In order to develop successful teaching approaches to transformations of matter, we need to know more about how young students develop an understanding of these processes. In this longitudinal study, we followed 25 students from 7 to 13 years of age in their reasoning about transformations of matter. The questions addressed included how the students' understanding of transformations of matter changed and how we can make sense of individual learning pathways. In interviews performed once or twice every year the students described and explained three situations: fading leaves left on the ground, a burning candle, and a glass of water covered with a glass plate on which some mist had formed. When analysing the interviews, we found a common pathway of how the students' ideas changed over the years in each one of the situations. When analysing individual student's interviews with Ausubel's assimilation theory we could discern subordinate, superordinate and combinatorial learning. How these findings can contribute to an improvement of teaching about transformations of matter is discussed.