The study explored the possibilities to improve students' argumentation ability concerning factors that affect dissolving, through the implementation of two versions of a teaching scheme, with and without particle theory. The participants (age range 10-11, n = 27) belonged to two fifth-grade classes of a primary school in Northern Greece. Data were collected through an open-ended written test and a semi-structured interview targeting four of the components of an argument: Claims, data, warrants, and rebuttals, for five factors affecting the dissolving of a solid substance in water: Temperature, stirring, amount of the substance, grain size, and nature of the substance itself. Results showed an improvement concerning the structure of students' arguments, whereas improvements in content quality appeared mainly in some cases where particle theory was implemented. Study limitations and implications for science education are discussed.