Using problem-based learning questions to develop high school students’ thinking capacity in teaching Organic chemistry

JOURNAL OF SCIENCE OF HNUE Vol. 57, No. 1, pp. 16-28 USING PROBLEM-BASED LEARNING QUESTIONS TO DEVELOP HIGH SCHOOL STUDENTS’ THINKING CAPACITY IN TEACHING ORGANIC CHEMISTRY Pham Thi Binh(∗) and Dang Thi Oanh Hanoi National University of Education (∗)Email: ptbinhdhsp@yahoo.com.vn Abstract. This paper discusses the use of questions of different levels in problem-based learning. We discuss the role of questions in teaching and the level of questions as presented in Bloom’s Taxonomy and we look at the construction of problematic situations in teaching Organic Chemistry. We also introduce the use of questions carrying out problem-based learning process steps and the design of problem-based learning questions in high school organic chemistry class. Keywords: Problem-based learning questions, students’ thinking capacity, Organic Chemistry. 1. Introduction As science becomes more advanced, the amount of information that can be known by humans increases vastly. Furthermore, when we learn more, previously memorized knowledge can be forgotten. What does remain is the ability to think and solve problems, which is important in one’s life and career. Teaching critical thinking gives students a key that they can use to open the door to knowledge. Problem-based learning is a complex method of teaching in which teachers pose to their students a problem that requires conflict recognition to solve. Students must learn to recognize the contradictions within the problem in order to solve that problem. This stimulates thinking. Under the guidance of the teachers, students solve the conflict by use of critical analysis which results in the students acquiring information as well as familiarity with a method that can be used to learn more in the future. This is the development of critical thinking capacity. We are interested in identifying what it is that will help teachers make use of this method of teaching in order to develop students’ critical thinking capacity. The technique that plays a pivotal role is the formulation of problem-based questions because in the teaching process teachers must refer to questions to guide of the cognitive activities of their students. The creation of a challenging question will help 16 Using problem-based learning questions to develop high school students’ thinking capacity students recognize the conflict within the question and guide them to resolve that conflict and drawing conclusions which will make them more knowledgeable. How do teachers formulate questions that will spur their students think in a pro-active way, actively participating in the process of acquiring information? 2. Content 2.1. The different levels of questions In describing cognitive ability, educator Benjamin Bloom recognized six levels of perception: knowledge, comprehension, application, analysis, synthesis and evalu- ation. Those levels have been changed slightly to knowing, understanding, applying, analyzing, evaluating and creating. The types of assessment questions according to the Bloom’s Taxonomy [3]: Knowing questions stimulate students’ memory of facts, figures, names (of people or places), definitions, laws, rules, concepts, etc. to help students revise what they have previously learned and experienced and to help teachers assess the level of remembering knowledge of their students. Understanding questions stimulate students to make connections, and link numbers, data. characteristics, etc. as they acquire new information. They help develop students’ ability to list basic elements and compare factors and events in the unit being studied. Applying questions stimulate students’ ability to apply information obtained (data, statistics, characters) and create new scenarios. This helps students under- stand concepts and laws and learn how to choose from a variety of methods to solve problems in life. Analyzing questions stimulate students’ ability to analyze problems, determine relationships, prove a point or make a conclusion. They spur students to think and become more able to recognize relationships within and between phenomena and events and to interpret and draw their own conclusions, thereby developing logical thinking. Evaluating questions stimulate students’ ability to formulate questions, give opinions and make judgments. They will attempt to understand, make judgments and evaluate ideas, events, phenomena, etc. based on the criteria given. Such ques- tions motivate students to analyze information and make value judgments. Creating questions stimulate students’ ability to synthesize, organize and re- design information, and to bring in additional information from other sources to form a new model. They encourage students to be creative in their thinking and they direct them to discover something new. If teachers use progressive questions when teaching, particularly making use of those of higher cognitive levels (the last four levels of the scale), it is very likely 17 Pham Thi Binh and Dang Thi Oanh that they can develop students’ critical thinking capacity, increase their interest in learning, help their long-term memory and understand the subject matter better. This means improved quality of teaching. 2.2. Asking questions in problem-based learning The process of problem-based learning includes the following steps [1, 2]: Step 1 : Identifying problems, building recognition problems (creating a prob- lematic situation, identifying problems and communicating problems). Step 2 : Solving problems (setting a hypotheses to explain the problematic situation, planning and implementing a means to solve problem, identifying the correct hypothesis). Step 3 : Conclusion and application. In order to use problem-based learning, it is important to choose the con- tent within which the problem scenarios are set. There are many definitions for a problematic situation, but all of them have the following common features: they contain conflicting perceptions and stimulate learning and thinking. Thus, we find that problematic situations occurs only when an individual has a goal to reach and has neither identified a specific solution to reach the goal nor acquired the means (knowledge, skills, etc.) to achieve it. Problematic situations need to be checked against three criteria: cognitive conflict, the creation of cognitive desire and the level of student ability. The information content used in a problematic situation needs to have within it a conflict (usually an appearance of such) which can be understood by the students, or there needs to appear to be more than one possible solution, and there could be a need to explain the cause of the problem. In this paper we present the analysis of selected contents in Organic Chemistry which can be used to create problematic situations and also used to establish a method to raise questions in the steps. 2.2.1. A conflict situation with the existing knowledge of students * Content In the teaching of Organic Chemistry, problematic situations can be created when students study new substances that have structures similar to those already known. Students can predict their properties by comparing them with substances those which they studied, while in fact they do not have those properties due to differing structural features. They also can be created when students study special properties of a substance of a known homologous series. Conflict can then be created between existing knowledge and new information. Some examples are the following: - The substitution reaction of the benzene ring: Students know that a benzene 18 Using problem-based learning questions to develop high school students’ thinking capacity ring contains three conjugated double bonds and they can deduce that benzene and other members of that homologous series react in a way which is similar to that of alkenes and alkadienes. However, this deduction contradicts the fact that benzene rings readily undergo substitution reactions and they do not readily undergo addition reactions - the aromatic properties of a benzene ring. - A characteristic of multi-functional group alcohols: After learning about a single functional group alcohol, students know that the –OH group in an alcohol is a very weak acid which will only react with an alkali metal, and it will not react with a base. Therefore, when studying the reaction between glycerol and Cu(OH)2, students predict that no chemical reaction will occur. This contradicts the fact that glycerol dissolves Cu(OH)2 to form a deep blue solution. From this observation can be seen a property of multi-functional group alcohol with adjacent –OH groups. - The reaction of phenol with NaOH solution and bromine water: Phenol has the same –OH group as alcohol but its solubility in NaOH solution conflicts with the known property of the –OH group in alcohols that was learned. That phenol undergoes a substitution of three brome atoms in the reaction with a solution of Br2 conflicts with prior knowledge of the bromine substitution reaction in benzene rings (in conditions of Br2/Fe catalyst, t◦). - The week basic property of aniline: A solution of aniline does not change the color of red litmus paper and this contradicts common knowledge about this property of bases. The difference is due to the uncombined electron pair of the –NH2 group. - The mirror silver test reaction and oxidation by Cu(OH)2/OH − of fructose: The fact that fructose undergoes the mirror silver test reaction to form a Cu2O precipitate with Cu(OH)2/OH− is inconsistent with the structure of fructose in that there is no –CHO group. * Formulating questions - Introduction (building a recognition problem) + Teachers raise knowing questions or understanding questions to help their students recall what they have already learned about the properties of substances with similar structural features and the cause of those properties (or the general properties of the studied homologous series). + Teachers raise understanding questions, applying questions or evaluating questions to encourage students to compare the structure of new substances being studied and learned substances in order to predict properties of new substances (properties similar to those of studied substances). + Teachers raise analyzing questions or comparing questions to encourage a comparison of factual phenomena or data with predictions of the students – in order to detect inconsistencies. + Teachers build problematic situation. 19 Pham Thi Binh and Dang Thi Oanh - Solving a problem + Teachers formulate analyzing questions and evaluating questions to encour- age students to offer different hypotheses, suggest solutions, suggest solutions and validate the correct hypothesis. - Conclusion and application + Teachers ask students to draw conclusions (analyzing questions). + Application (applying questions). The act of creating this kind of conflict arouses curiosity and causes surprise, it makes for more exciting lessons, it stimulates thinking, it becomes an exploration of learning and it activates the desire in students to enquire. In addition, it encourages them to reflect on information previously acquired and through solving the conflict students will acquire new knowledge and a deeper understanding of the relationship between structure and properties as well as the interactions that occur between different compositions of organic compounds molecules. This is extremely important in teaching and learning Organic Chemistry. 2.2.2. Multiple choice situations *Content When learning about the structure of a substance or the chemical properties of an organic substance due to isomerism and the multi-dimensional aspect of an organic chemical reaction, students need to think carefully before choosing what they think is the correct formula of the organic substance or the main tendency of an organic reaction. Example: The situation in which the main product needs to be identified while studying the following reactions: - Substitution of halogens with different positions of H atoms in alkenes; - Substitution of the asymmetrical atoms into positions next to the asymmet- rical C=C bond (Markonicov’s rule); - Substitution of the benzene ring when there is a side group; - Removal of HX in dehalogenation and H2O from alcohol (Zaitsev’s rule). * Making questions - Background (building a recognition problem): + Teachers raise applying questions: write different structural formulae hav- ing the same molecular formula or different products of a reaction based on the properties of that reaction. + Teachers raise evaluating questions: construct a conflict situation by asking what the main product will be. - Solving problem: Having given the factual phenomena to students, teachers raise analyzing ques- 20 Using problem-based learning questions to develop high school students’ thinking capacity tions to let their students draw their own conclusions or raise analyzing questions based on the mechanism of the reaction so that the students can deduce the main product. - Conclusion and application: + Conclusion (analyzing questions). + Application (applying questions). With this kind of problematic situation, students can see clearly the multi- directional property of an organic chemical reaction and also realize that human beings have the capacity to be knowledgeable and control the tendency of many reactions as they wish. 2.2.3. Cause-and-effect situations Cause-and-effect situations which need some explanation are created when students need to find a way to apply what they have learned to the reality that they observe. This helps them find the answer to a ‘why’ question or the cause of an effect. While teaching Organic Chemistry, we often encounter problematic situations because students need to understand the relationship between structure and prop- erties and the interaction between the different adjacent groups in the same organic molecule. With problematic situations as presented in section 2.2.1, 2.2.2., situations can be created which need an explanation as to the cause. The main objective of teaching is to help students find the cause to a phenomenon, and a certain property of a substance, or to combine one problematic situation with the remaining two types of problematic situations when teaching (in reality this problematic situation is often combined with the remaining two situations). Example: - While teaching Markonicov’s Law, students need to learn about the ten- dency for a certain main product to form during an addition reaction and they need to understand the cause of this tendency. Teachers that ask them to write an addition reaction between acids or water and diastereomer alkenes will create a choice situation where the main product needs to be determined. This problem can be solved using actual data and numbers. After that, students need to answer the ‘why’ question - to explain the rationale behind that law. - When teaching the properties of complex alcohols: initially a paradox dead- lock problematic situation occurs when glycerol contains an –OH group of alcohols (with very weak alkali characteristics) but is able to dissolve base Cu(OH)2. Raise a cause-and-effect question or a ‘why’ question. To answer such a question, students will need to understand that though it is true that –OH is very weak in its alkali characteristics, the reaction with Cu(OH)2 is not simply an acid-base reaction but is an electrophilic reaction due to the presence of the adjacent –OH groups for easy 21 Pham Thi Binh and Dang Thi Oanh giving and receiving, and the proximity of many –OH groups also causes H(–OH) group to be more mobile. Therefore the same functional group can have different properties if there is more than one of them. With this type of problematic situation, students will understand the nature of organic chemical reactions, the relationship between structure and properties, the effect that different parts of the structure in the molecule have on the others, and as a result will be able to remember easily and apply this information in other situations. 2.3. Design questions in problem-based learning for some spe- cific content in Organic Chemistry in High schools * Example 1. The properties of multi-functional group alcohol (specific re- actions of glycerol) in unit 54, Advanced Chemistry 11 After teaching about the properties of single-functional group alcohol, teachers create a transition: So, the –OH group is a very weak acid, weaker than H2O, and it will only react with alkali metals. - So what will be observed when a solution of either ethyl or glycerol is added to test tubes containing Cu(OH)2? - Now let us conduct the experiment and you observe and explain to me the reason for this phenomenon. (Teachers conduct two experiments: glycerol and ethyl with Cu(OH)2). - From the observation of the reaction, speak about the capacity of alcohols to react with Cu(OH)2. - Why does glycerol react with Cu(OH)2 while ethyl does not react though both contains –OH group? (hint: What is the difference in structure between these alcohols?) Teachers explain, give the formulae of the products of the reaction. - What can we conclude about the reaction between alcohols and Cu(OH)2? - Which of the following alcohols dissolve Cu(OH)2 forming a dark blue solu- tion? A. ancol propylic B. ancol etylenglicol C. propane-1,3-diol D. butane-1,4-diol. Write the chemical equations to show what occurs. * Example 2. The chemical properties of fructose (transformation in alkaline medium) in unit 5, Advanced Chemistry 12 - From the structural formula of fructose, make predictions on its chemical properties. (Fructose has properties of both multi-functional group alcohols and ketones). 22 Using problem-based learning questions to develop high school students’ thinking capacity - What phenomenon occurs when for fructose reacts with Cu(OH)2/NaOH? (Cu(OH)2 dissolves creating a clear, deep blue solution). - What is the appearance of this phenomenon like? You observe the actual phenomenon when conducting this experiment. - State what was observed when viewing the reaction. (Cu(OH)2 dissolves creating a dark blue solution, then a brick-red precipitate appears). - How is this phenomenon different from what was predicted? Does this phe- nomenon suggest anything? (Hint: is the phenomenon of a reaction with Cu(OH)2 which produces brick-red precipitate characteristic of any functional group?). The brick-red precipitate is characteristic of an aldehyde group reaction. Teachers give more hints, for example, that fructose also gives a positive observation in the silver mirror test. - The fructose structure does not contain a –CHO group, so why does its reaction with Cu(OH)2 and the silver mirror test reactions show the characteristic observation for this functional group? (Hint: compare the difference between the environments of the solution of fructose in two cases). Teacher explains that in an alkaline environment, fructose can be converted into glucose and therefore fructose has the properties of a –CHO group in the alkaline environment. - What conclusions can be drawn about the chemical properties of fructose? - Can the following chemicals be used to identify glucose and fructose? A. [Ag(NH3)2]OH B. Cu(OH)2 C. Na D. Bromine water. * Example 3. Direction of the addition reaction of acid and water with alkenes (Markonicov’s rule) in unit 40, Advanced Chemistry 11 - Write the chemical equations for the reaction of propene with HCl and H2O. (Have the two products for each case). - Compare the products of addition reactions with acids and water with Ethene and propene. (Remark: asymmetric alkenes in addition reaction with asymmetric molecules