Causal Patterns in Density: Lessons to Infuse into Density Units to Enable Deeper Understanding Causal Patterns in Density is a curriculum module of fifteen lessons that can be used as a stand-alone unit or can be infused into a broader unit on density. The lessons are designed to address a set of persistent difficulties that students have when learning about density. These difficulties stem from how students reason about the nature of cause and effect. Each of the four module sections introduces a challenge in thinking about causality that impacts students ability to deeply understand density. The sections are sequenced to build understanding. In each lesson, a background information section describes the difficulties that students typically have in learning about density and shows how the various causal understandings, if not mastered, contribute to those difficulties. Each lesson includes subject matter goals and more general goals about the nature of causality. This module is designed for middle school but can be modified for use with older and younger students. This curriculum module was designed around best practices in science education. It was developed as part of a research project called the Understandings of Consequence Project, which is supported by the National Science Foundation.