Students compare the absorbency of a regular diaper and a swim diaper in fresh water and salt water. In this absorbency lesson plan, students mass the diapers and place them in water and determine the change in mass. They do the same with another set of diapers but place them in salt water. They explain the differences between the two sets of diapers. They conclude that the regular diaper gained twice as much mass because they contain super absorber polymers.