Jimmy Wehking, age 11, of Houston, Texas for his question:

What is heavy water?

Water, like everything else in the world, is made from atoms of the basic chemical elements. The smallest particle of water is a unit called a covalent bond, which is a special kind of molecule. This unit is a bundle of three atoms linked together by the sharing of their electrons. It contains one atom of oxygen and two atoms of hydrogen and these individual particles of water tend to link themselves together in pairs.

Maybe you have heard water called H 2 0. This is chemistry shorthand which tells us that a basic particle of water contains two atoms of hydrogen and one atom of oxygen. But in all the water in the world, there is about one particle in every 5,000 particles which is slightly different from its neighbors. It as a particle of heavy water.

This particle of heavy water is different because of a special kind of hydrogen atom called an isotope. The ordinary hydrogen atom contains one proton particle in its nucleus and one orbiting electron. An atom of the isotope heavy hydrogen, which is called deuterium, contains a neutron particle in its nucleus in addition to its one proton.

The ite deuterium is about twice as heavy as ordinary hydrogen. This atom adds extra weight when it occurs in a particle of water. In nature, such particles of heavy water are rare. The job of preparing a quantity of heavy water in which the istope deuterium is used in place of ordinary hydrogen must be done in a laboratory.

Heavy water looks and feels like ordinary water, but it has different chemical properties. Ordinary water boils at 100 centigrade degrees, heavy water boils at 101.42 degrees. Ordinary water freezes at 0 centigrade degrees, heavy water freezes at 3.82 degrees..

Heavy water, then, has a slightly higher boiling point and a still higher freezing point than ordinary water.

Seeds refuse to germinate in heavy water, tadpoles and certain other animals cannot live in it. But heavy water is a very useful liquid in the field of atomic energy. It can be used to discipline the furious energy of an atomic pile. It can be used to take the heat from an atomic pile and put it to use. Some of the reactors which generate atomic energy use heavy water as a moderating agent to control the atomic energy which is released by chain reaction. Score reactors use heavy water as a cooling agent to reduce the seething temperature of the atomic pile and syphon off this heat, using it to make electrical power.

This man made heavy water, so useful in the field of atomic energy, is called deuterium oxide. So far, our chemists have not found a cheap way to produce it and deuterium oxide is a very expensive fluid. If we find an easy way to separate that one particle of heavy water from some 5,000 particles of ordinary water, the cost of producing atomic power will be much less.