Jim Hyde, age 11, of Omaha, Nebraska, for his question:

What are polymers?

Poly is a combining word form that means "many" and the term polymers refer to certain molecules. It is carried over in polyethylene and the names 'of other plastic materials. A polymer is a big molecule made of small molecules called monomers. Its monomers are all alike, usually bundles of just a few atoms. Our clever chemists use heat, pressure and other devices to bind numbers of monomers together in large polymers The units may be linked together in rings, chains or some other structure. The nature of the finished synthetic substance depends on these large and small molecules.

The monomer in polyethylene is the gaseous molecule ethylene. When heated under pressure and exposed to oxygen, basic monomers bond in groups and form large polymers. The process is called polymerization. In this case, the large polymers form molecules of polyethylene.