Wyniki wyszukiwania - BazTech

1

Microwave-aided reactions of aniline derivatives with formic acid : inquiry-based learning experiments

Mycak Michael, Doležal Rafael, Bílek Martin, Kolář Karel

Chemistry-Didactics-Ecology-Metrology

|

2022

|

R. 27, NR 1-2

135--151

EN

The synthesis of amides belongs to traditional experimental tasks not only in organic chemistry exercises at universities but also at chemically focused secondary schools or in special practices at general high schools. An example of such a synthesis may be the preparation of acetanilide via reaction of aniline with acetic acid or acetic anhydride. However, both of these reactions are associated with a rather long reaction time and certain hazards that limit their straightforward use in pedagogical practice. Conveniently, the reaction of aniline with acetic acid may be significantly optimised if it is performed under solvent-free conditions in the presence of microwaves, which reduces considerably the reaction time and provides very good yield, compared to traditional heating by a heating nest. In this study, the main pedagogical aim of the experimental design is elucidation of the influence of the structure of the amines on the course of the reaction with formic acid through inquiry-based learning. Specifically, the proposed experiments consist in investigation of the chemical yield achieved in microwave assisted reactions of aniline and its derivatives with formic acid in such a way that is adequate for constructive learning of undergraduate chemistry students. The selected series of amines involves aniline, 4-methoxyaniline, 4-chloroaniline, and 4-nitroaniline. In accordance with the chemical reactivity principles, students gradually realise that the influence of the substituent is reflected in the reaction yield, which grows in the following order: N-(4-nitrophenyl)formamide ˂ N-(4-chlorophenyl)formamide ˂ N-phenylformamide ˂ N-(4-methoxyphenyl)formamide. Therefore, the results of the experiments enable students to discover that stronger basicity of the amine increases the yield of the amide. In order to deepen the students’ chemical knowledge and skills, the concept of the experiments was transformed to support inquiry-based student learning. The proposed experiments are intended for experimental learning in universities educating future chemistry teachers, but they may be also utilised in the form of workshops for students at secondary schools of a general educational nature.

2

Experiments safety - the state of art at schools in Czechia

Rusek Martin, Sakhnini Sohair, Bílek Martin

Chemistry-Didactics-Ecology-Metrology

|

2022

|

R. 27, NR 1-2

153--163

EN

Chemistry experiments have been an issue of vivid discussion for more than fifty years now. Though there are many who hold a stand-offish position, there is a general notion chemistry experiments inherently belong to chemistry instruction. In this study, attention was given first to the frequency that Czech teachers at both lower and upper-secondary schools use experiments, demonstrations, laboratory work etc. A random, generalisable sample of 354 teachers filled in a questionnaire. The results showed experiments are used only seldom at lower-secondary schools and lyceums, more frequently at grammar schools, yet just “at least once a month”. Safety showed as one of the barriers. The teachers expressed general knowledge about a norm which covers the topic, however in their further responses they expressed a lack of awareness of the compounds their students are allowed to work with. These findings are a call for measures such as: developing a database of well-described procedures including safety regulation remarks or a simplified, easy to follow list of up-to-date regulations.

3

Conditions for experimental activities at elementary and high schools from chemistry teachers’ point of view

Rusek Martin, Chroustová Kateřina, Bílek Martin, Skřehot Petr A., Hon Zdeněk

Chemistry-Didactics-Ecology-Metrology

|

2020

|

R. 25, NR 1-2

93--100

EN

School experiments represent a necessary means of subject-matter presentation in chemistry education and are important for chemical (scientific) thinking. Despite being a focus of several texts, a complex view on the experimental activity in chemistry education in Czechia is missing. The results of a questionnaire survey among 466 lower-secondary, lyceum and grammar school teachers focused on types of conducted experiments, their frequency, the place they are conducted. The most frequently used chemicals and sources of inspiration are presented in the paper. The results show that despite experiments’ significant role in education, its occurrence is rather seldom and teacher’s demonstrations prevail over students’ experiments. The list of the most often used chemicals suggests the experiments are mostly focused on inorganic chemistry. These results open further questions regarding occupational safety at schools as an important factor which could also be the reason for such a low representation of experiments in Czech chemistry education.