Open Access. The author accepted manuscript version of this work has been reproduced here according to the publishers archiving policies.
This article may be downloaded for personal use only. Permission to reproduce this article must be sought from Taylor & Francis. This is an author's accepted manuscript version of an article published in the International Journal of Science Education, 33(9): 1273–1288, 2011. More information about this journal may be available at http://www.tandfonline.com/loi/tsed20
Copyright (2011) Taylor & Francis
International Journal of Science Education, 33(9): 1273–1288