Slime, Slime, Everywhere is Slime
Styrofoam will melt into separate long strings when put in acetone. The packing peanuts in your kit are made of styrofoam.
60 mL acetone
Affiliate links to chemicals.
*Note: Acetone can be purchased locally as nail polish remover at big box stores. To get a big can of it, to go a home improvement store.
The Science Behind the Reaction
Packing peanuts, like the ones found in your kit, are actually made up of long strings. You can see these molecules clearly when they are broken down by acetone.
ADULTS ONLY: Let the mixture dry out a bit and mold it into a long tube. Light one end and watch the flames go!