and modifying their own procedures accordingly. Something that often happens during the prelab discussion is that students offer varied (and quite feasible) ideas on how to accomplish a particular task of the procedure. Additionally, during this phase of the lab session, small demonstrations on how to use specific equipment may occur. Upon completion of this prelab phase, students will have different procedures that they can follow, or diverse samples of their choice. An evident outcome of the prelab phase is that students understand how they will approach the experiment; they ask fewer questions during the experimental part, they act more confidently, and they are aware of the expectations to successfully complete their final reports. The experimental part of the PB labs is quite similar to traditional labs in that students are following steps to attain a desired outcome. However, the steps are inquiry based and written by the students, so not all students may follow the same set of steps.
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CONCLUSION Traditional first-year chemistry labs provide a clear visualization and application of phenomena studied in the lectures, as well as the basis of dexterity for future lab courses, especially for students in a chemistry or chemistry-related major. However, when first-year general chemistry is the only lab course that students will take during their undergraduate degree, the goal of the lab component shifts to not only fulfilling the two conditions above, but more importantly, to teaching students how to propose sound experiments to test valid hypotheses. Successfully mastering such a skill is not limited to the sciences, but to practically every aspect of human knowledge. The problem-based approach described here shows how providing students with the freedom to create their own procedure works toward improving this ability. At first, however, the students may show some discomfort in the method, as noted by one biology-specialization student taking chemistry for the first time: The most frustrating part of the lab was the prelab. I thought it was difficult trying to figure out a procedure when we were using equipment that I had no idea how it was properly used. I knew why we used it, but not how. [...] I find the lab to be like inquiry-based learning and this is very difficult for me. I think it’s very hard for me to know the purpose of each material and to make connections. However, as the students improve in their ability to develop a procedure, they find the PB approach much more engaging. The same student commented at the end of the term:
Student Feedback
To gain some feedback of the PB approach to the experimental component of the course, students were asked to provide a rating of the laboratory session in each report. It was made clear from the beginning that the rating mark was based on completion of the rating section of the report, regardless of how positive or negative the rating was. It was explained that the rating was the student’s way of providing important feedback and a voice to improve the quality of the labs, and that any suggestion would be considered accordingly for future sessions. Although sometimes the feedback was related to the lab equipment, and little could be done to enhance that, some of the feedback was constructive and helped adjust the manual. As an example, the list of available materials was a suggestion from one of the students. The student wrote in the rating that, although she had understood the lab procedure after the prelab discussion, she found it too hard to figure out the steps just having guidelines, and that maybe knowing what she would be using would allow her to visualize the procedure better. When students were presented with a list of available materials for future labs, several pointed out in the rating that they thought that the list was a useful addition to the lab manual that helped them in proposing a logical experimental procedure. The feedback was also useful in assessing the students’ comparative opinion of a traditional step-by-step lab, which was C
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I had never done a lab like that before (where you have to prepare the procedure). Getting used to it, I now really enjoy every lab. Very practical and it makes you think about everything. Programs such as interdisciplinary studies, arts and science, or liberal arts, would benefit from the problem-based approach for chemistry labs, as the emphasis is placed on the process of experimentation rather than on the product outcome, a positive condition that inevitably leads to enhanced critical thinking.
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ASSOCIATED CONTENT
* Supporting Information S
Example course laboratory manual and sample student work including a grading rubric. This material is available via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
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