Easy Prep: Cartesian Divers

 I hear you!  More low-prep science!  You’re willing to add a few labs if they are low cost and easy to implement.  Make Cartesian Divers with a plastic bottle and a condiment packet.  Haven’t you wondered how to use that stray packet of soy sauce or ketchup?  Try making a diver with a medicine dropper, pipette and hex nut, or a pen cap.  Use a thick walled, plastic bottle—not water bottles which are easy to crush.  I find 1-2 liter bottles work well.  Fun!