The purpose of this study was to gather information about how students learn the foundational concept of conservation of matter during a non-chemistry unit on the rock cycle. The unit covered the rock cycle, rock types, and the law of conservation of matter, and took place in a sixth grade classroom of 30 students. Students made significant learning gains from pre-test to post-test and showed mastery in less complex subject areas, but struggled to learn the more complex concept of conservation of matter. More research is needed in order to gain a greater understanding of how students learn foundational concepts such as conservation of matter, and how they are able to apply their understanding across disciplines in science. This study offers suggestions for future work including a series of questions to assess student misconceptions about matter, and how to use those questions to measure students' ability to transfer knowledge to different learning contexts.