Larry Brown, age 14, of Tulsa, Okla., for his question:

Are wood molecules bigger than plastic molecules?

Wood is composed of several different molecules, about half of them cellulose. Cotton and linen are composed almost entirely of cellulose tend it is the cellulose molecule which is used in the making of plastics.

The chemical formula of a substance is not quite the same as a single molecule. The formula gives the ingredients the chemical in a substance in exact proportions. The chemical, formula for cellulose tells us that it is composed of six parts carbon, ten parts hydrogen and five parts oxygen.

Basically, cellulose, is composed of countless little bundles, ouch containing six carbon atoms, ten hydrogen atoms and five oxygen atoms. Each little bundle is arranged in a special design which gives it an attraction for other such bundles and a tendency to form a pattern with them. Numbers of these basic bundles join end to end to form a long chain. This chain is the molecule of cellulose. It does not have to be any special length so we cannot say definitely how big a molecule of cellulose must be.

The chain molecule of cellulose accounts for its fibrous nature. A number of these chains lay side by side. When this happens, ties occur between them. Long thin chains become ladders and fiber of cellulose is composed of a great number of these chain molecules ‑all laddered together to form a sturdy thread.

A plastic material is one that can be shaped and molded. Clay is a plastic. A synthetic plastic is a moldable material made by the chemist from raw materials. And our wonderful chemists are busy developing more and hotter plastics for our everyday use. A whole group of these synthetics has cellulose as a basic ingredient.

You might suppose that the chemists either weld the basic molecules into larger molecules or break them into smaller molecules. This is not necessarily so. The trick is to rearrange the basic elements in the raw materials and to cause them to behave in a different manner.

One trick with cellulose is to dip it into a weak solution of sulphuric and nitric acids. This causes certain groups within the cellulose to become nitrates. The fibrous molecules of cellulose is still intact. But it will dissolve in a mixture of alcohol and ether as well as many other solutions. We now have a basic ingredient for making plastics called pyroxylin or cellulose trinitrate.

Old fashioned celluloid was made from a basis of pyroxylin with camphor added to give body. The durable automobile paints are made from a pyroxylin base, and so are countless other paints end coverings. Motion picture film and most other film is composed of a pyroxylin base. And the pyroxylin molecule is the cellulose molecule rearranged so that it will behave like a plastic.