National Mole Day 10/23/22

Science with Richard Bleil

Today, October 23, from 6:02 in the morning until 6:02 in the afternoon is National Mole Day.  No, not mole like the fuzzy little blind creatures digging up my lawn, but the chemistry mole.  Early in chemistry, Dalton suggested that atoms of two or more different elements bond together in specific whole number ratios to form compounds, but chemists needed a way to understand this and to convert from the concept of bonding in simple whole number ratios to measuring quantities in the lab. 

Let’s take, for example, carbon disulfide, or CS2 (where the 2 is supposed to be a subscript).  This ratio tells us that one carbon will react with two sulfurs to form the compound, but in the lab, there was no way to show the ratio of 1:2.  Instead, experimentally, it was discovered that 12 grams of carbon would always bond with 56 grams of sulfur forming 68 grams of the compound. 

Before Avogadro, there really was no way to make sense of these masses.  Dalton suggested the ratio of atoms was a simple ratio not based on mass but on atoms.  One carbon and two sulfur atoms to form the compound, but there is no way to measure the number of carbons and atoms.  It was Avogadro who figured out that different elements had different average masses.  To assign the masses to the elements, he chose a scale that was easy to measure in the lab.  So, the atomic mass (average mass) of carbon was 12, and that of sulfur was 28. 

See, sulfur is 7/3 times heavier than carbon, so 28 grams of sulfur has the same number of atoms as 12 grams of carbon.  Avogadro didn’t know what this number was, so he called it a mole.  A mole is simply a number, as any number would work.  To say one atom of carbon bonds with two atoms of sulfur is no different than suggesting that one dozen carbon atoms would bond with two dozen sulfur atoms.  The ratios of dozens are the same as the ratios of atoms.  So, one mole of carbon would bond with two moles of sulfur because the ratios of moles are the same as the ratios of atoms. 

Eventually it was deduced that one mole is 6.02×10^23, or 602,000,000,000,000,000,000,000 or six hundred billion trillion.  By comparison, today the national deficit in the US is only seven trillion, 7,000,000,000,000 or 7×10^12.  Multiply this by a billion and you’ll have about a mole.  This number is not arbitrary, but rather, is large enough that masses of elements can be reasonably measured on laboratory balances.  So, since a mole is 6.02×10^23, national mole day is 6:02 AM to 6:02 PM on October (10) 23. 

The American Chemical Society uses this day to raise awareness of chemistry.  The American Chemical Society is the professional society to which most (if not all) chemists belong.  It handles the vast majority of publications in the field of chemistry in the nation, puts on seminars and deals with national issues in chemistry.  Whether we are aware of it or not, chemistry is all around us, and with the exception of a few topics of physics (such as radiation and energy), everything is chemistry, including other sciences.  Chemistry is the study of matter, so the question is, “what’s a ‘matter’?”  Well, nothing, what’s a matter with you?

Matter is anything that has mass and occupies a volume.  So, heat is not matter, because even though we can feel it, heat does not occupy a volume.  But most anything that we can see, touch, feel, smell is matter.  The device on which you are reading this is matter.  The clothes you are wearing is matter.  When you eat, the food is matter.  Heck, you are matter as well.

Chemistry is behind everything (with the aforementioned exceptions), including abstract concepts.  Chemistry is responsible for love, for example.  I used to like challenging my students with this concept, but love is a feeling, and feelings are assigned in our brains.  Oxycotin, for example is the hormone released when we’re in love, and this hormone (as all hormones) is a chemical.  So, yes, even a concept as abstract as love is due to chemical processes. 

It’s important to note that chemistry professors, like me, tend to lie to our students.  We tend to give a picture of what we “know” in class as a pretty little complete picture, but there are gaps in that picture if you really stop to think about it.  And, like any science, nothing can really be proven to be true in chemistry, including atomic theory.  Tomorrow, some particularly bright young person might come along and prove atomic theory is wrong.  Scientific “truths” are not truths at all, but rather models that to the best of our ability explains the body of observational knowledge we have accumulated over the years, but it’s rarely presented as such.  We can prove some ideas wrong, but nothing can be proven true, although, as additional evidence is accumulated, the odds that some of these theories (like atomic theory) is wrong becomes increasingly unlikely.  But as you spend the day today, just give a thought about chemistry, and the reactions and processes that are occurring every day.

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