A qualitative pre-/post-test case study was conducted to explore the influence of inquiry-based education in eliciting learners' understanding of the particulate nature of matter in the gaseous phase. Two grade four classes (n=116) were conveniently and purposively sampled from two farm schools in Pretoria, South Africa. Data was collected through pre-test, initial group interviews, post-test, final group interviews and field notes. The pre-intervention data indicated that the continuous, continuous-animistic and the continuous empty models of matter in the gaseous phase dominated learners' understanding in all the four classes. A considerable decrease in the continuous model was observed in the inquiry classes rather than in the lecture classes post-intervention.