The purpose of this assessment probe is to elicit students’ ideas about substances. The probe is designed to determine whether students distinguish between the everyday use of the word substance and how chemists use the word to refer to matter with a definite chemical composition throughout. It is best used with students in grades 6–12, after they are familiar with atoms, elements, compounds, and mixtures. 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.