John O'Hara Jr., age 11, of Hutchinson, Kan., for his question:

JUST WHAT IS A SOLVENT?

A solvent is a liquid that dissolves another substance and forms a solution. Water is the most common solvent. It dissolves a great many substances, including sugar, salt, air and alcohol.

Turpentine, another common solvent, is used to wash oil base paints out of paintbrushes. Turpentine will also dissolve paint stains out of clothing.

In a solution of two or more liquids, the most abundant liquid is called the solvent. As an example, vinegar consists mainly of water and acetic acid. This solution contains more water than acetic acid, so water is called the solvent. The acetic acid is called the solute.

A solvent that has dissolved as much solute as possible is said to be saturated. As an example of this, when water has dissolved so much salt that more salt cannot be dissolved, the water is saturated with salt.

The amount of solute that a solvent can dissolve depends on the chemical properties of both substances and such conditions as temperature and pressure.