In recent years, researchers have shown an interest in understanding students' ideas about basic chemical principles and guiding them through innovative ways to gain conceptual understanding where necessary. This research was a case study designed to assess 50 first-year high school students' conceptual understanding of changes in matter with interpretative underpinnings. A diagnostic probe was administered to find out if discrete particles could be used to differentiate chemical changes from physical changes and to unravel the different conceptual interpretations that students had. submission obtained from the students was classified on the level of conceptions and analysed using the frequency counts and percentages after which an interview was conducted to gain a deeper insight into their unscientific submission. findings from the study indicated that only a few students had difficulties in distinguishing between physical and chemical changes. these few did not associate the changes in the states with associated physical and chemical properties a was expected at their level.Ìý Neither dud they base their explanation on the breaking nor formation of bonds, nor changes in the constitution of entities. They overwhelmingly intimated that physical changes were reversible whilst chemical changes were not. About 38% of the participants who provided correct definitions for physical and chemical changes in two of the probes could not assign reasons for them. However, almost 79% of the participants showed and appreciated knowledge of the types of changes that occur in chemistry. the adopted diagnostic probe and interview were useful in identifying students' alterative conceptions about changes in chemistry, Diagnostic probes are recommended as a pre-requisite for conceptual change strategies.

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