This chapter addresses the creation and use of conceptual and mathematical models, which include aspects of Developing and Using Models, Using Mathematics and Computational Thinking, and Constructing Explanations and Designing Solutions. A model is a conceptual understanding of how the universe, or some part of it, works. It provides both the foundation for understanding and a framework for making predictions about the future of the Universe. The exercise mentioned here involves asking students questions about a classroom barometer and having them sketch pictures of their working model. It gives students an opportunity to discuss differences between models and come to understand the link between the model of things they can’t see and the observation of things they can see. In this chapter, the example activity design (EAD) addresses the driving question, “Why does Earth have continents and ocean basins?” This EAD allows students to explore their mental conceptions of forces that act on a floating material and gives them an opportunity to test their model. A materials list, teacher background information, safety practices, and outcomes are provided. This book selection includes the Table of Contents, Acknowledgments, About the Authors, About the Book, Introduction, and Index.