Laboratory Courses for Pre-Service Chemistry Teachers Between Acquisition of Skills and Didactic Double Decker

Abstract

For their future profession, pre-service chemistry teachers need to acquire practical skills during their university studies. In this article, the development, use and evaluation of several laboratory courses that aim at the acquisition of experimental competencies are described and discussed. During their bachelor’s studies, students take laboratory courses in general, inorganic, organic and physical chemistry and a research internship. During their master’s studies, students take one laboratory course in organic chemistry. To evaluate these laboratory courses, quantitative and qualitative research approaches were used. As the results of those evaluations show, the students are content with the courses and rate them as relevant for their future profession. The courses often use methods and tools that pre-service chemistry teachers can also use in their future profession in schools; such methods and tools serve as a didactic double decker, which means that pre-service chemistry teachers use their experiences as a student later in schools as a teacher. To further develop the laboratory courses, this idea will continue to be considered.

1. Introduction

“Graduates have relevant scientific and didactic knowledge in chemistry, they know the essential cognitive methods and methods of working of chemistry and can experiment safely” [1]. This quote from the subject profiles in teacher training underlines the importance of experimental skills for pre-service chemistry teachers. They must be able to demonstrate experiments and to guide their students to experiment. Because “the professional quality of teachers is determined by the quality of their teaching” [1], universities are responsible for ensuring that during their studies, pre-service teachers acquire the specialist knowledge, competencies and skills, for example practical laboratory skills, they need for their future profession. Therefore, the acquisition of practical skills during several laboratory courses is described and discussed in this paper. The courses were designed in such a way that they use methods and tools that pre-service chemistry teachers can also use in their future profession at school.

Learning in the laboratory means more than the acquisition of experimental skills. Learning outcomes can be summarized as experimental competencies (for example, practical skills), disciplinary learning (for example, theory–practice connection), higher-order thinking skills (for example, problem solving), transversal competencies (for example, collaboration and communication) and the affective domain (for example, self-efficacy and motivation) [2]. Education in the laboratory should support students’ development of higher-order competencies and the understanding of the nature of scientific inquiry [3]. If several laboratory courses are part of the curriculum, which is common in chemistry degree programs, then the curriculum model of Seery et al. [4] can be used for planning such courses. The model focusses on learning progression during laboratory courses leading to a master’s degree. Starting with the development of experimental skills, then predicting and interpreting experiments using prior knowledge and designing experimental approaches (first for familiar and then for unfamiliar designs), the last level is scientific research, where the students design protocols for an unfamiliar topic [4]. If students are involved in inquiry-type activities, they develop high-level learning skills and metacognitive abilities [5]. Students should be trained in inquiry-based approaches, otherwise they will face difficulties when they come to use such approaches [6]. Examples of inquiry-based learning in laboratories, at school and at university can be found in the literature. For students at school, inquiry-based learning can be promoted by using multitouch instructions as scaffolds [7]. For students at university, it can be promoted by mini-lab activities, where students are led by questions during their observations of experiments [8]; by supporting the students’ exploration of how a major product is produced [9]; or by allowing different outcomes in an experiment [10].

At German universities, pre-service teachers study two different subjects, for example, chemistry and history, and educational sciences. For each subject, courses on subject-specific and didactic topics are included in the university curriculum. To ensure that the workload does not become too high, the degree program is organized in such a way that students do not work more than someone working full-time. Therefore, only limited time is available for laboratory courses. At our university, the existing courses for pre-service chemistry teachers were reorganized to meet demand, and two new laboratory courses (research and organic chemistry for master’s students) were added to the curriculum.

Pre-service chemistry teachers differ from major chemistry students because they know exactly what profession they will pursue later. In developing curricula, the future profession should therefore be considered. Not only the content of a course but also the methods used are of interest because they especially can serve as a didactic double decker [11]. In such cases, students use methods for their own learning, which they can also use as chemistry teachers in schools for instructing the learning of their students.

2. Development of the Subject-Specific Laboratory Courses

At the University of Potsdam, six subject-specific laboratory courses are included in the curriculum for pre-service chemistry teachers (see

Table 1. Overview of the laboratory courses.

Course	Content	Duration	Localization
General chemistry (GC)	10 experiments on different topics, such as redox reactions, kinetics, and acids and bases	Four hours per week for 15 weeks; during the lecture period	First year (bachelor’s)
Inorganic chemistry (IC)	10 experiments on different topics, such as qualitative analyses of food and everyday materials	Four hours per week for 15 weeks; during the lecture period	First year (bachelor’s)
Organic chemistry (OC)	10 organic syntheses and five school experiments	Two weeks full-time; after the lecture period	Second year (bachelor’s)
Physical chemistry (PC)	Three experiments each for the topics of thermodynamics, reaction kinetics and electrochemistry	Three hours on nine dates; accompanying the lecture course	Second year (bachelor’s)
Research (R)	Research on different topics	90 h (individual time)	Third year (bachelor’s)
Organic chemistry (OCM)	School experiments for the topics of biological chemistry and sustainability	One week for six hours a day; after the lecture period	First year (master’s)

). During their whole studies, pre-service chemistry teachers have 257 h of laboratory time in total. On top of the subject-specific laboratory courses, didactic laboratory courses are included in the curriculum, which focus on school experiments and their didactic use.

The curriculum for chemistry lessons at school (for students aged 16–18 years) defines the following learning goals for their experiments [12]:

The students

• plan experimental or model-based procedures, also for testing hypotheses, statements or theories, taking into account the control of variables if necessary;
• carry out qualitative and quantitative experimental investigations—in accordance with chemical working methods and safety rules, record and analyze them;
• use digital tools and media for recording, visualizing and analyzing measured values and for calculations, modelling and simulations.

During their university studies, pre-service chemistry teachers must acquire the competencies they will need to teach their future students at school in such a way that they can achieve these learning objectives. Therefore, the laboratory courses focus not only on the content but also on the acquisition of skills and methods. In addition to practical skills, the students learn how to prepare for experiments, how to document the results and how to use digitalization.

Throughout the six laboratory courses, the students should continuously acquire practical skills. Learning opportunities include all experiments, preparation for the laboratory and the application of prior knowledge from the lecture courses. For example, prior knowledge should enable students to decide which solvent is appropriate for their experiment, or to explain the origin of a color change in an indicator they use for a titration.

Starting with the general chemistry course, where students learn how to handle chemicals and glassware, use the burner, prepare solutions and titrate, in the second course (inorganic chemistry) they can apply these skills to qualitative analyses, such as detecting nitrate ions in an analytical sample or in lettuce, and learn new techniques, such as the production, storage and use of hydrogen or the construction of a solar cell. In the second year, the organic chemistry course builds on all the skills learnt in the first year. Students also learn new techniques in typical or organic chemistry, such as distillation or recrystallisation. In physical chemistry, students apply the techniques they have learnt in the first three semesters, such as titration, and learn new techniques such as thermal analysis or potentiometry. Students acquire skills in measuring and recording data. In the last year of the bachelor’s program, students participate in a research internship with a research group at University of Potsdam or at another University (in Germany or abroad), depending on their interest. A research internship in industry or at any research institutions is also possible. Therefore, the skills that students acquire during their internship are very individual. During the master’s program, the students have only one mandatory laboratory course. Here, they can apply and refine all skills from previous years.

The methods used in the laboratory courses (including preparation and documentation) were chosen with students’ future profession in mind. Following the concept of the didactic double decker [11], methods were chosen that can also be used at school.

Table 2. Overview of all methods used in the laboratory courses.

Method	Laboratory	Preparation	Documentation	Courses
Pre-structured laboratory journal	x	x	x	GC, IC, PC
Laboratory journal or notebook (paper and digital)	x	x	x	GC, IC, OC, PC, OCM
Profession-orientated tasks		x	x	GC, IC, OC, OCM
(Interactive) videos with lab techniques		x		GC, IC, OC, PC
Interactive tasks such as building apparatus with Chemix [13]		x		GC, IC, OC
Digitalization (tablets, smartphones, thermal imaging camera, video, photo, spreadsheet, use of Moodle course)	x	x	x	GC, IC, OC, PC, OCM
Egg race	x			IC
Written protocol	x		x	GC, IC, PC
(Interactive) protocol checklist	x	x	x	GC, PC
Learning stations for preparing techniques		x		OC
Guided inquiry tasks for planning experiments		x		OC
Reflection tasks			x	OC, OCM
Evaluation of analytical data	x		x	PC, OCM

gives an overview of all methods.

3. Methods as Didactic Double Decker

In this section, an example of each method is described and discussed. Its function as a didactic double decker [11] will be made transparent by linking the competence the students acquire during their studies at university with their future profession as chemistry teachers at school.

3.1. Documentation

3.1.1. (Pre-Structured) Laboratory Journal

At school, students write protocols for their experiments, a task that is not very popular among them [14]. Even at university, students dislike writing protocols, probably because they do it at home during their own time. Therefore, in the organic chemistry laboratory course, another method of documenting experiments was used: a laboratory journal which is a common documentation tool in science. During the laboratory course, students use an A4 booklet to document the planning, conduct and evaluation of their experiments. The students write down their notes during the laboratory day. Only the components for their documentation are given including the name of the experiment, reaction equation, batch size, preparation notes including experimental set-up and implementation (these are the only tasks the students will complete at home), observation and evaluation, mechanism task and reflection task (see Section 3.1.2). Students make all other decisions regarding their documentation independently. For example, they can use prints or photographs of the set-up or photographs for their observations. They can also combine analogue and digital elements (for example with QR codes that link to photos). The degree of freedom and the parallel creation of the lab journal during the lay day ensure a better acceptance than traditional protocols (see Section 4.2 evaluation). An example of a more open approach for documenting experiments is given for their future profession.

In the first two chemistry labs, the general chemistry lab and the inorganic chemistry lab, students learn to document experimental activities, observations and results in pre-structured laboratory journals. The first analyses are also pre-structured. The degree of pre-structuring gradually decreases over the course of the first year of study, while the proportion of independent documentation by the students increases. In the beginning, the entire implementation is specified in detail, supplemented by notes and sketches of experimental setups. The students must only perform observation tasks, record measurements and analyze them in a guided way, e.g., by performing calculations using predefined calculation methods or plotting measurements in diagrams. After the first independent experiments, the tasks to be completed become more and more extensive and the assistance is reduced. This means that more and more information must be researched in preparation for the experiments, and more and more tasks must be prepared and followed up. During the first year, more and more reflective and profession-orientated tasks are added, in which the students are asked to reflect on the knowledge gained from the experiments in terms of how it can be applied in everyday life. For example, blackboard pictures should be prepared for the experimental knowledge. This allows students to familiarize themselves with how experimentally acquired knowledge can be clearly presented to pupils. The pre-structured lab journals and an additional interactive checklist with, for example, various digital tasks for formulating observations (see Section 3.2.2) help first-year students to create their first fully independent protocols. The pre-structured lab journals they have been working on so far provide information on what information needs to be documented during the experiment. For about a quarter of the 20 experiments to be carried out in the first year, complete protocols with introduction (including theoretical background), execution, experimental setup, observation, measurements (if applicable), evaluation and error analysis must be prepared on the basis of independent documentation. The use of an A4 booklet is recommended for this documentation. A similar procedure is recommended for schools. By using the pre-structured laboratory journals with an ever-decreasing degree of pre-structuring, our pre-service chemistry teachers directly learn a way of introducing pupils to the documentation and evaluation of experiments.

As the students progress through the chemistry program, support from pre-structured laboratory journals continues to decrease. In their second year, pre-service chemistry teachers have a lab course in physical chemistry. This lab course is designed for pre-service chemistry teachers as well as biochemistry and nutrition science students. To successfully complete the physical chemistry laboratory course, students must perform nine experiments in the areas of thermodynamics/heterogeneous equilibria, kinetics and electrochemistry. Each experiment consists of the hands-on performance, a brief oral examination, and a written electronic laboratory journal entry.

For each experiment, the students have an instruction at hand that they can download from the university’s learning management platform (Moodle). In addition to the instruction for an experiment, a genial.ly-based digital instruction is also available on Moodle, which mainly links photographs of the experimental setup with tasks from the instructions [15]. To further support the students, a pre-structured electronic laboratory journal entry (template) is provided for each experiment, which includes the general layout (title, sections, etc.) and a pre-structured, detailed measurement protocol. The experiment’s protocol must be written as an electronic laboratory journal entry (see Section 3.2.4). The different sections (short introduction with necessary equations, measurement protocol, discussion and short summary) in the template must be filled in by the students. The physical chemistry lab is equipped with a personal computer at each workstation where the students fill in the measurement protocol during their lab time. Afterwards, the students must evaluate the measured data and discuss them according to the given task. For data evaluation, the students are free to choose a piece of software. In this laboratory course, the students learn a more scientific documentation of experiments, which is a bit above the scope of a pupil’s experiment. Because of the good rating of the use of the laboratory journals (see Section 4.2), it can be assumed that the students will implement other forms of documentation than only protocols if they are teaching chemistry at school.

3.1.2. Reflection Tasks

The laboratory journals in the organic chemistry laboratory course contain reflection tasks [16]. The students complete sentences that begin, for example, with “Today I particularly liked the fact that …” or “Today I had to solve the following problem …” A total of eight different sentence beginnings are given. Students are asked to choose a different one each day, with two beginnings used twice because the course lasts 10 days. Kolb includes reflection as an important part of the learning cycle [17] that prepares students to learn new content. Therefore, each laboratory day ends with this reflection task. The coding of the students’ written reflections showed that the reflections focused mainly on their own practical skills. This is followed by school-related statements [16].

Reflection is a core competence of teachers [18]. The reflection tasks in the lab course can contribute to building up this competence. It also shows how students at school can reflect on their own learning process using simple approaches such as these reflection tasks. However, it should be kept in mind that reflection only adds value to the learning process if the learner has sufficient (prior) knowledge and skills [19]. By writing the reflection tasks, the pre-service chemistry teachers are in a dual role: as learners and as prospective teachers. Therefore, this learning opportunity also functions as a didactic double decker.

3.2. Digitalization

3.2.1. (Interactive) Videos

As part of the general chemistry practical course, our pre-service chemistry teachers learn working techniques that they should not only master themselves but also demonstrate and teach to their students as chemistry teachers in school. For this reason, we have created detailed videos on the most important working techniques (e.g., cleaning glassware, handling a burner, carrying out a titration), because the use of computer-aided support for laboratory lessons reduces the time needed to learn a skill and at the same time improves students’ skills [20]. The videos contain numerous tips and additional explanations on the correct use of equipment or possible sources of errors. We have enriched these videos with interactive H5P elements (e.g., different types of questions, tables, images, links and interactive summaries) so that students can keep track of the wealth of information and do not forget the content from the beginning to the end of a video. This encourages students to engage more deeply with what they see. For example, after the individual sections of a video, there are multiple-choice questions to answer or fill in the gap tasks to complete. If students answer the questions incorrectly, they can watch the previously viewed segment again. Answering the questions in the video also gives the students immediate feedback on the quality of their understanding of what they have seen so far. In addition, the videos could be viewed both at home in preparation for the laboratory practical and on tablets provided on site in the laboratory, as Cresswell et al. were able to show that it is particularly advantageous for students to watch the corresponding videos while they are preparing or carrying out the respective task [21]. Furthermore, the use of interactive videos is also a useful method for teaching chemistry at school. Another advantage of these videos is that they can be made available again in later laboratory courses, for example in inorganic chemistry or physical chemistry, so that students can use the videos to check whether they have remembered the individual steps of a titration, for example. This contributes significantly to safety when working in the laboratory.

3.2.2. Interactive Checklist for Protocols

In order to support our first semester students with the preparation of protocols and to teach them the requirements of a good protocol, we first created a checklist to help them check if all the required aspects are included or considered in the protocol they are writing. This checklist includes, for example, the item ‘Illustrations’, which states that illustrations must have meaningful captions and be numbered. Both students and examiners can check this and mark the appropriate item on the list. There are also aspects that are weighted more heavily, such as the point ‘Realization’. Students will be assessed on whether they have formulated these in their own words in a comprehensible and detailed manner (with exact concentration and quantity details, e.g., number of drops added), with deviations from a given instruction to be documented. A protocol must be revised by the student if a certain minimum number of points is not achieved.

To better support students, we also created an interactive checklist with genial.ly, as this web app has proven to be particularly effective and motivating when dealing with chemical content [22], which is especially important when it comes to the rather unpopular task of writing protocols. This interactive checklist is designed to provide concrete examples and appropriate wording for certain aspects, and students can practice outlining a suitable experimental setup or formulating an implementation step in sufficient detail using different task formats and direct feedback. Tasks have been created with genial.ly for all requirements of the checklist, helping students to create a complete protocol independently.

This interactive checklist is used in the first-year laboratory courses of the program and is rated as helpful and useful by the students (see Section 4.1).

3.2.3. Electronic Laboratory Notebooks (ELNs)

As the demand for digitalization increases, classical paper-based laboratory journals are being replaced by electronic laboratory notebooks (ELNs). An ELN has many advantages over traditional paper-based laboratory notebooks. Some of the advantages include long-term storage and availability across multiple devices [23]. They can also help to ensure good practices and to standardize workflows [24]. It is therefore a common feature of an ELN to set up databases for (experimental) protocols, laboratory equipment, chemicals, etc. Since an ELN is usually stored on a server, it is easily accessible from anywhere in the world. To respect intellectual property rights, access to ELN entries can usually be restricted. In general, ELNs facilitate collaboration because information is accessible without the need to be physically present.

A variety of ELNs are now available. The decision for a suitable ELN should be based on several aspects, such as license type, pricing, area of application, etc. An overview of current ELNs with the possibility to filter according to different aspects, resulting from a joint project of the ZB MED Information Centre for Life Science (Germany) and The University and State Library Darmstadt (Germany), is available online [25]. For a university setting, only open source ELNs were considered. The tool eLabFTW was chosen because it is a generic ELN and can be used in different research areas [26].

3.2.4. Digitalization in Data Logging

Traditionally, students in a physical or physicochemical laboratory must measure certain physical parameters such as temperature, extinction, current, potential or chemical parameters such as pH value. Very often, the measurement is performed with rather simple devices and the resulting value is entered manually into the measurement protocol. This procedure works well when the time interval between two measurements is long enough but fails when the time resolution needs to be increased, or a large number of measurements need to be recorded. When such aspects become important, automated data logging must be considered. A reason for “classical” data recording is didactic. In the “classical” way, students can easily experience the data chain from the sensing element to the instrument to the measurement protocol. Automated data acquisition carries the risk that the process itself is like a black box for students. To address this, one approach is to build data logging devices from easily accessible hardware. Therefore, we built data logging devices for our physical chemistry lab course based on an Arduino Uno. Depending on the experiment, different sensing elements are connected to the Arduino Uno and the digitized values are transferred to a personal computer. The incoming data are acquired, stored and visualized with MATLAB R2024a, a software for data analysis, algorithm development and model creation (MathWorks, Natick, MA, USA). Automated data logging allows a large number of values to be recorded and important aspects of data evaluation, such as statistical description (mean values, standard deviations, etc.) can be addressed. Subsequently, mean values as well as uncertainties for the (physico-)chemical values of interest can be calculated, which will improve and possibly widen the discussion of experimental results.

3.3. School Methods

The concept of the didactic double decker focuses on methods that students learn during their studies and then use as a teacher to teach their students. In the laboratory course, the methods that are mainly used in school are also used for teaching at university. For the students, this means that they either know the methods from their own school days, or they come to know typical school methods during their studies. Either way, the use of such methods will expand the students’ own catalog of methods.

3.3.1. Egg Race

The name of this method is primarily associated with a children’s game. Children run from one point to another while balancing an egg on a spoon without dropping it. The winner reaches the line first [27]. The method is reminiscent of the television show “the Great Egg Race”, in which participants had to solve problem-oriented physical and technical tasks in groups [28]. In learning settings, learners are given an open-ended task or problem and are divided into groups, with each group given materials with which they have to solve the task, taking into account the time available, the rules of behavior and the materials that can be used [28]. This motivating and profession-oriented method was chosen specifically for the qualitative analyses commonly used in inorganic chemistry, as these are rather unpopular with students. During the semester, students first learn the typical detection reactions for various inorganic ions in a practical course and then perform them independently on given analytical samples. To show a possible context for these detection reactions, the students perform these tests with everyday materials and food. For example, they detect nitrate in lettuce, fluoride in toothpaste, or calcium in milk or in the vegan alternative sesame seeds. Students are then presented with a realistic and profession-oriented problem in the form of an egg race, which they must solve in groups within a given time and using different detection reactions. Students work cooperatively within their group, but also in competition with other student groups. The first group to correctly solve the egg race wins a prize. For this purpose, we have created a chemical board game (based on Dobble or Spot it!) that shows both inorganic ions and images of glassware that correspond to the detection reactions to be carried out, with one copy for each group member. The compounds to be detected in the egg race were chosen to allow multiple solution paths and to require the use of different methods. This ensured that the students experimented openly.

An evaluation showed that the use of the egg race method in the inorganic chemistry laboratory course met the students’ need for more school-relevant tasks and contexts (see Section 4.2).

3.3.2. Learning Stations

Learning stations are also a method known from school teaching. The content is divided into smaller units. Students organize their own learning process independently. In the laboratory course “Organic Chemistry” of the bachelor students, learning stations with information on the laboratory techniques the students will use in the laboratory were developed and made available to the students via the Moodle course [16]. The students use the information to prepare their lab days. Therefore, this method serves as a didactic double decker. The learning stations consist of the following laboratory techniques:

• Filtration;
• Extraction;
• Recrystallisation;
• Distillation;
• Rotary evaporator;
• Analytical methods (melting point determination, refractive index, boiling point).

The stations contain drawings of the equipment setups as well as links to videos on the laboratory techniques. Students decide which information they want to write down in their laboratory journal to ensure that they are well prepared to conduct the experiment. Such a learner-centered approach can also be recommended for use at school, as school classes are very heterogeneous [29].

3.4. Profession-Orientated Tasks

In the pre-structured laboratory journals described in Section 3.1.1 and in the context of practical experiments, students in the various practical courses should repeatedly deal with work-related tasks. The spectrum ranges from the preparation of blackboard drawings for various experimental findings to the processing of questions regarding the classification of the experimental content in the school curriculum. Even in oral exams on the individual experiments, in addition to safety aspects and the theoretical background of the experiments, a school or everyday context is always discussed. In addition, there are tasks in which students are asked to put themselves in the role of a teacher and, for example, to write a fictitious letter or email to a student, asking them to explain in an understandable way some subject-specific content that the student has not fully understood. They should use both technical language and formulations appropriate to the addressee, so that the subject matter taught at the university is adapted to the level of the student’s grade. The pre-structured laboratory notebooks also include tasks that are related to the school environment. For example, one task requires students to prepare a solution of a certain concentration for a demonstration experiment at school diluting a solution of a higher concentration. When working on the task, the students not only calculate the dilution but also describe in words how they would proceed in practice to produce the desired solution.

3.5. Guided Inquiry Tasks

As chemistry teachers at school, students need to guide their students in experimentation, especially in self-directed hypothesis-based experimentation. Therefore, in the second week of the organic chemistry laboratory course, students plan experiments in small groups using a guided inquiry approach [30]. To plan the experiments, the groups receive a construction kit containing different colored cards for selecting reactants, solvents, catalysts, material, temperature and duration of the experiment, as well as cards for purification and reprocessing (see Figure 1). After selecting the cards, students use them to fill in a gapped text with the cookbook recipe for the experiment. They then check the accuracy of their instructions by comparing them to the cookbook recipe.

This method is recommended for heterogeneous groups. When planning together, group members can contribute according to their skills and knowledge. This approach is therefore also suitable for chemistry lessons at school. For experiments that allow a variety of experimental approaches, a more open-ended approach would also be possible. For the experiments in the laboratory course, this approach was not possible due to safety issues. In the next course, the pre-service chemistry teachers will receive planning cards for school experiments where they can carry out their planned experiment without checking for correctness. Here, an open inquiry approach [31] is possible and should be an even more suitable didactic double decker than the guided inquiry approach. However, this approach focusses on planning and makes transparent which planning elements are part of the planning of an organic chemistry experiment. Insight into such planning contributes to the concept “nature of science” [32] which is also important for future chemistry teachers, because their students should learn how science works and not just facts.

4. Evaluation of the Lab Courses

In recent years, the laboratory courses (all or some elements of the course) have been evaluated using qualitative and quantitative analyses. To obtain quantitative data, Likert scale questionnaires (with both four and five answer options) were used. SPSS 28.0.1.0 statistics and MS Excel software were used to analyze data, providing arithmetic means and standard deviations. Due to the small numbers of participants, no control groups could be used for this evaluation.

4.1. General Chemistry

In the practical courses of general chemistry and inorganic chemistry, the (profession-oriented) innovations (interactive checklist, egg race, etc.) were evaluated to find out from the students’ feedback to what extent they are considered helpful and to identify the need for optimization. The evaluation results of the individual measures were used as a basis for a revision and for a decision on a continuation and permanent implementation of these measures. Therefore, the students’ feedback on the interactive checklist for general chemistry and the feedback on the egg race for inorganic chemistry are presented here.

An evaluation of the interactive checklist in 2023 (N = 24) included a total of 18 five-point Likert scale questions and three open-ended questions (What suggestions for improvement, ideas or wishes do you have? What did you miss? What would you like to see in terms of interactive instructions?) Overall, the interactive checklist was rated as very helpful in communicating the applicable requirements for a protocol to students (M = 4.25). The explanations and interactive examples included in the checklist were also rated as easy to understand (M = 4.17). Most students liked the interactive checklist (M = 4.21) and the majority of respondents enjoyed working with it (M = 3.5). After completing the interactive checklist, students were also confident that they would be able to create a correct protocol (M = 3.80) and perceived an increase in their own professional competence in writing protocols (M = 3.96). The only criticism expressed in the open questions was regarding the technical availability of some tasks with a particular browser (N = 5; these problems have since been resolved). In addition, there was a wish for additional verbal explanations of the individual examples and tasks as well as the possibility of asking questions verbally (N = 1). Furthermore, one student said, ‘I liked the idea of the interactive checklist’.

4.2. Inorganic Chemistry

The egg race for qualitative analysis was conducted for the first time in the inorganic chemistry laboratory in the summer semester of 2024 (N = 20). Only closed questions with a four-item Likert scale were used for the survey. Numerous questions were used to identify potential for optimization. In addition, feedback on the method in general was obtained. The school context and the relevance of the chosen topic of the egg race for the real world were rated as high (M = 3.20), and the topic was generally perceived as very interesting or exciting (M = 3.65). All students were able to solve the given task with the help of their previous knowledge in chemistry (M = 3.85) and to relate the task to their individual previous knowledge (M = 3.40), but they could still learn something new while working on the egg race (M = 3.30). It was also recognized that there are several solutions to the egg race (M = 3.90) and that a solution to the egg race problem would not have been possible without the introductory experiments and qualitative analyses in the inorganic chemistry lab (M = 2.75). Overall, the students’ existing experimental skills were considered sufficient to confidently perform the experiments required to solve the egg race (M = 3.10). The egg race was seen as contributing to professionalization of teacher training (M = 3.50). Therefore, the egg race is now being consolidated because it is a good application for the otherwise rather unpopular qualitative inorganic analysis and, in the sense of the didactic double decker, also enables practical experience with learning objects and later the method can be used in one’s own teaching.

4.3. Organic Chemistry

During the first week, the evaluation of the laboratory course focused mainly on the acquisition of basic laboratory skills and the suitability for the future profession of the students [16]. Students rated the acquisition of practical skills positively and as suitable for application to new experiments. The suitability of the course for their future profession was also rated with a clear focus on these practical skills; students rated the course as relevant because they rated the practical skills as relevant for their work as chemistry teachers [16]. In the second week, the students’ opinion of the guided inquiry approach was also of interest [30]. For example, one student wrote “The idea of week 1 learning the methodology, week 2 applying the methodology worked really well”. The results of the questionnaire show that the students were satisfied with this second week of the laboratory course. The methodical approach of the planning phase was rated 3.79 on a 5-item Likert scale and the materials provided for this phase were rated 4.00.

4.4. Physical Chemistry

Student evaluation of the laboratory course is usually completed at the end of the laboratory course. The students (pre-service chemistry teacher, N = 14 answered, summer term 2024) were asked to give their opinion on several aspects of the laboratory course. The questionnaire consisted of some open-ended questions, questions with response options based on a four-item Likert scale (“completely agree”, “agree”, “disagree”, “completely disagree”—in a few cases with an additional option “not used”) and some multiple-choice questions. The digital instructions (made with genial.ly) were positively perceived by the students. The use was intuitive (M = 3.23, SD = 0.89), supportive of their own practical lab work (M = 3.25, SD = 0.92) and helped to better understand the experiment instructions (M = 3.33, SD = 0.62). The pre-service chemistry teachers were open to creating digital instructions themselves for their future chemistry classes (M = 3.00, SD = 0.85), which again shows the potential of the didactic double decker.

The ELN eLabFTW was not a serious obstacle in the physical chemistry laboratory course. The students stated that they could use eLabFTW quite well after a short training period (M = 3.00, SD = 1.13). In principle, the students support the use of an ELN for practical work in the laboratory and for the evaluation of experiments (M = 3.43, SD = 0.90). There was one major challenge that students experienced when working with eLabFTW. In the physical chemistry laboratory course, students work in pairs. With eLabFTW, it is (at least to our knowledge) not possible to work together on an entry at the same time as this could lead to data loss. Depending on how the pairs organized their work and whether they regularly planned to work on the same entries at the same time, this limitation caused some dissatisfaction. But, in general, the students felt confident using an ELN (M = 3.36, SD = 0.73). From a list of possible benefits (multiple choice) relating to using an electronic laboratory notebook (compared with an analogue counterpart), all students in the survey selected “location-independent access to data” as a benefit. The next benefit most students recognized was “consistent data input” (12/14), which may result from the given templates and the detailed pre-structured measurement protocols.

4.5. Research

For the evaluation, a questionnaire with a four-item Likert scale (forces choice) and open items was developed (see Supplementary Materials for all results). Nine students participated in the course during the winter term 2023–2024. During their lab course, most students stated that they learned new techniques and new technical content, were able to further develop their experimental skills, gained insight into research and learned what scientists are working on. Since these were important goals of the lab course, the students’ assessment can be seen as very positive. Most students felt comfortable during the course and enjoyed going to the lab. The items regarding the relevance of the lab course for their future profession show a very differentiated picture. One reason could be that the students were in different groups during their lab course and had different experiences. However, most of the students stated that they had improved their experimental skills, which will help them to experiment at school or to guide their future students in experiments. Here, the idea of the didactic double decker becomes very clear: own experiences while experimenting can be used to teach students at school how to experiment. They also felt that they developed their professional skills and were able to apply and connect their specialized knowledge. They rated the course as relevant to their future profession because they now felt able to make the relevance of research transparent to their students at school.

4.6. Organic Chemistry for Masters’ Students

The laboratory course was evaluated using a questionnaire with a five-point Likert scale and three open items (what I liked, what could be improved, what I wanted to say). The responses to these three items were analyzed using qualitative content analysis [33]. The results of the questionnaire are shown in

Table 3. Results of the questionnaire for winter term 2023–2024 (N = 21): M (SD).

Time frame and organization
The course was easy to complete in the time available	4.71 (0.561)
The course was generally well organized	3.86 (0.655)
We were well looked after in the lab	4.62 (0.805)
Learning effect
I have learned things in this course that inspire me	3.95 (0.740)
I took away ideas and suggestions for my future career as a teacher	4.05 (0.740)
Fitting to the module
The experiments in this course were clearly related to the lecture course	4.52 (0.512)
Overall rating
Overall, I rate the course ….	4.10 (0.436)

.

Overall, the course was rated as rather good (M = 4.10). The item that focused on the students’ future profession was also rated as rather good (M = 4.05). The students were able to take away ideas and suggestions for their future careers as chemistry teachers. The standard deviation is relatively high (SD = 0.74). Some of the students, who study biology as second subject, knew some of the experiments from other laboratory courses. This is unavoidable because biological chemistry is part of the course. Therefore, biochemical experiments (e.g., functionality of enzymes) are included in the lab course.

The responses to the open-ended questions (see

Table 4. Results for the open items.

Item	Codes	n	Example
I particularly liked this	Everyday life/school context	7	Experiments that are suitable for school and have an everyday relevance
	Atmosphere/supervision	18	Very pleasant working atmosphere
	Fit (lab with lecture course)	7	Level of the tasks, suitable for the lecture
	Analysis (own spectra)	6	I found it fascinating to hold my own spectra in my hand
	Technical skills	2	Practicing techniques from OC
	Organization	4	Good time planning
	Content	7	Revise procedures
I would still like to share this	Application	1	A lot of what I learnt in other courses was applicable and I became confident in experimenting (good repetition of various lab courses)
	Atmosphere/supervision	8	Very nice supervisor
	Variety	2	Lots of experiments that involved a lot of active work
	Other	8	Very nice ending!

) also provided interesting insights into the students’ opinions. In this course, the students very often praised the good atmosphere in the laboratory, which they attributed mainly to the good support from the supervisor. The experiments were considered as being important for everyday life and therefore suitable for school experiments. The fact that the students received NMR and IR spectra for their products was also mentioned repeatedly. For the students, this laboratory course is the last mandatory course in their chemistry studies at university. Their description of the atmosphere in the laboratory often means that they associate experimenting with a good feeling. Hopefully, this means that they will perform experiments a lot with their students at school.

5. Conclusions and Outlook

Although the sample sizes of the studies discussed above are quite small, the results are of interest in planning new or developing existing laboratory courses for pre-service chemistry teachers. As the evaluations of the laboratory courses show, most students are very satisfied with the courses and rate them as relevant to their future profession as chemistry teachers. In particular, using methods and tools the students can use for teaching is important for this evaluation. The use of such methods and tools, which then function as a didactic double decker [11], is most certainly one of the reasons why the students rate the course as relevant to their future profession. For future developments or evolution of the courses, this concept will be considered as a leading idea for planning.

The laboratory courses described and discussed in this publication were planned for a German university. The planning had to consider that due to the design of teacher studies in Germany, only limited time is available for laboratory courses. On the one hand, this can be seen as a limitation. On the other hand, the laboratory courses discussed in this paper can be seen as a blueprint for other courses as time is usually limited and must be shared between certain aspects of learning (e.g., input, exercise, consolidation, etc.).

Overall, students took advantage of the learning opportunities in their laboratory courses. For example, they experienced an increase in their own professional competence in writing protocols in general chemistry, in their skills in inquiry-based learning during the second week of the organic chemistry lab course and in their professional skills in the research laboratory courses. Contributions to their professionalization as future teachers were recognized, for example with the egg races in inorganic chemistry, for the acquisition of practical skills during organic chemistry or the introduction to electronic laboratory notebooks in physical chemistry. From all these different experiences, the future teachers can develop ideas about what to include in their future chemistry classes. Participation in the research lab courses had also an impact on their future profession. The students now feel able to make the relevance of research transparent to their students at school. In the master lab course, the students took away ideas and suggestions they can use later in school.

Although the courses are designed for pre-service chemistry teachers, all courses can be recommended for other groups. Inquiry-based learning, the use of digitalization or new methods such as the egg races can contribute to the development of experimental and professional skills regardless of the future profession of the students.