“…The teaching of models and modelling is especially difficult when teachers lack pedagogical content knowledge (De Jong & Van Driel, 2001;Justi & Gilbert, 2000Zimmermann, 2000), or when textbooks and other curriculum material reinforce or introduce alternative conceptions (Fischler & Siefert, 2001). Hawkes (1996) and others (e.g., Fensham & Kass, 1988;Taber, 1995) point out that alternative conceptions in chemistry textbooks are surprisingly commonplace.…”