Design Challenge: Ice Cube Insulator

Credit: PBS Learning Media

Can you keep an ice cube from completely melting in 30 minutes?

Use the materials to make a Keep-a-Cube box that will keep an ice cube from melting.Think about what makes ice melt as you design your box.You can wrap up the ice cube, cover the box, or do anything else you can think of. 2 Put a second ice cube on a plate. This is your “control” cube. Don’t make any changes to this ice cube. 3 Wait 30 minutes. 4 Compare the ice cube in your Keep-a-Cube box to the ice cube on the plate.Which ice cube is bigger? Why?

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Background Reading

Heat travels in three ways: directly through matter (conduction); from object to object through a fluid medium (convection); and in waves that can carry energy across even empty space (radiation). Insulation slows heat transfer from warmer areas to cooler ones by slowing at least one, but preferably all, of these processes.

Heat conduction can be slowed with materials that are poor conductors. Plastic, paper, and wood, then, are good thermal (heat) insulators. Air is one of the best insulators, but it only works as a good thermal insulator if confined to a space small enough to prevent the circulation of convection currents. While dull black objects readily absorb and emit radiant heat, shiny silver ones tend not to. This means aluminum foil makes a good barrier to radiant heat, reflecting as much as 95 percent of the heat that reaches its surface.

To keep cold objects cold, you need to stop or at least slow the flow of heat from the outside in. To keep their ice cubes from melting, the ZOOM cast members in the video segment select what they hope are good insulating materials, like newspaper and cardboard. By suspending the ice cube, they prevent conduction from occurring between the cube and the wrapping material, and they also take advantage of the surrounding air's superior insulating properties. To minimize the effects of convection, they seal the container to stop the circulation of trapped air. And to deflect radiant heat from outside light sources, they make the outer surface highly reflective by wrapping it in aluminum foil.