Current U.S. science education reform efforts call for engineering to be included as part of science instruction at all grade levels. As students experience engineering instruction alongside science, an important question is how students conceptualize the nature of those two fields, and especially the extent to which they differentiate science and engineering. In this study, grades 3-5 students in thirteen classrooms participated in engineering activities as part of their science instruction for a 16- week semester. During that semester, students also interacted with an engineering graduate student who regularly visited the classroom to plan and implement science and engineering activities. Before and after that semester, we analyzed students' responses on the Draw-A-Scientist Test and the Draw-An-Engineer Test. Unlike prior analyses of those instruments, our approach focused on the alignment of students' drawings with the activities and processes of professionals in those two fields. At the time of the pretest, students' representations of scientists and engineers were often misaligned with the targeted fields, and overall alignment improved modestly from pretest to posttest. An important question was whether students would conflate the fields of science and engineering, especially after experiencing engineering as part of their science instruction. Although some evidence of conflation exists, we did not find an increased prevalence of conflated drawings from pretest to posttest. The results indicate that the inclusion of engineering activities in the science classroom does not necessarily lead students to confuse science with engineering, but also that significant work needs to be done to help students accurately conceptualize the nature of work in those fields.