This paper addresses the question of whether particle ideas help or hinder young pupils' understanding of changes of state and dissolving. Two matched groups in a primary school in Greece (ages 10/11, n = 20 and n = 19) were respectively taught one of two parallel lesson schemes. Covering the same phenomena, one scheme incorporated particle ideas, and the other did not. Data were collected pre and post intervention through individual interviews (n = 24). Results suggest that pupils' understanding benefited from the introduction of particle ideas. Implications for the primary science curriculum are discussed.