SIMPLY SCIENCE: Digging deep for the real truth about moles

This time of year people have trouble with moles. We are several weeks into the school year, and chemistry students everywhere are concerned about moles. However, I don’t think they are interested in saving the moles. I think they would like moles to become extinct.

They were taught in earlier grades that moles were cute little animals that lived under the ground and sometimes caused bumps in the lawn. Technically, moles are neutral, being neither good nor bad. But bumps in one’s lawn are as socially unacceptable as water spots on drinking glasses.

This is how we do it in education you know. We don’t exactly tell the truth. Because the world can seem complicated and, for the most part, adults are pretty poor tellers, we gloss over parts of the world with lies. In the second grade, we correct some of the lies. This usually results in more lies.

Somewhere along the way, we hope we get all the lies corrected and leave students with the truth. I can tell you from experience, though, that the point of truth in this process is longer than 10 years of higher education. I just do not intend to pursue it any further, because my wife said I can’t.

We put off difficult concepts until children are older. For example, we usually let them think of moles as little animals until they start asking grandpa why he has that funny brown bump on his face. Exactly when to introduce the concept of a mole as a pigmented skin blemish is best left to the parent’s judgment. The public education system should not be involved in this at all.

The truth is: A mole is the amount of a substance that contains as many particles as there are atoms in 12 grams of pure carbon-12.  This corresponds to 6.02 ×1023 elementary particles of that substance. What?

(Society has decided that sometime in high school is the appropriate time to spring this radical information on unsuspecting children.)

I think they meant to say that one mole is the number that indicates the mass (in grams) equal to the atomic weight of the molecule. For example, water has an atomic mass of 18; therefore one mole of water weighs 18 grams, and contains 6.02 x 10 molecules.

Lorenzo Romano Amedeo Carlo Avogadro was an Italian born in 1776. (I know that date from somewhere.) He was first a lawyer and then became a chemist. That right there probably explains a lot of the difficulties people have with moles.

Anyway, Avogadro hypothesized that the number of atoms in an amount of material, equal to the atomic weight of that material expressed in grams, would be 6.02 ×10 for all atoms. No, this is not to be confused with the calorie count for avocado dip, though they are similar.

Avogadro’s number is a very large number. An Avogadro’s number of “avocados” would cover the entire Earth to the depth of several hundred feet. I wonder how deep it would be if the avocados were made into dip?

Another way of expressing this law is to say that equal volumes of ideal gasses, at the same temperature and pressure, contain the same number of particles. Of course, problems arise in defining the words “equal,” “ideal,” “same,” “temperature,” “pressure” and “is.” When these things are considered, Avogadro’s law isn’t true at all. The law is just another approximation (which is a fancy word for lie). As soon as you think you understand this lie, I will tell you the truth.

At this point I hope you are a little less confused about moles. To put it simply, they are either vertebrates, skin blemishes or a number. Really pretty easy to tell apart. But if you are still confused, have hope. Oct. 23, from 6:02 a.m. until 6:02 p.m., is International Mole Day sponsored by the National Mole Day Foundation.

Save the moles!

Gary McCallister is professor of biology at Colorado Mesa University.


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