Computers and computer algorithms have contributed to important scientific advances by allowing scientists and engineers to create and use sophisticated models to explain and predict phenomena. Yet, of the eight "Next Generation Science Standards" ("NGSS") science and engineering practices, computational thinking may be the least familiar to teachers and students. In the "Framework for K-12 Science Education" (NRC 2012) computational thinking is linked with mathematics as tools for representing variables and relationships. But what exactly computational thinking means for learning and teaching is not always clear. Does engaging in computational thinking mean students should use spreadsheet software and other computer tools to manage data? Is having students use online simulations to visualize phenomena computational thinking? Should students be writing code and building computational models? Computational thinking can mean all of these things and more. In this article the authors unpack computational thinking practices by presenting a sequence of instructional activities focusing on groundwater contamination. The instructional approach does not require coding but does support students in engaging in the computational thinking necessary to use models to understand problems that are relevant to their lives and communities.