This study aimed at identifying prospective chemistry teachers' misconceptions of colligative properties. In order to fulfill this aim, a diagnostic test composed of four open-ended questions was used. The test was administered to seventy-eight prospective chemistry teachers just before qualifying to teaching in secondary schools. Nine different misconceptions were identified and qualitatively discussed. The results have implications for teaching colligative properties and in general tertiary level teaching, suggesting that a substantial review of teaching strategies is needed.