Monday, April 22, 2013

A Big, Deep Yoga Breath


The West, Texas fertilizer plant explosion of last Wednesday killed many of the town’s first-responders and leveled buildings and homes and left behind a giant crater. I heard the question asked, how can fertilizer be so dangerous? (I even heard someone mention manure when referring to fertilizer, so there’s a chemistry lesson here.)

Close your eyes. (Oh wait, you can’t close your eyes and read at the same time!)  Ok, read the next few sentences, THEN close your eyes.

Take a big huge breath with your eyes closed.  As my yoga instructor would say “a big, juicy, fill-the-bottom-of-your-lungs yoga breath,” and then hold it for just a moment and let it all out.  (Ok, now close your eyes and do it.)

 

 

Waiting for you to finish…

 

 

You just breathed in air that contained mostly nitrogen molecules, N2.  Your lungs took in 1023 (or so) molecules of nitrogen and you did not use single one of them. They just took up space in your lungs.  Dry air is composed of 79% nitrogen and 20% oxygen and then a smattering of other gases like carbon dioxide and argon.  The nitrogen molecule is rock-solid stable.  There is a triple bond between the nitrogen atoms and not much can cause that bond to break.  But N is essential to our bodies:  muscles and enzymes are composed of amino acids which have nitrogen atoms in them.  How do they get there? 

We eat them those N atoms. We eat plants, or eat animals that ate plants. If nitrogen is so hard to break apart, how can plants get the nitrogen?  There are two principal methods for nature to get the N into the plants. One, lightning passes through the air and can break up nitrogen into compounds like nitrates containing both nitrogen and oxygen. Marvel at that, it takes a lighting strike! Or, bacteria on the roots of plants such as beans and peas can “fix” the nitrogen in the air. That’s it. So, the miracle of nitrogen-based fertilizer is that it helps nature along a bit by putting the N into plants. The stuff is explosive because it can release the N2 back to the air and the energy flies from the fertilizer into the atmosphere as that super stable triple bond forms. 

So next time you take a yoga breath, first, say a prayer for that grieving town in Texas and next, remember you may not be able to touch those nitrogen molecules, but you need them all the same.

Sunday, April 21, 2013

Pressure Cookers: Put a lid on it

The Boston Marathon bombers used pressure cookers. Before Patriot’s Day 2013 I had no idea that many of the IEDs used in Iraq and Afghanistan were fashioned from these wonderful cooking devices.
Every year when we discuss boiling points and vapor pressure in my chemistry class, I talk about pressure cookers. My mom had a pressure cooker when I was growing up, and many of my Indian students’ families routinely use pressure cookers.
It was common for my mom’s generation to can or “put up” fruits and vegetables. They had been children of the depression and had been teenagers during the Victory Garden years of World War II; growing and preserving vegetables and fruits were expected practices in the summer and fall. The problem was that non-acidic vegetables like green beans and corn could not be canned safely without risk of botulism contamination. Botulism spores can survive boiling water; they need to be heated to 250 degrees F or 120 degrees C to render them harmless. (You could pickle the veggies: the acid in thevinegar kills the bacteria.) 
The heavy-walled pot has a lid that can be sealed tightly with a rubber gasket keeping the steam from escaping. Excess steam can be released through a release valve. Pressure builds up inside to the pot. Water boils when its vapor pressure (a measure of the amount of forces holding water together) is equal to the surrounding pressure. Since the pressure is higher in the pot, the water boils at a higher temperature and food cooks faster and botulism bugs are killed. Dentists and hospitals use them to sterilize instruments between patients. These are truly marvelous inventions.
Now, when I talk about boiling point and vapor pressure, I will have to add comments about pressure cookers being used as bombs, just as I discuss the Oklahoma City bombing when I discuss nitrogen-based fertilizer. Sometimes connecting chemistry to current events just stinks.

Thursday, April 18, 2013

Chemical Vision




If I were to start a blog about writing, I would make sure that every single post that I wrote was free of spelling errors, punctuation problems, and awkward or incorrect grammar.  If I am writing about writing—I better be able to demonstrate to the world that I can write.  Split infinitives and dangling participles are abhorrent to those that read good writing.


If most people look at the two molecules at the top of this blog post, they do not see anything other than two rather similar structures rendered to be pretty and shiny, blue and yellow (and red, in the case of the second molecule.)  Someone who knows chemistry, would look at the pretty shiny molecule on the left and say, “Hmm. Something is funky here, that does not look quite right.” Or maybe a bit more forcefully, “Whoever put together that drawing does not understand chemistry.”  


The molecule on the left is gibberish.  It is spelled wrong.  It simply does not exist.  (Maybe it could exist if the gold atoms were assumed to be oxygen and the hydrogen atoms that should be attached to the gold oxygen atoms were implied, but that is stretching it.)


The molecule on the right makes perfect sense:  four bonds to carbon, three bonds to nitrogen, two bonds to oxygen, and one bond to hydrogen and the angles between the bonds have the correct measures.  In fact, the coolest thing is that someone who knows chemistry automatically sees those atoms (carbon, nitrogen, oxygen, and hydrogen) in those positions, without being told what they are. In fact, there are chemists out there that would look at that molecule and think of coffee.  (The molecule is caffeine.)


I have been teaching chemistry for twenty years.  It is a truly marvelous thing when my students start to “see” molecules and structures as a chemist would.  In my organic chemistry class, we call this magical moment the epiphany, the “AHA!” moment when all the reactions, mechanisms, electrons, and arrows seem to dance in an organized way.  


Organic chemistry then becomes a set of puzzles instead of a bunch of note cards, because my students have learned a new way to see.