Thirty-six pupils from three sixth-grade classes (ages 11/12, n = 75) in Greece were interviewed pre- and post-intervention in a piece of research on explanations of chemical phenomena. Software concerning chemical phenomena was incorporated in a teaching scheme, where the particle theory was used. After a 13 hour intervention, pupils' explanations were categorized in five discrete categories. Only a few pupils could give satisfactory explanations, involving the integration of particle ideas at the level of atoms. The idea of chemical change seemed to be very difficult for the majority of pupils. Implications for the teaching of chemical phenomena at young ages are discussed. (Contains 5 tables and 1 figure.)