Deborah Shapiro, age 9, of Costa Mesa, Calif., for her question:

WHY DOES ICE FLOAT?

Ice is nothing more than frozen water. But something else happens when it freezes: the ice increases in volume over the water by one eleventh. This means that when 11 cubic centimeters of water is frozen, 12 cubic centimeters of ice will be formed. Thus, ice is just a bit lighter than water, and for this reason ice will float.

Expansion of ice can also cause some water pipes to split open during winter. And if water freezes in a car’s radiator, damage could very well result.

Pure water and even moisture in the air will turn to ice at 32 degrees F. At this particular temperature, the motion of the water molecules becomes so slow that the water crystallizes and freezes into ice. Sea water, because of the impurities, freezes at 28.5 degrees F.