The purpose of this assessment probe is to elicit students’ ideas about the phrase conservation of matter. It is designed to find out how students interpret the word conservation in the context of matter. The probe is best used with grades 5–12. It can be extended by asking students to use conserving matter, conservation of matter, or matter is conserved in a sentence that would help someone understand what conservation means in science when referring to changes in matter. In middle and high school grades, the probe can be changed to conservation of mass. 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.