Practice And Teaching Design Of High School Chemistry Problem-Based-Learning （PBL） Based On Model Cognition ——Study As “Important Elements Sodium And Chlorine In Seawater”

Nowadays,more and more attentions are paid in the field of education to the structured design of teaching content,which can stimulate students’ interest in learning,promote the transformation of students’ learning styles and improve their problem-solving ability.Problem-based Learning（PBL）teaching mode,which aims at improving students’ problem-solving ability,has attracted widespread attention and application.The model cognitive literacy proposed in the National Curriculum Standards（2017 edition）belongs to the thinking core of the literacy of chemistry,and reflects the thinking method of chemistry.Based on model cognition,this paper uses PBL teaching mode to improve students’ comprehensive ability of thinking and solving chemical problems,to achieve the cultivation of chemical core literacy.This paper reviews and summarizes the current research status of PBL teaching mode and model cognition by literature research method,to better understand its development trend.Guided by constructivism,and The Structure of Observed Learning Outcome（SOLO）classification theory,PBL teaching mode based on model cognition is constructed.The teaching design of typical metallic element sodium and nonmetallic element chlorine is carried out based on this model,and the chemical models of "material transformation","gas preparation" and "ion test" are put forward.Two parallel classes in high school freshman were selected to carry out practical research on this model.The results of teaching implementation were analyzed by questionnaire survey and experiment method,and the results were analyzed and statistically analyzed by SPSS25 data analysis software.The research results show that PBL teaching mode based on model cognition improves students’ performance,and can promote students’ model cognition ability,independent learning ability,group cooperation ability and problem solved ability to a certain extent,which is conducive to students’ understanding,mastery,integration and application of knowledge.PBL teaching mode based on model cognition provides a useful and effective teaching mode for teachers,and promotes the transformation of teaching and learning modes.