The purpose of this assessment probe is to elicit students’ ideas about the particle model of matter. The probe is designed to find out if students recognize that air is made up of particles that are widely spaced with empty space between the particles. Students are shown models of air inside a sealed jar and asked to choose a model or draw a different one. The probe is provided in English and Spanish. A materials list, teacher notes, standards, assessment, and references are provided. This book selection also includes the Table of Contents, Preface, Acknowledgments, Dedication, About the Authors, Introduction, and Index.