Active Learning in the Extraction of Organic Compounds: A Study of Undergraduate Chemistry Students

Abstract

This study investigates the impact of active learning on the acquisition of competencies and learning outcomes in the context of organic chemistry education. Specifically, this study focuses on the implementation of active learning in the extraction of an unknown mixture of organic compounds using acidic and basic solutions. This research is based on an “ex post facto” study involving 40 first-year undergraduate students who are pre-service chemistry teachers at a Slovak public university. This study aims to analyse students’ performance, identify common problems encountered, and assess the advantages and disadvantages of the active learning approach. The data collection instruments included a structured report on best practices in university education and a questionnaire to evaluate the experiences and assessment systems used. This study compares the effectiveness of online and face-to-face teaching methods for practical chemistry coursework. The key findings from the comparison of these methods are the differences in learning outcomes achieved, e.g., answers to tasks 2–6 from the questionnaire. Group B respondents had a higher number of correct responses and lower variability compared to Group A respondents. This difference may indicate an improvement in comprehension and effectiveness of instruction over the period. Differences in scores between the groups may be due to random variability in the composition of the groups, which we found through statistical analysis. Full-time students felt more engaged and more satisfied. More than half of the students said that they preferred face-to-face interactions to help them better understand the material. While online instruction provided greater flexibility and accessibility, students felt that they lacked hands-on interaction, which negatively impacted their acquisition of practical skills. The results indicate that active learning, particularly hands-on laboratory exercises, had a positive impact on the acquisition of professional competencies and students’ learning outcomes. This study also highlights the advantages of active learning in practical chemistry education.

1. Introduction

The success of education is influenced by a number of factors, such as the characteristics of educational institutions, the specifics of the curriculum, the structure and content of existing databases, the volume of information stored in them, and others [1]. Active learning is a pedagogical method used by teachers to engage students in the classroom, i.e., the emphasis is on student interaction with the learning content and their active participation in the learning process. It is associated with the concept of “learning by doing”, in our case, laboratory exercise. The main goal of active learning in chemistry is to encourage students to develop a deeper understanding of topics and their applications in the real world rather than simply memorising facts. This method seeks to create an environment where students not only understand what they are learning but also why it is important and how it can be applied.

Active learning methods can significantly improve students’ acquisition of practical skills; however, the question of whether these methods are equally effective in an online environment remains open. Given the growing importance of online learning in recent years, it is imperative to investigate how this form of instruction affects student outcomes when compared to traditional face-to-face tutorials. Teaching organic chemistry at university is known to be challenging, and effective methods are needed to support students in acquiring both theoretical knowledge and practical skills. This study aims to compare the effectiveness of online and face-to-face teaching methods in the context of teaching Laboratory Exercises in Organic Chemistry at a university. The main unit of analysis is the impact of these methods (online vs. face-to-face teaching) on students’ acquisition of professional competencies and learning outcomes. In this study, we focused specifically on extraction with acidic and basic solutions. The focus was on extraction and its importance in education as a tool for developing practical skills, scientific thinking, and real-world understanding of chemical concepts.

Extraction on Specific Example

According to Kustitskeja et al. [1], student retention is a significant challenge for university education institutions and should lead to the acquisition of professional knowledge. The knowledge that student teachers acquire while preparing for their profession also relates to laboratory techniques, such as extraction.

Extraction is a key tool for separating and isolating the components of mixtures, and it has many applications. Extraction is an important process in chemistry, pharmaceuticals, food and other industries that allows one substance to be separated or isolated from another by selective dissolution in different solvents. This process is of wide practical importance and can be used for a variety of purposes. The practical importance of extraction is in the following fields: pharmaceuticals (isolation of medicinal substances, vitamins, or antioxidants from natural sources), food processing (production of essential oils, flavourings, and colourings from natural raw materials—fruits, spices, or herbs), petrochemistry and refining (separation of different components of mixtures—oils, gaseous substances, or various hydrocarbons, in petroleum refining or petrochemical processes), environmental protection (removal of contaminants from water or soil, which is important for wastewater treatment or rehabilitation of contaminated areas), research and analysis (isolation and purification of substances for further analysis), metal mining (separation of precious metals from ores and minerals), industrial chemistry (extractors as part of industrial processes—production of plastics, textiles, paper, and other products where there is a need to separate, purify, or concentrate certain ingredients), cosmetics industry (isolation of plant extracts, oils, and other natural ingredients used in cosmetic products).

Solvent extraction (SE) belongs to the group of classical analytical techniques. This analytical technique is used for the extraction of inorganic compounds after complexation with organic ligands as well as for the preconcentration and separation of solutes. It can also be applied in various industries [2].

In this paper, we have focused on the analysis of a specific application of the extraction method, followed by a discussion of its advantages and limitations. Incorporating extraction into teaching enhances the learning process and is beneficial (the acquisition of skills and new knowledge) for students. The method of extraction can help pre-service teachers better understand and subsequently teach basic chemistry concepts (conservation of mass and separation methods) and the practical application of scientific procedures. Laboratory skills acquired during extraction are important not only for professional mastery of the content but also for the subsequent effective transfer of new knowledge to students. The applied method of extraction builds on the science education standards in the Innovated State educational programme [3] which emphasises teachers’ hands-on involvement in laboratory activities as a key component in building their pedagogical content knowledge.

For example, the educational standard for the subject of chemistry is oriented to the objectives and principles of science education for grade 2 (lower secondary education) primary schools [4] and secondary schools [5]. in the thematic units covering the basic concepts of chemistry (substances and their properties, chemical reactions) emphasises the need for practical experience in the laboratory for successful teaching of scientific processes and concepts, such as separation methods (extraction, filtration, distillation, crystallisation, chromatography), and investigation of solutions and chemical compounds.

Many experiments have used the separation extraction technique. Examples include extraction of plant pigments, foods, and natural products [6]. These are experiments in which the extraction method can be combined with other laboratory separation techniques such as paper chromatography. Based on this, the teacher can explain the material and extend the chemical knowledge already acquired at the lowest levels of study using organic chemistry lab experiments, deepening the understanding of acid-base reactions and topics such as chemical structure, density, and solubility [7]. The technique mastered in a simple experiment provides opportunities for students, pre-service teachers, and pupils to apply the acquired skills to other interdisciplinary fields (biology, environmental science, physics, etc.).

Extraction is an important chemical separation technique that is essential in education, especially in chemistry and laboratory research, and includes the following:

Theoretical knowledge and its application: Students learn to understand the principles of solubility, acidity, basicity, and other chemical concepts in a realistic setting. Extraction allows students to apply their theoretical knowledge of chemistry to specific experimental situations.

Skills working in the laboratory: Students learn to work in a laboratory environment, follow safe work practices, and avoid the hazards associated with handling chemicals [8]. As Yeerum et al. [9] state, part of the reason is that higher education faces additional challenges due to the lack of hands-on experiments and the increasing number of students in elementary school chemistry who are hindered in their practical skills [10].

Problem solving and logical thinking: Problem solving is part of daily activities [11]. Students have to decide what solutions to use, what concentration to use, and what procedures to choose. In the final stage, they have to consider how they will interpret the results. Extraction requires critical thinking and problem-solving skills related to working in a laboratory. Problem solving with thinking is considered one of the most important skills for successful learning in the 21st century [11].

Emphasis on experimental methods: Students learn laboratory skills, such as how to prepare samples for analysis, perform reactions, and analyse results. Extraction allows students to gain experience in experimental procedures that are key to research and scientific advancement.

Systems thinking: As per Tümay [12], in chemistry education, it is necessary to learn the subject matter in a meaningful way. Consequently, it is important to develop a framework to implement systems thinking from a chemical perspective. Systems thinking is an indispensable aspect of our discipline through a cycle of (1) modelling systems, (2) prediction, and (3) retrospection.

Research potential: Students will become familiar with research topics and applications that use extraction, which may increase their interest in further study. Extraction is used in a variety of scientific disciplines, including chemistry, biochemistry, and pharmacology.

Improving critical thinking [13]: Students will learn to consider a variety of factors (choice of solvent, reaction conditions, and separation methods) that develop their ability to think critically and solve complex problems.

Data analysis: Data analysis is responsible for examining a set of data in order to draw conclusions about the information in order to make decisions or to expand knowledge on a specific topic [14]. Students will learn to examine and interpret the results, draw conclusions, and discuss their meaning. Performing an extraction involves analysing and interpreting the data obtained. According to the Villegas-Ch. et al. [14] data analysis subjects the data to various operations in order to obtain precise conclusions that help achieve the proposed objectives.

Observation skills and their development: Students learn to observe, analyse, and interpret the results of experiments, which is a key skill in the field of scientific research. Extraction also involves the visual observation of changes in colours, phases, and patterns.

Environmental and ethical aspects: Discussions on the ethical and environmental aspects of extraction will help students understand the impact of chemical processes on the environment and society. Increases in consumption, decreases in energy resources, lack of or inability to use renewable energy resources, etc., are among the many factors that affect air quality as well as the level of civilisation in societies [15].

The paper includes a description of the extraction procedures and a discussion of the applications and advantages of this method using a specific example.. Sharing new experimental results, analysing specific applications of the method, discussing the benefits and limitations of extraction, etc. The results achieved in the educational process of pre-service chemistry teachers are compared from the pandemic period, i.e., online education, with the results achieved in face-to-face teaching for learning both chemical theory and practical work. We agree with the authors Salta, Zois, and Tsiortos [16] that the COVID-19 pandemic forced educators to change methods of teaching and learning. According to Li et al. [17], teaching driven by big data analysis and other informational technologies has become a development trend and a hot research topic in the educational information field. Familiarity with the extraction technique can provide students with practical skills that are useful not only in a scientific career but also in a broader context, and help them better understand the processes of scientific research. Descriptions of extraction procedures, discussion of the applications and advantages of this method, and concrete examples and experiments are a good basis for expanding knowledge in the field and acquiring new knowledge essential from the point of view of the educational process.

2. Materials and Methods

The methodology involved the implementation of active learning in chemistry laboratory exercises, focusing on an independent investigation, group activities, analysing results, working through the problem, reflection and discussion, and sharing results. The study also utilised a scoping review methodology, which involved a literature search and the identification of eligible studies published between 2017 and 2023. The study sample consisted of 40 students enrolled in the Department of Chemistry at a University in Slovakia, divided into two groups: Group A (2019/2020, 2020/2021) and Group B (2021/2022, 2022/2023). The students were informed of a questionnaire that was prepared in order to improve the quality of education and increase their knowledge. The data collection process included the use of a structured report on best practices in university education, interviews, and a questionnaire to assess the best practice experiences and the assessment system used. Additionally, prior to the laboratory exercises, interviews were conducted with each respondent to gather their insights and actively involve them in the exercise. We focused on the results of the interviews, which were normalised and compared to show a true knowledge acquisition comparison between the two groups and differences in the knowledge gained. The results showed that the groups were equal when comparing knowledge.

The questionnaire consisted of 7 questions, including 1 open, 3 closed, and 3 semi-open items. The closed-ended questions focused on the theoretical knowledge acquired by the students and their applications, while the semi-open and open-ended questions provided the respondents with the opportunity to express their opinions and further insights into the issues under study. This study aimed to analyse the results of the implementation of active learning in the 1st year of undergraduate students with respect to the acquisition of students’ competencies, their learning outcomes, and the advantages and disadvantages of the experiment. The data collected from the questionnaire and interviews provided valuable insights into the students’ performance and the common problems encountered during the exercise. This study also compared the evolution of online and face-to-face teaching methods for practical chemistry coursework, shedding light on the impact of the COVID-19 pandemic on laboratory teaching and learning. Learning was combined, i.e., synchronous (live exercises presented by the teacher) and asynchronous. The specific learning procedure was a laboratory exercise as an active method. This was clearly defined and planned for both the groups (A and B). Equivalent materials and activities were developed for both the groups. Both groups A (online) and B (face-to-face), were exposed to the same types of activities on the topic of extraction. Online tools were used to simulate the laboratory exercise and discussion forums. For group B (face-to-face), analogous activities were performed in the laboratory. The materials and procedures provided in face-to-face training were identical to those used online. ICT (virtual lab, video discussion) was implemented on the LMS Moodle platform for group A (online). The method of teaching in online mode was with the help of LMS Moodle and students used technical devices like computers, tablets and internet connection. For group B, similar tools were used, and students had the same opportunities to engage. The same criteria and assessment methods were used for both groups. As part of the assessment, we continuously monitored the work of the students in both groups and evaluated the effectiveness of active learning in both environments. We then collected feedback from students through a questionnaire on how the methods were perceived and what problems were encountered. To ensure the same type of active learning in both groups, the planning and implementation of activities, materials, and assessments were ensured to be identical. A consistent approach to methodology and assessment ensured that students in both settings received the same quality of education and learning opportunities.

Research problem: How does the implementation of face-to-face active learning affect the acquisition of professional competencies and learning outcomes of undergraduate students compared with online teaching in a Laboratory Exercise in Organic Chemistry?

Hypothesis: Active learning, particularly hands-on laboratory exercises in the extraction of organic compounds, leads to significant improvements in students’ professional competencies and learning outcomes compared with online learning methods.

The extraction method is widely used in scientific research, industry, and education, allowing for the separation, identification, and isolation of substances, which significantly impact various aspects of our daily lives. This study aimed to investigate the understanding of extraction with acidic solutions by students in a combined Chemistry Teacher Education programme. The study utilised a qualitative case study design, which is an empirical method that examines real-world phenomena by considering contextual conditions related to extraction. The case study design systematically explored the extraction method using a specific example to understand its characteristics, dynamics, and contexts. Scheme 1 outlines the key elements of the case study design.

According to Huesca et al. [18], using an experimental design for students in undergraduate engineering programmes, a pre-test–post-test analysis revealed that the focus groups showed significant improvement in normalised learning gain values compared to the control groups.

2.1. Research Samples

This study employed a purposive method to extract organic matter from acidic and basic solutions. Participants in the study were students enrolled in the Department of Chemistry at a University in Slovakia. The respondents consisted of 40 students, divided into two groups: Group A, comprising 20 1st-year students from the academic years 2019/2020 and 2020/2021 (A1 = A2: 20 respondents), and Group B, comprising 20 1st-year students from the academic years 2021/2022 and 2022/2023 (B1 = B2: 20 respondents). Group A students took the online course Organic Chemistry Laboratory Exercise, while Group B students took the full-time course. The students who participated in the study were prospective chemistry teachers and took the Organic Chemistry I and Organic Chemistry Seminar concurrently with the Organic Chemistry Laboratory Exercise course.

2.2. Experimental Part

Extraction with Acid and Alkaline Solutions

In this study, we present an example of an integrated laboratory exercise focused on the extraction of an unknown mixture of organic compounds (benzoic acid, β-naphthol, and p-nitroaniline) using acidic and basic solutions. The exercise consisted of the following components: Motivation—a brief introductory input, analogies, and interesting tasks T1a–1c, which the students worked on after studying the topic from the literature, followed by answering questions in the questionnaire. These sections contribute to the overall understanding of the laboratory exercise and its educational significance.

Education method: The education method aspect is based on students’ active learning in relation to a specific topic. The exercise aimed to engage students in understanding the principles of extraction, preparation of solutions, and the factors influencing the course of extraction. This method was designed to encourage students to apply theoretical knowledge to practical scenarios.

Teacher competency represents the knowledge, understanding, skills, and intellectual abilities of the teacher and students, which are essential for the successful implementation of the exercise. Therefore, teacher education plays an important role in developing teachers’ knowledge and skills related to the use of technology in the classroom [19].

Analogies help students relate theoretical concepts to real-world applications, thus making the learning process more engaging and relatable.

• T1. The students were tasked with studying extraction from the chemistry literature, focusing on the factors that affect extraction and how these factors influence the dissolution of substances in each phase.

The exercise was divided into the following parts:

• T1a. Aqueous and organic phases in the extraction and dissolution of substances in each phase.
• T1b. Separation of selected organic substances from the mixture.
• T1c. Occupational Health and Safety when working with chemicals (scalding and ingestion).

The exercise was designed to provide students with a comprehensive understanding of the extraction process and its practical applications (e.g., coffee, tea, spices in foods, oil infusions, citrus juices, extracts from herbs or flowers, juices, smoothies, fats, and oils) while also emphasising the importance of safety precautions when working with chemicals.

T1a. Aqueous and organic phases in extraction and dissolution of substances in each phase.

It is based on the distribution of solutes between two immiscible liquid phases that are in contact with each other. Briefly, SE is the two-phase distribution of the solute (X). The separation funnel contains two layers of liquid. Generally, one is the aqueous phase (A) and the other is the organic phase (B) [20]. After X is split between A and B, the extracted analyte is recovered from phase B for further procedures or analysis. According to the above theory, this partitioning can be described using the chemical equilibrium theory as follows:

$$X_A\rightleftharpoons X_B$$

(1)

If the concentration of X is constant in one phase, it will also be constant in the other phase. This relationship between the solute concentrations in the two phases leads to the formulation of the Nernst distribution law. The distribution coefficient can be described as

$$K_D={\displaystyle \frac{{\left[X\right]}_B}{{\left[X\right]}_A}}$$

(2)

where [X]_A and [X]_B denote the concentration of X in phases A and B at constant temperature. It should be noted that the rate at which equilibrium is reached does not affect the equilibrium constant. The K_D result indicates the side of the equation in which the concentration shifts to. If K_D < 1, then a smaller concentration of X is extracted from A to B. Suppose K_D > 1, then a higher concentration of X is extracted from A to B. If K_D = 1, then the concentration of X is the same in both the phases [21].

Another factor that will affect the distribution of X in phases A and B is its solubility in every phase. The ratio of the solubility of X in the two phases is approximately equal to the distribution coefficient, which means that:

$$K_D={\displaystyle \frac{{\left[X\right]}_B}{{\left[X\right]}_A}}={\displaystyle \frac{S_B}{S_A}}$$

(3)

where S_B and S_A are the solubilities of phases A and B, and based on the aforementioned information, the extract of the compound has to be extremely soluble in the organic phase and sparingly soluble in the aqueous phase in order to be extracted successfully [22].

T1b Separation of selected organic substances from the mixture.

Some organic compounds can be separated from their mixtures using acidic or basic aqueous solutions. These react with the organic compound to form its salt, which is soluble in water and insoluble in the organic solvent. Carboxylic acids and phenols dissolved in the organic phase can be separated by extraction with alkaline hydroxide solutions (5–10% NaOH and KOH solutions). Salts or phenolates are formed, which are well soluble in water. The organic solution of carboxylic acids and phenols must first be extracted with a weaker base (such as NaHCO₃), with which only the carboxylic acids react in order to separate them. Similarly, dilute HCl is used to extract basic organic compounds. The base compound (e.g., an amine) reacts with HCl to form the corresponding salt, which is soluble in water [23,24]. The chemicals used for extraction with acidic and basic solutions were the following: benzoic acid, β-naphthol, p-nitroaniline, HCl, KOH, NaHCO₃, demi water, and chloroform.

Chemicals were weighed using a balance for analytical purposes, the RADWAG Company AS 110/C/2 (Max. 110 g, Min. 10 mg, d = 0.1 mg, Libra s.r.o., Bratislava, Slovakia).

Workflow: students were given the task of separating an unknown mixture of organic substances through extraction. This unknown mixture may have contained benzoic acid, naphthalene-2-ol, and p-nitroaniline. A sample of unknown composition (0.75 g) was dissolved in chloroform (20 mL) and extracted twice with a 20% HCl solution (2 × 6 mL). After both extractions, the aqueous layers were combined in Beaker A and set aside. The organic layer was extracted twice with a 10% NaHCO₃ solution (2 × 12 mL). After both extractions, the aqueous layers were combined in Beaker B and set aside. Finally, the organic layer was extracted with 10% NaOH solution (2 × 12 mL). The aqueous layers after both extractions were combined in Beaker C and set aside.

The aqueous layers in beakers A-C were treated by neutralisation. The alkaline aqueous solutions were neutralised with 20% HCl solution and the acidic aqueous solutions were neutralised with 20% KOH solution. The pH values were tentatively determined using a pH paper. The precipitates A-C formed were filtered and then dried, and the extraction yield was determined. The organic layer was dried by standing over anhydrous Na₂SO₄ (10–15 min) and was removed by filtration (Scheme 2).

T1c Occupational Health and Safety when working with chemicals

Occupational Health and Safety (OHS) are critical for working with chemicals [25,26]. This encompasses the importance of teaching laboratory safety [27], minimising exposure risks [28], and addressing potential hazards [29]. Students are briefed on OHS in chemistry laboratories, covering safe chemical handling and the use of personal protective equipment (PPE). According to Özbakir [26], Pryor et al. [30], and Rahmi and Ramdhan [31], the implementation of an OHS management system aims to create a safe work environment, emphasising safe work principles such as proper handling, storage, and waste disposal. Specific safety precautions for chemicals used in the experiment, such as benzoic acid, beta-naphthol, p-nitroaniline, hydrochloric acid, potassium hydroxide, NaHCO₃, and chloroform, were highlighted to minimise health risks and ensure safe handling and disposal.

The following factors affecting the effectiveness of OHS implementation were included in the safe work principles: use, chemical and physical properties, hazardous reactions, physiological properties and health hazards, ventilation, proper handling, storage, first aid for ingestion, scalding and inhalation, waste and its disposal, and firefighting of chemical fires.

The students were warned about the following for the chemicals used:

Benzoic acid (benzoic acid) care should be taken when handling and avoid inhalation of aerosol or skin contact [32,33]. This includes proper methods of mixing, dissolving, or handling the substance. Benzoic acid should be stored in well-closed containers, separate from other chemicals, and protected from direct sunlight and high temperatures [34].

Beta-naphthol (beta-naphthol, para-nitroaniline) protects against some dangerous reactions such as oxidation, reactions with acids, oxidising agents and metals. Safety measures involve using appropriate personal protective equipment (PPE) when working in well-ventilated areas [35]. The physiological and health risks are skin, eye and respiratory irritation and toxic effects if it enters the body (it causes nausea, vomiting, headache, dizziness and, in more severe cases, can cause liver and kidney damage).

P-nitroaniline (para-nitroaniline) is toxic and can have negative health effects such as dermal exposure inhalation, ocular exposure, ingestion, and chronic exposure [36]. Safety precautions and the use of PPE are required when handling this substance. It is important to emphasise that the degree of toxicity and health risk depends on specific exposure conditions such as the duration, intensity and route of contact with para-nitroaniline. Para-nitroaniline (4-nitroaniline) can undergo a variety of chemical reactions due to the presence of a nitro group (NO₂) and an aromatic nucleus, such as reduction, acylation, nitration, diazotisation and copulation, oxidation, substitution reactions [35,37].

Hydrochloric acid (HCl) is a strong inorganic acid that poses risks such as skin and eye irritation, respiratory issues, and ingestion hazards [38,39]. Safety precautions include avoiding skin and eye contact, using protective equipment, and working in well-ventilated areas [39]. Proper storage, labelling, and handling of HCl [35,40] are essential to mi-nimise risks.

Potassium hydroxide (KOH) is a strong base that can cause skin, respiratory, and eye irritation [35], and it can react with acids to form salts and water. Safety measures involve using appropriate personal protective equipment (PPE), working in well-ventilated areas, and avoiding contact with sensitive metals such as aluminium or zinc.

Sodium bicarbonate (NaHCO₃) is a weak base that can react with acids to release carbon dioxide gas, causing bubbling reactions. Safety precautions include wearing protective gear, minimising inhalation of the powder, and storing NaHCO₃ in a dry, tightly sealed container. By providing this information, you can emphasise the importance of adhering to safety protocols when working with these chemicals and highlight the potential risks associated with them.

Chloroform (carbon tetrachloride, CCl₄) is known for its toxicity and potentially hazardous effects on human health (respiratory system, CNS, liver). Chloroform has been classified as a probable human carcinogen. It may have a negative effect on reproductive and developmental capacity. Chloroform is also an environmental concern [35]. It is often found in wastewater and can contribute to the formation of chlorinated organic compounds that can be toxic to aquatic organisms. It is also important to follow measures to reduce exposure to chloroform when working with it, such as working in well-ventilated areas and using protective equipment such as respirators and gloves [35].

2.3. Data Collection and Analysis

The data of the study was collected from the results of the questionnaire, which consisted of 7 questions and conducting interviews with each respondent while also having them actively participate in the exercise. The closed-ended questions (3) were related to the theoretical knowledge acquired by the students and its application. The semi-open (3) and open-ended (1) questions gave the respondents the opportunity to express their opinions or further insights and comments on the issues under study. They focused on problem solving and logical thinking. Their role was to help the respondents understand the principle and search for answers (to think more deeply about the topic of extraction). In the questionnaire, respondents answered the questions (Section 2.3.1). The items also focused on the knowledge of the respondents-pre-service chemistry teachers, after the laboratory exercise. They were oriented to the conditions affecting extraction, how they illustrate extraction in the classroom material, and their understanding of the extraction method, which involves extracting substances using acidic and basic aqueous solutions. The section also delves into the safety precautions and the importance of occupational health and safety when working with chemicals, which is crucial for laboratory exercises. It provides a thorough understanding of the safety measures and the potential hazards associated with the chemicals used in the experiment. In addition, an open-ended questionnaire covered the students’ knowledge prior to the laboratory exercise regarding the acid-base extraction of a mixture of organic compounds. In the preparatory phase, interviews were conducted with students regarding the extraction method, conditions, and applications, as well as to confirm the results from the questionnaire. The results obtained from the interviews were used as a basis to validate the questionnaire data.

2.3.1. Questions to Be Answered in the Experiment

1. Define the principle of extraction of an unknown mixture of substances with acidic and basic aqueous solutions.

• ..........................................................................................................................................................................................................................................................................................................................

2. After the equilibrium is established, two phases are formed in the separating funnel. On what basis do you determine which phase is aqueous and which phase is organic?

(a) phase densities

(b) the characteristics (sensory and olfactory) of the solvents

(c) the volumes of solvents used

(d) other..............................................................................................

3. In what possible ways can emulsions that impair/prevent separation of the layers in the extraction funnel be removed?

(a) disruption of the emulsion

(b) desalting

(c) swirling of liquids

(d) stagnation

4. How would you separate a mixture of the substances benzoic acid, β-naphthol, and 4-nitroaniline? Aqueous solutions (20% HCl, 10% NaHCO3, 10% NaOH, 20% KOH) are available. Write the corresponding equations, including the reversible reactions.

Write ways to separate.........................................................................................

List the equations..........................................................................................................

5. Identify at least 3 types of compounds that can be separated by extraction with acidic and basic solutions, i.e., for which chemicals is this method suitable:

(a) Inorganic compounds

(b) Dyes and pigments

(c) Ionic compounds with low solubility

(d) Polymeric compounds

(e) Organic acids

(f) Alkaline substances

(g) Compounds with very low concentrations

6. What safety precautions should be observed when working with acidic or basic solutions during extraction? This question could highlight the importance of safety precautions when handling chemicals. Write a minimum of 4.

• .....................................................................................................................................................................................................................................................................................................................................................................................................................................................................

7. Indicate (write) what knowledge you have gained from this laboratory exercise? (not rated)

• .............................................................................................................................................................................................................................................................................................................

3. Results and Discussion

Students began the experiment by investigating the fundamental concepts of density and solubility. The instructor provided a minimal pre-laboratory discussion to facilitate students making observations and conclusions about these extraction principles.

During the exercise, the respondents worked in pairs to solve the problem together (group activity). As per Carroll et al. [41], learning communities can provide space and structure for people to share common goals and learn together. In the field of education, goals are personal characteristics to promote in learners (children, pupils, students, adults, etc.) [42]. Learning communities promote collective learning and complex problem solving. They explored the specific task they were given in the form of an experiment (independent exploration). In this way, the respondents actively focused on finding answers and obtaining concrete results. Groups of people who share the goal of learning are considered from different perspectives [43]. According to reports by Piccinno et al. [44], “the student perception to be strongly influenced by whether the activity is offered as an obligation or as a voluntary option”.

Respondents were given an unfamiliar mixture of substances at the beginning of the laboratory exercise. This mixture consisted of benzoic acid, β-naphthol, and p-nitroaniline. In reality, they had prepared a mixture of benzoic acid and β-naphthol in a 1:1 ratio. After dissolving the unknown mixture of substances in chloroform, they observed a brown colouration of the solution. After adding a 20% aqueous HCl solution and subsequent extraction, the students observed the formation of two phases. Dilute hydrochloric acid was used to extract basic organic compounds. In our case, it was p-nitroaniline. In the second step, a 10% aqueous solution of NaHCO₃ was added to the organic phase. Sodium bicarbonate is used to obtain carboxylic acids, such as benzoic acid. Finally, extraction was carried out with a 10% aqueous NaOH solution. NaOH solution can be used to extract β-naphthol from a mixture of compounds.

Each extraction was performed two times, as it is known that repeated (multiple) extractions are more efficient than a single extraction [45,46]. As reported by Chen et al. [45] (2023) and Zhao et al. [47], the peak was reached during the third extraction (28.88%). The results showed that the yield was significantly affected by the number of extractions, as well as the interaction between the extraction time and number of extractions [45,46]. The extractions of each compound from the mixture are shown in Figure 1.

The aqueous solutions obtained after extraction were placed in beakers labelled 1–3 (Figure 2). Neutralisation with aqueous solutions of 20% HCl and KOH was carried out. After eutralization, the starting materials were recovered from the salts. This allowed the students to identify that they had only benzoic acid and β-naphthol present in their mixture. The compound p-nitroaniline was not present in the mixture of unknown substances.

Analysing the results: during the exercises, students can analyse the results obtained, compare them with theoretical assumptions, and discuss the reasons for deviations between expected and actual results.

In terms of active learning, the following applies:

• − Assigning problems or unusual situations that require chemical knowledge to solve can promote critical thinking and application of theoretical knowledge (working with problems).
• − At the end of the experiment, a discussion was held on what the students had learned, what problems had arisen, and how things could have been conducted differently (reflection with discussion).
• − Students presented their results and observations to their classmates, which encouraged communication and feedback (sharing results). The above statement agrees with the views of many authors [41,48,49].

Results of the Questionnaire (2019–2023)

Before commencing the laboratory exercise, pre-service chemistry teachers were provided with a comprehensive handout covering the general topic of extraction acid-base extraction and an assignment to practice in class to enhance their practical skills. The subject of acid-base reactions has been thoroughly addressed in seminars, which are part of the Organic Chemistry course or are offered as a separate course under the title Organic Chemistry Seminar. Our objective was to assess how students connected their acquired knowledge of “Acid-base reactions” with the practical exercise titled “Extraction of an unknown mixture of substances by acidic and basic aqueous solutions”. In this context, the enhancement of knowledge of organic chemistry is a pivotal aspect of the education of future teachers. As Conte et al. [50] assert, the implementation of more practical activities in schools leads to an increase in social-emotional competencies.

Experiment—Question 1: Students were tasked with defining the principle of extracting an unknown mixture of substances using acidic and basic aqueous solutions. This principle was correctly defined in all cases, with both groups A and B providing accurate responses.

Experiment—Question 2: Upon the establishment of equilibrium, two phases were formed in the separating funnel. Students were required to identify the basis for determining which phase was aqueous or organic. They were instructed to select all correct answers from the options provided and possibly add more answers. Responses included considerations of the different densities of the phases as well as the characteristics of the solvents used. In cases where the densities of the solvents were unknown, students also reported considerations, such as the volumes of the solvents used in the extraction process.

Educational institutions and educators often need to deal with a large number of documents, including course materials, student assignments, teaching materials, and so on [51]. As Kelley [52] notes, much of chemistry education in the period associated with the teaching of COVID-19 has been replaced by online alternatives, and this is also the case for laboratory exercises. This fact was the reason 80% of Group A respondents answered incorrectly. According to Barton et al. [53], the sudden change to online teaching in the academic years 2019/2020 and 2020/2021 primarily negatively impacted practical laboratory teaching. This was pointed out by Villegas-Ch. et al. [14], and Shukla and Verma [54], the problem with the online educational model is that although it is intended to adapt to the needs of students both in time and in education, in reality, this does not happen, and low academic effectiveness. Group B respondents answered 20% of the questions incorrectly. We agree with the results found by Simmons and Mistry [55] that in-person laboratories are more appropriate in terms of acquiring laboratory skills and applying knowledge therein. Moreover, Carroll et al. [41] describe that the learning communities (groups) are important in how they bring together teachers, students, etc., to support one another in their learning through shared knowledge and experience. Zhang et al. [51] state that the development and application of technology will bring about smarter and more efficient methods of educational management and teaching, leading to an overall improvement in the quality of educational delivery and outcomes, but this is not the case for the acquisition of laboratory skills.

Experiment—Question 3: In Question 3 of the experiment, students were asked about methods to remove emulsions formed during extraction. The most common responses included breaking of the emulsion using a glass rod or desalting. Few students mentioned simple swirling of liquids in the separating funnel or extended standing time. It was noted that both Group A and Group B respondents had performed basic operations prior to the exercise. The lack of mastery of these basic skills was evident, as only 10% of Group A respondents and 30% of Group B respondents answered correctly.

Experiment—Question 4: In Question 4, students were instructed to use the provided aqueous solutions (20% HCl, 10% NaHCO₃, 10% NaOH, 20% KOH) to separate a combination of benzoic acid, β-naphthol, and 4-nitroaniline. The students demonstrated their ability to comprehend the provided literature, with 60% of Group A and 80% of Group B respondents answering correctly and writing appropriate equations including reversible reactions (Scheme 3).

Experiment—Question 5: In Question 5, students were asked to identify three types of compounds suitable for separation by extraction with acidic and basic solutions. However, only 10% of Group A and 20% of Group B respondents answered correctly, indicating an insufficient application of theoretical knowledge in both groups.

Experiment—Question 6: In Question 6 of the experiment, participants were tasked with outlining a minimum of four safety measures to adhere to when handling acidic or basic solutions during extraction. This question aimed to underscore the critical nature of safety protocols when working with chemicals, particularly emphasising the need for heightened precautions when dealing with acidic and basic solutions due to their potential health and safety hazards. Key safety measures to be observed during the handling of acid and alkaline solutions in vapour extraction include the use of protective work gear, working in well-ventilated areas, careful handling, proper storage and labelling of chemicals, appropriate management of acid and alkaline substances, adherence to preparation procedures, familiarity with accident protocols, cautious waste handling, and correct dilution of solutions during disposal. It is imperative that respondents adhere to these precautions when working with acidic and alkaline solutions to mitigate the risk of accidents and injuries. Respondents must receive adequate training and be well-informed about all aspects of safely managing these chemicals. The ratio of correct answers was notably higher in favour of Group B respondents, affirming the significance of the practical exercise.

Experiment—Question 7: When asked what knowledge the respondents gained from the laboratory exercise on extraction, they answered that they did:

• − practical skills (handling laboratory equipment, working with tools and instruments)—it helped them learn how to plan, conduct and evaluate experiments,
• − they learned how to collect data and record observations (a key element of scientific research),
• − validate the theoretical knowledge they have acquired and link it to practice [56]),
• − they could also use knowledge from other subjects (Chemical calculations, Statistical processing of experimental data), analyse them, apply statistical methods, and draw conclusions from the results of experiments. As stated by Hsu [57], data science education from computer science and statistics departments is becoming more widely included in general education to enhance interdisciplinary and composite competencies,
• − laboratory exercises included teaching safety procedures and proper handling of chemicals,
• − working in a team, which is an important aspect of scientific work,
• − critical thinking and evaluation of evidence are also part of the laboratory exercise.

When asked what knowledge the respondents gained from the laboratory exercise, the students answered that they found the task very interesting in terms of gaining practical skills and linking theoretical knowledge with practice. It also provided them with a valuable reference for potentially streamlining the integration of multiple disciplines within a laboratory exercise, while providing flexibility for students with different chemistry education backgrounds. Before practising the task, students were not aware that it was possible to separate an organic compound from a mixture using extraction.

They also stated that, before practising the task, the students were unaware that it was possible to separate an organic compound from a mixture using extraction. At the same time, they did not understand the connection between the experimental task focusing on extraction with acid and base solutions in the laboratory exercise and the acid-base reactions taught in the seminars, i.e., the respondents were not aware of the connection between these topics. Consequently, they stressed that, after practising and consulting the tutor on the task, they understood the connections related to the extraction of organic compounds with acidic and basic solutions. According to Zhang et al. [51], traditional education systems face many challenges, one of which is the management and utilisation of educational resources. From the answers given for the item, it is clear that active participation in laboratory exercises gives the respondents the opportunity to acquire the necessary knowledge and skills.

For online teaching (2019/2020, 2020/2021), the cancellation of lab work will affect not only students’ knowledge, but also the acquisition of lab skills (

Table 1. Verifying the Active Learning model.

Questions	2019–2021 (A Group: 20 Respondents)		2021–2023 (B Group: 20 Respondents)
	True (Number of Respondents)	False (Number of Respondents)	True (Number of Respondents)	False (Number of Respondents)
1. Principle of extraction of an unknown mixture	20	0	20	0
2. What determines the aqueous and organic phases once equilibrium is reached?	4	16	16	4
3. What are the ways to remove the emulsion?	2	18	6	14
4. Separating a mixture of substances: benzoic acid, β-naphthol, 4-nitroaniline with the help of HCl, NaHCO3, NaOH, KOH and their reactions.	12	8	16	4
5. Identify three types of compounds that can be separated by extraction with acidic and basic solutions.	2	18	4	16
6. OHS when working with acidic or basic solutions during extraction.	2	18	15	5
7. Knowledge acquired.	It has not been evaluated.		It has not been evaluated.

). When evaluating the responses from the pandemic period, it is important to reflect on its medium to long-term impact, as reported by Simmons and Mistry [55]. It is important to point out that extraction with acid and base solutions in the laboratory exercise prompted extensive discussion of the chemical principles underlying the method, as reported by Ambruso and Riley [58].

The results (Table 1) indicate that Group B (2021–2023) had a higher mean of correct responses and lower variability compared to Group A (2019–2021). Analysing the results for each question, we found that there were large differences in the number of correct answers given by respondents for questions 2, 3, 4, 5 and 6. Calculated p-values from t-tests for each question showed that these questions had extremely low p-values (for questions 2, 3, 4, 6, p = 0.00; for question 5, p = 0.01). This indicates a very strong statistical significance of the differences between online and face-to-face groups. The above results support the claim that face-to-face learning in the lab has a significantly positive effect on student performance compared to the online group. For question 1, the p-value = 1.0, indicating that there was no difference between the groups in the number of correct answers to this question because all students answered correctly. Based on the results of the t-test, we can argue that the face-to-face laboratory exercise significantly improves students’ knowledge and skills compared to the online study.

The Wilcoxon test confirmed the differences between online and face-to-face instruction. For question 1 (p = 1.00), there was no difference between the online and face-to-face groups, as all students answered correctly. The p-values from the Wilcoxon test confirmed p = 0.00 for questions 2, 3, 4, and 6, and p = 0.01 for question 6. This means that face-to-face study has a positive effect on students’ performance in these questions. The results of the Wilcoxon test supported the conclusion that practical learning in the laboratory has a significant effect on student performance.

When comparing online and face-to-face active learning in the context of a laboratory, online and face-to-face approaches have advantages and disadvantages that can affect the effectiveness of learning. The key factors are face-to-face contact with the educator, hands-on experience that is important for learning, flexibility, and learning effectiveness. Online and face-to-face methods of active learning have their own specificities, and the most appropriate choice depends on the type of laboratory exercise. Consequently, available resources and student preferences also play an important role. Face-to-face lab exercises offer a more authentic hands-on experience than online exercises. Online laboratory exercises can provide greater flexibility and accessibility. Both forms can be effective if implemented properly and if students’ needs and preferences are considered.

4. Conclusions

In conclusion, integrating an active learning approach into chemistry laboratory exercises can establish a dynamic, engaging, and stimulating learning environment, enabling students to develop a deeper understanding of chemistry and its practical applications. This study makes a valuable contribution to current knowledge by addressing the problem of defining the specific content of extraction and its application. The respondents in this study were introduced to the principles of occupational health and safety, emphasising the importance of following these principles during extraction with acidic and basic aqueous solutions. The chemical experiment allowed respondents to practice the practical aspects of extraction and acquire essential laboratory skills. This study underscored the significance of the extraction method for acidic and basic solutions, offering valuable insights for future research in this area. Subsequent research could explore the impact of other factors, such as changes in the solvent pH, temperature, and pressure, on the efficiency of organic compound extraction, potentially leading to the development of more effective and sustainable extraction methods. Overall, this study has significantly contributed to a deeper understanding of the extraction principle. Following the experiment, the students completed a questionnaire to assess the knowledge they gained from practising the extraction of an unknown mixture of organic compounds using acidic and basic aqueous solutions. The findings revealed that the students initially struggled to connect their theoretical knowledge with practical applications. However, after engaging in a hands-on task and consulting with the teacher, they were able to bridge this gap and apply their knowledge effectively over time. This article provides an overview of this type of experiment and identifies its characteristics to guide chemistry teachers in utilising them more effectively. Therefore, it is crucial to conduct as many experiments as possible during chemistry teaching.