Mobile computing offers potential opportunities for students' learning especially when it combines a sensing device such as RFID (Radio Frequency Identification). Researchers have indicated that a key feature of in-field learning supported by mobile devices and technology is context awareness, with which context and functionality provided by the learning system are adapted to the user's situation. However, the design of context-aware mobile learning systems provides the authors with major challenges in terms of both defining use context as well as developing appropriate concepts relevant to the design of contextual information on the systems. Educators have highlighted the role of activity in science development and learning, implying that activity theory can be used to design a mobile learning environment. This paper presents the use of activity theory as a framework for describing the design of a context aware mobile learning application. A case study for the design of a mobile learning application for science learning is described using activity theory.