Helen Pasos, age 9, of Santa Maria, California, for her question:

Does chalk have other uses besides blackboard writing?

Chalk is just fine for writing on the blackboard. But it can do a lot of other useful things too. It is easy to grind the soft, crumbly stuff to powder. If you mix it with water, you pet a clean white paint. This was used in olden days to paint fences, walls and ceilings. However, it soon flaked off or got washed away by the rain. They still add powdered chalk to certain paints. But they also add other ingredients to make them stick tighter and last longer.

They also add chalk to tooth powders and fine cleansing powders. A rubber ball is made from rubber and extra ingredients. One of the extras may be chalk. Sometimes gardeners strew chalk around to help soil that is too acid. And they also put chalk in cement. The cement is mixed with moisture and sandy ingredients to make concrete. With all these useful duties, it is a wonder that there is any chalk left to write on the blackboard