Which one would hold heat better: one with insulation or one without?
First thing that comes to mind is add some dry ice to the cup with the cubeDry ice is much colder than 32 degrees f so the cube should stay frozen.
Some dry ice would do the trickWell packed sawdust might even workLiquid nitrogen may be available at your school, if it is it could certainly keep the ice cube frozenWhatever you use just be sure to close your yogurt pot.
how long for? in case you used an insulating jacket or a thermos bottle (this keeps warm issues warm and chilly issues chilly), then it may final for numerous hours - like once you wrap an insulating jacket around a wine bottle to maintain it chillydesire that facilitates :]
Ok start with a good insulator, such as polystyrene (Styrofoam), i think you can get it in pink sheets about one and a half inches thick, and make a box just big enough for the ice cube, making the walls as thick as possibleNow add a small hole to drain melted waterBecause water will increase the rate at which the remaining ice melts.
Since I live in a house that had no wall insulation when I moved in, I assure you that one with insulation holds heat (and air conditioned air) better than one withoutAlso important is to have vapor seal to keep wind from leaking air through the small gaps.
