The aim of the study was to investigate the effect of the Common Knowledge Construction Model (CKCM) on 10th-grade students' conceptual understanding of the buoyancy and density of liquids topic. Within a pre-experimental (one group pre-test/post-test) research design, this study was conducted with 22 of 10th-grade students. To collect data, the Word Association Test (WAT) and Structural Grid (SG) were employed as pre- and post-test. Students' conceptual understanding of the states of objects in different positions (swimming, sinking, and suspending) in the liquid was determined by means of the SG. Through the WAT, the cognitive structure of the students for the stimulus words of mass, volume, density, buoyancy, and Archimedes was determined. According to the post-tests for the SG questions, it was determined that there was a significant increase in the number of correct boxes selected and a significant decrease in the number of incorrect boxes selected. In addition, it was determined that the mind map obtained from the post-WAT, which revealed the cognitive structures of the students, had a much more interrelated and complex network. The findings obtained are compared with other related studies in the literature and some suggestions for teaching science subjects of CKCM are given.