Understanding word equations

Keith Taber and Pat Bricheno of Cambridge University have completed a study of students' understanding of chemical word equations.¹ For the study 300 secondary students had to complete five word equations where one item was omitted from each equation. They were asked to name the missing substance and explain their answers.  

Based on the results of the study, about 65 per cent of the answers provided were judged correct and 20 per cent incorrect. The other 15 per cent of responses were technically wrong but were considered to be close to the right answer. This shows that most respondents were able to offer a correct or nearly correct answer. However, if the non-responses are assumed to indicate that the student could not offer any answer, then about a quarter of possible responses were incorrect.