This is a unit for students to discover what conservation of mass is all about. The students have the opportunity to learn the difference between and an open and a closed system. The main goal of the unit is for students to be able to prove that matter is never destroyed nor created, which is the conservation of matter. Students will experience multiple experiments and be able to explore how they can change and even design an experiment of their own. This unit is designed as a three-day lesson sequence, but one should note that each lesson is approximately 1 hour and 15- 30 minutes. We teach science to twice a week for longer blocks of time. If your allotted time for science is shorter than this you should try to break the lessons into shorter lessons over a longer period of time. The lessons will take about an hour and 30 minutes. Up to this point, the students have spent the last five weeks learning about matter. We have gone over states of matter, measuring matter, properties of matter, the periodic table, atoms/molecules/compounds, mixtures, solutions, physical change, and chemical change. It is important that your students have a lead up of matter to the following lessons, as they are quite complex. Students need to know enough about matter to have some background knowledge before starting this unit. There are also two additional writing prompts included to assess what your students have learned at the end of the unit. These aren’t included in the three-day lesson sequence but are great individual summative assessments if you have time. es.