In our Introductory Physics for Life Scientists (IPLS) course at the University of Maryland, we are building interdisciplinary bridges that help students better understand thermodynamics. One aspect of this endeavor involves having students grapple with the physical processes underlying heuristic rules that they bring to our course from their biology and chemistry classes. In particular, we have implemented a series of activities and problems intended to unpack the hydrophobicity of oil, a key step in understanding the formation of cell membranes. The spontaneous separation of oil and water is predicted by the common rule of thumb, "like dissolves like," but understanding where this comes from requires careful consideration of energetic and entropic effects. The rule must also be reconciled with the seemingly contradictory physical principle that opposite electric charges attract. This paper describes how holding up a heuristic that students have encountered in their biology and chemistry courses alongside physical principles can prompt students to look for interdisciplinary reconciliation among concepts that they previously did not even see as related. We view this as an important step toward a less fragmented experience for science students.