Applications in engineering, science and technology within undergraduate programmes can be difficult for students to understand. In this paper, new results are presented which go some way to demonstrate and explain the problems faced by students in linking mathematical models to real-world applications. The study is based on student responses to multiple-choice questionnaires on mathematical modelling problems, student reflective questionnaires and subsequent interviews. The processes used by students to solve such problems are classified and links between these process levels, credit and seven other behavioural descriptors are discussed.