Barbara Johnson, age 13 of Omaha, Nebraska, "‑
How many atoms are there in a molecule?
How many people make a family? Families, of courses come in all sizes, There may be only two members. There may be ten persons in a family or any number you name up to twenty and even more. The same is true of the atoms that make up a molecule. There may be but two atoms in a molecule. There may be any number you name up to a hundred, And some molecules are families of many hundreds of atoms.
Even the biggest molecules are too small to be seen. They cannot be seen even under a powerful microscope. How can we believe in them? The experts have tracked them down by studying them in large groups, They tell us that everything in the world is made of tiny atoms and molecules; You can try a simple experiment to discover some of this for yourself.
Stir a little salt in a little water. The salt dissolves and disappears. Maybe it is gone for good. Taste the water and see. The salt is still there. The gritty solid crystals have broken into tiny tiny particles. Each particle is small enough to dissolve and hide in the water. But it is still there and still a fragment of salt. You can prove this too.
Leave the salty water in a shallow dish. The water will gradually evaporate and go off into the air. But not the salt. When all the water is gone$ there is your salt in the bottom of the dish. The tiny fragments that were in the water have gathered together to form solid crystals of salt again.
Is each of these crystals a molecule of salt? Each little crystal is made of billions and billions of molecules of salt. These little molecules split off on their own when they dissolved in the water. On its own a single molecule is too small to be seen. But the salt in the water was made of molecules and so are the solid salt crystals, Now we can believe that everything else in the world is also made of tiny molecules.
If a molecule is so small., it must be almost impossible to imagine the smallness of an atom. This may give you some idea. There are about two billion people in the world. Suppose we all shrank to the size of atoms.