One of my favorite units of study is Fossils! The kids love doing hands-on labs and these are a lot of fun. In this one, students use a packing peanut and some wooden toothpicks to make a creature. The place their creature into the container of sand and then add water. We leave them for a few minutes and SURPRISE...the packing peanut (soft parts of the creature) dissolves away leaving the wooden toothpicks (the hard parts of the creature) not like they looked before (thanks to settling of the water and sand). Students also need to know that in the real world, this process takes a LONG time.
This lab is one of my favorites. Grab it here for just $2!