This study explores the effectiveness of conceptual change oriented instruction and standard science instruction and contribution of logical thinking ability on seventh grade students' understanding of heat and temperature concepts. Misconceptions related to heat and temperature concepts were determined by related literature on this subject. Subsequently, the Heat and Temperature Concepts Test (HTCT) was developed. The study involved a total of 74 seventh grade students in two classes. 38 students were taught by means of conceptual change oriented instruction, and 36 students in a control group followed standard science instruction. Both groups received identical instruction and laboratory experiments, however the experimental group followed conceptual change conditions while doing experiments. Prior to instruction, students in both groups were pre-tested in order to determine their understanding of heat and temperature at the beginning of instruction. Students taught by means of conceptual change oriented instruction outperformed students who received traditionally designed instruction. Results indicated that students' logical thinking ability accounted for a significant variation in heat and temperature concepts achievement. Appended are: (1) List of Common Student Misconceptions Probed by HTCT; and (2) Example items from heat and temperature concepts test. (Contains 2 tables and 1 footnote.)