Research On The Junior High School Students’ Cognitive Impairment Of The Mass Conservation Law

The law of conversion of mass is the key and difficult point in the teaching of chemistry in junior high school.There are some obstacles and difficulties for students to learn the knowledge in this part.The study of the law of conversion of mass will directly influence on the follow-up study in chemistry.Therefore,it is necessary to explore the cognitive impairment of junior high school students in learning the law of conservation of mass,so that the following questions need to be clarified: What are the main aspects of cognitive impairment of students’ learning of the law of conservation of mass in junior high school? What are the degrees and manifestations of different types of cognitive impairment? What are the main causes of different types of cognitive impairment?Based on Gagne’s theory of classification of learning outcomes,this study explores 387 students from a city-level middle school,a county-town middle school and township middle school in Hebei Province by means of literature,interview and questionnaire.The conclusions are as follows:(1)As a whole,students have moderate cognitive impairment in the process of learning the law of conservation of quality;as far as the types of impairment are concerned,there is a greater degree of cognitive impairment in the dimension of cognitive strategy.The moderate degree of cognitive impairment is existed in the dimension of wisdom skill and the slight degree of cognitive impairment in that of speech information.(2)Among the ten secondary items of the research,the severity of cognitive impairment is that there is the thought-switching impairment from reaction without liquid to reactions in solutions.The heavier cognitive impairment is the obstacle of the logical thinking transformation from single substance to total quality of substance.It is the obstacle to the application migration of the law of conservation of mass.The moderate degree of cognitive impairment mainly shows in several ways: the obstacle of applying the law of conservation of mass to explain the phenomena in life and experiment、the logical thinking obstacle from the total mass of substance to that ofreactive substance、the rational thinking obstacle from the mass of substance to that of particles.The milder cognitive impairment manifests as: students’ obstacle to understand the law of conservation of mass、obstacle in thinking transformation from macro-representation to micro-representation as well as symbolic representation 、obstacle in experimental thinking from step-by-step weighing to overall weighing.The mild cognitive impairment is the obstacle in experimental thinking from open system to closed system.(3)There are significant differences among students of different types of school in the dimension of verbal information,intelligence and skill barrier and cognitive strategy barrier.(4)There are significant differences in the dimension of speech information barrier and cognitive strategy barrier between different sexes.And there is no significant difference in the dimension of intellectual skill barrier.(5)The factors influencing on the cognitive impairment of verbal information are the inadequate ability of knowledge representation and the interference of wrong preconception.The factors affecting the cognitive impairment of intelligence and skills are the limitation of students’ thinking development and cognitive level in junior high school,the influence of fixed thinking or function and the teachers’ teaching methods.The factors affecting the cognitive impairment of cognitive strategies are the lack of basic knowledge and the lack of ability to process basic factual materials by thinking.Finally,combined with the research findings,the following five perspectives are proposed to break through the teaching Suggestions of students’ cognitive impairment.They are :(1)from the perspective of problem design;(2)from the perspective of experimental design;(3)from the perspective of model construction;(4)from the perspective of historical application;(5)from the perspective of microscopic analysis.