Construction Of Chemical Concept Based On Real Experiment ——Taking Catalyst And Column Chromatography As An Example

Chemistry is a subject based on experiment.Chemical experiment is not only the content of chemistry learning,but also the means of chemistry learning.The chemistry curriculum standard of senior high school(2017 edition,2020 Revision)points out that chemical experiment is the basic method to study chemical changes and an important way of scientific inquiry.It can be seen that chemical experiment plays an important role in chemical education and teaching.The research on chemical experiment mainly focuses on the use of other technologies or means to replace the real chemical experiment in teaching;Improve the existing chemical experiment scheme to enhance the ornamental of chemical experiment.The research on the correct meaning construction of chemical reconstruction in real chemical experiments has not received enough attention.We systematically study the role of real chemical experiment on students'chemical concept construction.Its work mainly includes:The related concepts are defined.The real chemical experiment referred to in this paper includes:1)experimental operation with experimental instruments and drugs on the teaching site;2)The information presented in the experiment is well matched with the connotation of the constructed concept,which has two basic characteristics.Experiments that do not meet these two characteristics do not belong to real chemical experiments,such as experimental video,teacher language description experiment,operation error or incomplete presentation information experiment.This paper analyzes the connotation of"catalyst"and its related concepts in junior middle school chemistry,and improves and optimizes the experiment"the role of Mn O₂ in the reaction of decomposition to O₂"on the basis of the textbook experiment.Mainly on the basis of the original experiment,1)by adjusting the p H value of 30%H₂O₂ solution,the substance has an appropriate O₂ decomposition rate when Mn O₂ is not added,and can collect O₂ and reburn with wooden strips with Mars,It is used to show that H₂O₂is produced without the action of Mn O₂;Combined with the acceleration of O₂ production after the addition of Mn O₂,it is used to construct the core connotation that the catalyst only changes the speed of the reaction and does not change the direction of the reaction;2)The method of wrapping Mn O₂ with filter paper objectively shows that the quality of Mn O₂ before and after reaction has not changed;The chemical properties of Mn O₂ before and after reaction remain unchanged,and the method of textbook experiment is adopted.The separation principle of"column chromatography"in high school chemistry and the Rf value characterizing the degree of separation.The conditions of the experiment of separating spinach pigment with chalk were optimized,mainly including:closed development,sampling on the chalk,optimization of the development agent system and pretreatment of spinach extract,so that the spinach pigment showed a 5-tone clear color band on the chalk.It is used to construct relevant concepts.Under the guidance of constructivism and other classroom education and teaching theories,relying on textbook experiments and improved experiments after optimization,the research of teaching design is carried out;The same content adopts two methods to design teaching cases.The difference between the two teaching cases only lies in the difference of the experimental scheme.Its goal is to study whether the improved experimental teaching scheme has an advantage in students'concept of forming the correct meaning and whether the meaning of forming the concept is correct.This paper makes an empirical study on the designed teaching plan in two parallel junior three classes and two senior two classes of Mianyang Puming middle school.In the pre-test,it is found that the learning levels of the students in the two junior three classes are basically similar,and the levels of the two senior two classes are also basically similar.In the post-test after class,it shows that the class adopting the optimized experimental scheme performs better.In the third grade,the experimental class can clearly know the three core elements of the concept of catalyst-the change speed of catalyst does not change the direction,the quality before and after the reaction remains unchanged,and the chemical properties before and after the reaction remain unchanged.In grade two of senior high school,the experimental class has a clear understanding of the mobile phase in the principle of column chromatography and its effect on compounds,the effect of fixed relative compounds and the influence of closed environment on pigment separation.At the same time,the Rf value can be displayed by graphic method.Classroom observation shows that the students in the experimental class have a higher capture of chemical experiment information than those in the ordinary class.In the process of the experiment,they can predict the results according to the experimental phenomena,and the prediction presents a strong logical relationship.It was found that the students with poor pre-test scores and good post-test scores indicated that there was corresponding phenomenon support in the experiment,which enhanced the ability of concept recognition and memory;For students with good pre-test scores and poor post-test scores,the in-depth interview showed that the experiment failed and some key information was missing,causing students to form misconceptions and doubt their previous correct judgment.Through this study,we find that the real chemical experiment can logically present all kinds of chemical information,in the failed chemical experiment,students form wrong concepts or misconceptions due to the lack of some chemical information.The problems in the research are mainly reflected in that the sample number of classroom empirical research is not representative enough,only four classes in a region are studied.