With recent curricular movements aimed at engaging students in science practices, more work is needed regarding evidence-based approaches for supporting students in developing competency in contexts such as chemistry. In this work, we focus on student engagement in constructing models related to graphical representations of reaction rate. Using semistructured interviews, 15 general chemistry students were provided a prompt that asked them to draw a graph to indicate how rate would change over time. Analysis involved characterizing the models students constructed, with students combining chemistry principles with mathematical reasoning to justify the specific shape of the graph. Results indicate similar chemistry and mathematical ideas discussed among the students but a variety of distinct models to describe reaction rate. The similar chemistry and mathematics ideas used by the students indicate they have productive ideas for reasoning about the context, but they need more support regarding how to combine these ideas, reflecting students' difficulty in using mathematics to model chemistry phenomena.