Learn more physics!
How do you biuld a box that keeps an ice cube from melting
To keep an ice cube from melting you would need to completely separate
it from its surrounding, thereby not allowing any thermal conduction.
The best way to do this is to encase it in a material the has very low
thermal conduction. Styrofoam is a very good thermal insulator, however
it's not perfect so eventually the ice cube would melt (unless the
temperature outside the styrofoam container is less than the freezing
point of water).
(republished on 07/25/06)
Follow-Up #1: followup on styrofoam
Can styrofoam be a thermal insulator for warm water?
(published on 09/25/06)
Follow-up on this answer.