This study explored the differences between eight-year elementary school pupils (before the curriculum reform) and nine-year elementary school pupils (soon after the curriculum reform) in Slovenia, as regards specific chemistry knowledge and motivation to learn chemistry. Altogether, 191 elementary school pupils participated in the study. The results show that pupils of nine-year elementary school are not significantly better at chemistry knowledge test scores than eight-year elementary school pupils. Similar results were obtained when comparing intrinsic motivation. The results also show that those students who exhibit a higher level of intrinsic motivation to learn chemistry do not perform better at the test as a whole, but the correlation is low, although statistically significant, between motivation and pupils’ performance at solving selected problems presented in this paper. Results show that students develop different misconceptions of selected chemical concepts. Based on the results of this study, some guidelines for teachers are suggested.