Effectiveness of Expository-Based Instruction on Definitional Knowledge in Physical Science

This study determined the effectiveness of expository-based instruction (EBI) on the definitional knowledge in Physical Science of Grade 12 Home Economics learners at Pototan National Comprehensive High School, Iloilo, Philippines, during School Year 2026–2027. Specifically, it evaluated learners' definitional knowledge before and after the intervention and examined whether a significant difference existed between their scores. Anchored in Ausubel's Meaningful Learning Theory and Cognitive Learning Theory, the study utilized a quantitative quasi-experimental approach using a one-group pretest–posttest design. The participants consisted of 30 learners from an intact class. A researcher-made test covering eight scientific terms related to Kinematics, together with a scoring rubric, was used to measure learners' ability to define scientific concepts. The instructional intervention involved the systematic presentation and explanation of concepts, relevant examples, illustrations, and guided classroom discussions. Data were analyzed using descriptive statistics and a paired-samples t-test at the 0.05 level of significance. Results indicated that learners' mean definitional knowledge score improved from 1.00, interpreted as very low, in the pretest to 3.10, interpreted as average, in the posttest. The reported paired-samples test also showed a statistically significant difference between pretest and posttest scores, t(25) = −9.265, p < .001. These findings suggest that EBI may help improve learners' understanding and expression of scientific definitions. However, the nonappearance of a control group limits causal conclusions. The findings may notify science teaching practices and support the integration of structured explanations, examples, and illustrations into Physical Science instruction. Further studies involving larger samples and comparison groups are recommended to strengthen the evidence for the effectiveness of EBI.