Science Lesson Size of Molecules

A science lesson featuring a number of examples of the size of molecules to help one understand the size on a molecular scale.


Most molecules are of such small dimensions (the number of molecules in 1 cubic centimeter of water is about 3.3 x 1022) that even scientists experience considerable difficulty in visualizing their relationship to the everyday physical world. For this reason, a few data will be devoted to this problem by considering molecules in line, on surfaces, as individual units, and in bulk.

A Chain of Iron Atoms. A chain composed of as many iron atoms as there were people in the U.S. in 1960 (180 million) would extend for a distance of approximately 2 centimeters (less than 1 in.).

A Monolayer of Molecules. If every square meter of the earth's dry surface were occupied by 6 men, their total would approximate the number of molecules in a monolayer of air one centimeter square (1,000,000,000 million).

A Teaspoonful of Molecules. One teaspoonful of water contains at least as many molecules as the Atlantic Ocean contains teaspoonfuls of water.

Columbus's Water Molecules. If Columbus had emptied a glass of water in the ocean, and assuming that this water were now thoroughly mixed and distributed through the seas of the world, then each glass of water taken from the nearest tap or other source of water would now contain up to 250 molecules of the original contents of Columbus's glass.

A Handful of Snow. If all the molecules in a handful of snow were magnified to the size of a pea, there would be snow enough to blanket the entire surface of the earth to a thickness covering the Eiffel Tower or Rockefeller Center in New York, i.e., 300 meters (330 yd.).

Hospitality with Molecules. Peter looked askance at John, who was just polishing off his umpteenth glass of whiskey:

"Steady on, old man . . . leave a drop for the stragglers!"

"Shteady on?" echoed John. "Why, there'sh heapsh of the shtuff . . . hic. Tell you what, shport, I'll dish out a thousand moleculesh per shecond to every living shoul for the nexsht thirty-odd yearsh . . . hic."

John upturned his empty glass and shook a single drop onto Peter's palm. "Take care of the distribution, shport!"

Counting Molecules. Counting by hand the individual molecules composing 1 cubic centimeter of water at the rate of one per second, the whole of recorded history would still represent the merest fraction of the time necessary to carry out the operation.

If the task had been finally completed today by an army of counters equal to the population of the city of Rochester, N.Y., the 300,000 participants would have had to have begun counting the water molecules three thousand million years ago, i.e. at about the time the earth is now thought to have been created.

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