Open Access. The published version of this work has been reproduced here with permission of the Publications Manager, Australian Science Teachers Association. This article may be downloaded for personal use only. Permission to reproduce this article must be sought from the Australian Science Teachers Association. This article was first published in Teaching Science, 56(3): 13-18, 2010. More information about this publisher may be found at http://www.asta.edu.au/. Copyright (2010) Australian Science Teachers Association.