Tommy Constable, age 11, of Phoenix, Ariz., for his question;
What are elements and compounds?
The chemical elements have recently starred in a TV series. Also starring are a host of the great scientists who contributed to our understanding of the basic elements. Ernest 0. Lawrence, Nobel prize winner for invention of the cyclotron, shows how his machine works to change the basic elements. Glenn T. Seaborg, Nobel Prize winner as co‑discover of the element plutonium, narrates and demonstrates the fascinating story of the ingredients from which the world is made.
Everything in the whole universe is made from a hundred or so basic elements. Each element is made from atoms of a certain kind. The element iron is iron atoms. Pure gold is made entirely from atoms of gold. An atom of iron is the smallest particle of iron and an atom of gold is the smallest particle of gold. Each is different from the other and both are different from every other kind of atom.
Atoms are restless bits of matter. They tend to team up in assorted bundles. In nature, pure elements are rare. Most of the everyday substances are combinations of elements. We call these substances of mixed elements compounds. Salt, wood, glass and sugar are three examples of the thousands of different compounds in the world, is made from about 92 chemical elements. Some are rare and some are plentiful. Some are good mixers and some rarely team up to form compounds with other elements. oxygen is a good mixer and very plentiful. It combines with other elements to form almost half the rocks of the earth's crust. Helium is a rare gas and it is reluctant to form compounds with other elements. This element is named from Helios, the sun, because it was found on earth only after it had been discovered in the sun each grain of sand and each chip of gravel keeps its own identity and can be separated with a sieve. then assorted atoms combine in molecules, theoriginal elements lose their identity and form an entirely different substance.
The gaseous elements hydrogen and oxygen combine to form liquid water. Carbon, hydrogen and oxygen combine to form sugar. Two or more compounds may combine to form a more complex compound. The molecules of some compounds are composed of hundreds of atoms. In this way, thousands of different compounds are built from a few basic elements.
The making of molecules to form a compound is called a chemical process. The breaking up of the molecules in a compound is also a chemical process. A tree uses the energy of sunlight to bind gases from the air and water and chemicals from the soil to make cellulose. This is a chemical process which uses up energy, A fire breaks up the molecules of cellulose into smaller particles again. This is a chemical process which releases energy. The basic elements themselves do not change. But they are constantly building and rebuilding into a variety of compounds to keep our changing world fresh and interesting.