Adele Penland, age 14 of Asheville, N.C., for her question:

WHAT IS RUBBING ALCOHOL?

The substances known as alcohols are chemicals that have the same single characteristic in their makeup: a hydrogen atom attached to an oxygen atom, which in turn is attached to a carbon atom. This property gives them the unusual power to dissolve many organic compounds, and alcohol in industry is used for this very purpose.

Ethanol, or ethyl alcohol, is made by the fermentation of fruit juices. Industrial ethyl alcohol is made from potatoes or grain, chiefly corn, the starch in corn being treated with malt to convert it into fermentable sugar.

Rubbing alcohol is usually ethanol, and it is useful for sterilizing surgical instruments because it kills many bacteria.