Teaching the law of conservation of mass to young students can be challenging. With these highly modeled worksheets, your students can understand the material better! There is also a sheet for a mini investigation where students will use pan balances to measure the mass of a box containing small items. Then they will measure the mass of each item individually. I purchase my boxes from The Dollar Tree (because I teach this skill around Halloween, I use the boxes with spooky characters on them). I then fill the boxes with small items found in my classroom. (Examples: dominoes, marbles, glue stick, erasers, etc.).