Eddie Wolfe' age 12, of Rensford, West Virginias for his question:
What is a molecule?
The concept or idea of a molecule is not an easy one to grasp. But it is a vital step in the study of chemistry. One reason for the confusion is a rather :sloppy use of the word molecule, even by experts. This, says Andy, is very unfair to a young person trying to get his first grasp of a scientific subject.
What we need here is a word to describe the smallest particle of any substance. Many precise scientists have different names for the smallest particles of water,, salt and cellulose. They call the smallest particle of water a covalent bond, the smallest particle of salt an ionic crystal and the smallest particle of cellulose a molecule, It is true that there are basic differences in these particles and certain experts are very strict about giving them different names.
Other experts use the word molecule to describe the smallest particle of any substance or compound. This is, perhaps, an oversimplified method. But, since even experts are not always clear, we must decide for ourselves how we will use the word molecule. Andy suggests that we use the simplified term while we are exploring step one. WE will begin by calling the smallest part of any substance a molecule. If you go on with the study of chemistry you will learn that these particles are of vastly different types. Then you may use and become familiar with their more specialized names.
We often are told that everything in the universe is made of atoms. Atoms are the smallest particles of the elements and there are only about 100 different elements in the whole universe, Different atoms tend to combine with each other in tight little bundles. Two atoms of hydrogen gas will combine with one atom of oxygen. The result is a molecule of water, a particle which is quite different from the separate atoms of hydrogen and oxygen.
When an atom of nitrogen combines with three atoms of hydrogen a molecule of ammonia is formed. The; clement sodium is a metal,, the element chloride is a gas, When one atom of sodium combines with one atom of chloride they form a molecule of ordinary salt. These are examples of smallish molecules. Each molecule of cellulose, the main ingredient of wood, contains six atoms of carbons ten of hydrogen and five of oxygen. Certain larger molecules are composed of hundreds of atoms.
Every molecule of water is exactly like every other molecule of water. Every molecule of salt is exactly alike. The idea of molecular particles is this: We know that salt, say$ is composed of the elements sodium and chloride But the ingredients are not mixed together like a pail full of sand and gravel which can be separated through a sieve. The ingredients of salt are in tightly bound, identical molecules, each containing one atom of sodium and one of chloride.
A molecule of salt is the smallest possible particle of salt. A molecule of water is the smallest possible particle of water. How small are these molecules? A little white crystal of salt is a delicate latticework of millions of identical molecules. A drop of water contains as many identical molecules as there are people in the world: