Editing Screaming Pennies (section)

== Why This Works ==

When the pennies are pressed into the dry ice, there are two major things at play. The first is that the dry ice is ''Sublimating'', or going from the solid state to the gas state. We know that it is already doing this while sitting out in an open room, since the room is substantially warmer than the dry ice. The second is that pennies are made of metal, and metals are ''Conductive''. In this case, we are seeing the penny conduct heat into the dry ice much faster than the air, causing the dry ice to sublimate much faster where the penny is being pressed. This means the expanding CO<sub>2</sub> below the penny has to squeeze out around it, causing it to squeak! Once the penny has cooled down to nearly the same temperature as the dry ice, it no longer is making it sublimate faster and the squeaking stops!