Kathy Sowers, age 10, of West Allis, Wisconsin, for her question:

Why does dry ice burn?

Actually, dry ice does not burn. Yet when you touch it, the stinging pain feels like a burn and the damage it causes also looks and heals like burned flesh. The damage is really an intense type of frost bite, caused by something too cold for human flesh to endure. The temperature of ordinary ice is 0 degrees centigrade and even this can damage your fingers if you hold it more than a moment. The temperature of dry ice is minus 80 degrees centigrade. This is 80 centigrade degrees colder than ordinary water ice. When you recall that the difference between ice and boiling water is 100 centigrade degrees, you are not surprised that dry ice has a fierce frosty bite.

Dry ice is carbon dioxide reduced to its solid, or frozen, state. It is called dry because it does not melt to a liquid when the temperature rises. At room temperature, it changes straight from an icy solid to its gaseous state. It is fine for chilling picnic lunches and cold drinks. But let's beware of the fascinating stuff, keep it safely wrapped and refuse to let it frost bite our bare fingers.