Peter Thomas, age 11, of Altoona, Pa., for has questions

How cold is dry ice ?

Dry ice, of course, is frozen gas. When carbon dioxide is reduced to a temperature of minus 112 degrees Fahrenheit, it freezes solid. That is 144 degrees Fahrenheit below the freezing point of water,

Carbon dioxide is the gas we breath out, and in its solid form it is often used in place of plain ordinary frozen water ice, When it melts back to gaseous state, it does not flow away as water. It simply boils off into the air as an invisible gas. What's more, being so much colder than ordinary ice, it is not needed in such large quantities to keep things cool.

Dry ice, however, is by no means easy to make. The carbon dioxide gas must be treated under low pressure and reduced to very low temperatures,  dry ice is more dangerous to handle thin is ordinary ice. The bitter cold stuff can give you a frost bite if you touch it to your skin.