Research On Electrolyte Concept Teaching Based On TLS

Electrolyte is the core concept of senior high school chemistry,which is of great value to students in understanding solution system from microscopic perspective.Studies have shown that it is difficult to realize conceptual transformation when focusing on alternative framework,and students have the coexistence of wrong concepts and scientific concepts."Teaching-Learning Sequence"(TLS)pays attention to the stages and spiraling development of students’ learning process,and pays close attention to the interaction between teaching and learning.It is an instructional design mode that can effectively promote students’ understanding of scientific knowledge.Choosing TLS instructional design framework based on scientific epistemology can focus on students’ cognitive ways and thinking habits behind alternative framework.The purpose of this study is to develop electrolyte TLS based on scientific epistemology and carry out its teaching experiment research,so as to promote the development of students’ conceptual understanding step by step.Firstly,this study analyzes and sorts out the design framework of TLS in the existing literature,and chooses scientific epistemology as the basis of instructional design.Then,according to scientific epistemology,a TLS-based instructional design framework is constructed.Scientific epistemology holds that the construction of students’ knowledge develops in the order of "realism stage-empiricism stage-rationalism stage",and the learning situation in each stage is different: the realism stage explains concepts based on common sense,the empiricism stage obtains concepts based on perception,and the rationalism stage constructs concepts through establishing connections and scientific reasoning.TLS includes four key elements:phased teaching objectives to promote students’ knowledge construction,cognitive obstacles of students at different stages,process evaluation to grasp students’ learning situation,and intervention learning activities aimed at cognitive obstacles.TLS is a spiral ascending sequence formed by the interaction of teaching objectives,learning situation,evaluation,intervention activities and other elements.The sequence is mainly reflected in two aspects: the first is the vertical stage,which is guided and driven by the three development stages of students’ scientific epistemology,so that students’ knowledge construction can gradually realize the transition from realism stage to empiricism stage,and finally develop to rationalism stage.The second is horizontal interactivity.Under the guidance of scientific epistemology,four elements of teaching objectives,learning situation,evaluation and intervention activities are organized,which reflects the interaction between teaching and learning.According to the TLS-based instructional design framework,the TLS of electrolyte theme is designed.Under the guidance of three stages of students’ knowledge construction,the teaching objectives of rationalism stage are formulated by combining the analysis of curriculum standard requirements,textbook contents and electrolyte concept value.Combining the students’ existing experience,textbook arrangement,concept origin and development,and the survey of existing research to determine the students’ learning situation,according to different characteristics,students’ cognitive obstacles can be roughly divided into two categories: obstacle I is characterized by being subjective and naive,and obstacle Ⅱ is characterized by fixed thinking and applying rules.In order to make students’ learning situation explicit and specific,four sets of questionnaires,QA,QB,QC and QD,were developed.For different types of cognitive obstacles,design different types of intervention activities: design class I intervention activities for obstacle I-provide students with scientific facts,so that students are dissatisfied with their explanations based on common sense;Design class Ⅱ intervention activities for obstacle Ⅱ-guide students to construct thinking models,establish the connection between concepts,and break students’ original thinking set.In this study,83 students from three classes of Grade One in a school were selected as samples to implement TLS with electrolyte theme.Firstly,QA is used to test students’ previous cognitive obstacles,and the hypothesis about students’ cognitive obstacles made in this study is verified.Students’ answers constitute the analysis materials in the early stage of the study.Then carry out the intervention activities in the first and second hours of TLS,use QB and QC in this process,pay close attention to the development of students’ learning situation,and students’ answers constitute the analysis materials in the middle of the research;In the later stage of TLS,QD is used to measure students’ achievement of teaching objectives,that is,whether they have reached the rationalism stage.Students’ answers constitute the analysis materials in the later stage of the research.The four questionnaires are all composed of open questions,and the students’ answers are descriptive.The students’ answers are coded to determine the stage of students’ knowledge construction.Through data processing,the distribution of students’ knowledge construction stages before,during and after TLS and epistemological profile of electrolyte are obtained.After analyzing the characteristics of students’ knowledge construction,the following conclusions are drawn: before students participate in TLS,there are two kinds of cognitive obstacles,which hinder the development of students’ thinking mode to rationalism stage;TLS designed according to scientific epistemology can promote the development of students’ learning situation,and the students who are in the rationalism stage in the late stage of TLS occupy a dominant position;In the process of participating in TLS,students’ knowledge construction has the development sequence of "realism stage-empiricism stage-rationalism stage".In addition,this study also found unexpectedly that students’ views in constructing concepts are diversified,and for the same concept,different types of views generally exist in the minds of the same student.Finally,some suggestions on the design and implementation of TLS are put forward: from paying attention to students’ alternative framework to paying attention to students’ scientific epistemology;From denying students’ views to making use of them;Intertwine teaching dimension with epistemology dimension.The purpose of TLS design and implementation is not to replace a specific point of view about a specific concept at a certain stage,but to develop students’ scientific thinking and make rationalist way of thinking more common.The design and implementation of TLS can’t be achieved overnight,which requires the long-term cooperation and efforts of researchers and front-line teachers.