Much research has been carried out on how students solve algorithmic and structured problems in chemistry. This study is concerned with how students solve open-ended, ill-defined problems in chemistry. Over 200 undergraduate chemistry students solved a number of open-ended problem in groups and individually. The three cognitive variables of working memory, M capacity and field dependence-independence were measured. A pre and post activity attitudes questionnaire was administered. The results show that there is a difference between the cognitive variables required for success in traditional algorithmic problems and open-ended problems. The context-rich open-ended problems significantly shifted students' attitudes towards problem solving. (Contains 2 tables and 7 figures.)