Steve Gasaway, age 9, of High Point, N.C., for his question:

WHAT MAKES WATER HARD?

Soft water merrily mixes with the soap to make masses of foamy lather. This sort of froth gets out the dirt in a hurry. Strange to say, all our water starts out as soft  raindrops, freshly fallen from the clouds. Then it runs toward us over and through the ground, dissolving all sorts of chemicals from the soil and rocks. If our water supply happens to run through limestone type rocks, it dissolves certain chemicals that make the water hard. This hard water refuses to play with the soap to get out the dirt. Instead, it forms that scummy stuff that leaves a rough ring of grime around the bathtub.