Archive for November 2012

Amping up the Enlightenment

It is a truth universally acknowledged….that chemists avoid physics and physicists avoid chemistry. Of course, I’m not saying that scientists are devoted only to their field of expertise and prejudiced against all the others. We’d know a whole lot less about the world if that were the case. I think it’s safe to say that people of all backgrounds like to stick to what they know, whether it’s philosophy or physics.

From: xkcd.com

Unfortunately for scientists, there is an inconvenient amount of overlap between areas of research. This overlap makes communication between biologists, chemists, physicists, etc. absolutely essential. So, in that spirit, let’s venture into the dangerous no-man’s land that is physical chemistry. Physical chemistry (or “p-chem”, if you’re a super hip college student), is, “the branch of chemistry concerned with the interrelation of the chemical and physical properties of matter and the application to chemical systems of the principles of physics (in thermodynamics, kinetics, electricity, spectroscopy, etc.).” Or, in normal-people words, it’s a study of how and why atoms work, and how that knowledge can be used to make things like computers and efficient engines.

I’ve suspected for a while that the physics I’ve been learning is actually chemistry (though the physicists would say that the chemistry I’ve been learning is actually physics). My suspicions were confirmed when I visited the Franklin Institute in Philadelphia, and they had a whole room devoted to explaining electricity. This was really awesome, since we’ve been learning all about electricity in physics class. But I thought that electricity was exclusively physics…..

Yet, lo and behold, there were a number of diagrams…of atoms. As it turns out, electric charges are the result of atomic structure. Atoms are made of positively charged protons, negatively charged electrons, and neutral neutrons. Protons sit in the middle of an atom with the neutrons (composing the nucleus), and the electrons zoom around this dense center, forming an “electron cloud”. Being an electron’s like riding the teacups at Disney World forever, except without tracks and in fast-forward. Atoms are held together by the attraction between the negatively charged electrons, and the positively charged nucleus (just like the opposite poles of magnets stick together). The charge on these particles is inherent, meaning that electrons and protons have charge by virtue of being electrons and protons, just like you’re however old (young?) you are because you’ve lived for that many years.

This is a basic diagram of an atom, with protons, neutrons and electrons labeled.

If an atom loses an electron, it becomes positively charged. If an atom gains an electron, it becomes negatively charged. Atoms don’t lose protons. I’ve always wanted atoms to become more positive because they gain protons, but it just doesn’t work that way. This idea of atomic charges becoming more or less negative applies to whole objects, too. This time of year, everyone starts getting static shocks, because there’s less moisture in the air. Shocks from your sweaters, your car, door knobs, and so forth. The Franklin Institute actually had a sign at the entrance to the electricity exhibit warning people that some of the interactive displays could generate painful shocks. People touched them anyway, of course, and then laughed about it while getting their friends/children/spouses to “learn” about static electricity.

Some atoms want to get rid of an electron, and some want to have more electrons, all in the pursuit of stability. Everything from people to buildings to atoms is happiest when stable. As a result, sometimes atoms let go of their electrons. Sometimes atoms want to get rid of their extra electrons so badly, the electrons actually jump from one material to another. It’s like carrying groceries into your house, and you’re struggling with three heavy bags, but the person who was riding shotgun is bringing the eggs inside. You want to give them one of your bags, and they (assuming they have a conscience) want to take one from you because they feel guilty about not helping. Without ever actually touching each other, you transfer a bag as quickly as possible, hoping no one spills the milk. This is basically what happens when a positively charged material comes near a negatively charged material. The negatively charged material has an excess of electrons, and really, really wants to donate some of those electrons as soon as possible (if only people were so eager to make donations!). This jumping between positively and negatively charged materials is how you can get a shock from a door handle before you actually touch it.

Since we’re on the subject of static electricity (which can be a bit of a bore since there’s really nothing shocking to learn about it), I think it’s worth shifting topics slightly to talk about how electricity is generated in those wind-up flashlights. I learned about this by accident one afternoon while studying in the physics office in the basement of the science building (i.e. my secondary address). My professor was building an experiment on the table I was working at (because that’s what professors do when they’re not teaching class- devise ways to challenge (torture?) student in lab). The experiment involved those flimsy plastic race track pieces and, naturally, a little Hot Wheels car with a magnet attached. It also involved a bunch of copper wires through which the track went, all attached to a multi-meter, which reads how much voltage or current is generated in a current. As it turns out, you can actually create an electric current by passing a magnet quickly through a bunch of wires, which totally blew my mind. So, when you’re cranking the, uh, crank on a wind-up flashlight, you’re pushing a magnet through a coil of wire over and over to generate electricity to light up the bulb. There’s no Hot Wheels car inside the flashlight, although that would be pretty cool….

So, maybe you’re wondering how the heck a magnet running through some wire can create electricity. I certainly was. This method of generating electricity is called induction, and was discovered by Michael Faraday in 1831. We named the Farad after him. Magnets create magnetic fields, which is like the area that’s affected by the magnet, like how the iron filings are affected by the magnet in this picture:

The movement of the magnet and its field creates an electric field in the coil because the magnetic field pushes and pulls electrons (and there are a lot of them in a wire) until a current starts flowing.

Faraday's Electromagnetic Lab

Click to Run

The electromagnetic force causes this push and pull, and we wouldn’t have generators in our houses or power plants  (or more importantly, wind-up flash lights) without it.

I’ll stop here, before I get ahead of myself by attempting to cover an entire semester of physics with one blog post.

Did I say physics? I meant chemistry.

Leave comments if you have questions- I know this post got a little technical.

-Ashley

Oh, and a little more Bill Nye before you go:

Sources: Physics for Scientists and Engineers: A Strategic Approach by Randall D. Knight (Volume 4, 3rd Edition)

Philly!

I’m really getting around this Thanksgiving break. Lynchburg, Philadelphia, Nashville, Manassas. Phew! I don’t think I’ve ever covered so much land in such a short span of time. The highlight, and most relevant to my blog, was my trip to Philadelphia. The purpose? Science museums! Philadelphia has many fantastic museums, many of which are science-oriented and everyone-friendly. I visited the Chemical Heritage Museum, the Franklin Institute, the Academy of Natural Sciences and the Mütter Museum. My goal was to learn how to better educate my readers about the amazingness that is science without making it seem super lame by adding too many words like Buckminsterfullerene. As a chemistry student, I found the interactive exhibits fun and engaging, but so did the parents….and their five-year-olds.

The first thing I did last Friday when I arrived in the city was head to the Chemical Heritage Museum, where I spent several hours reading everything. I’d never been somewhere so enthused about chemistry. However, my favorite out of the four museums I visited was the Franklin Institute. It was so incredibly interactive. There were levers, buttons, switches, knobs….all of which subtly sought to teach the viewer something about physics (or other sciences that Benjamin Franklin explored (i.e. all of them)). There were also small children running around shouting, “Yaaaay! Science!” which warmed my heart, which was cold from walking the windy Philadelphia streets.

Natural Science museums are always educational. The Academy of Natural Sciences had dinosaur bones, so, yeah. Worth the trip. They also had a preserved tuna fish that Ernest Hemingway caught (an intersection of the sciences and the humanities).

 

The Mütter Museum is one I’d never heard of before actually going to Philadelphia and leafing through a myriad of tourist pamphlets. It exhibits an fascinating medical collection of skeletons, preserved body parts, and wax models of various diseases. In addition to exploring the museum exhibits, I actually had the opportunity to speak with staff members at the Chemical Heritage Museum and the Academy of Natural Sciences, who kindly answered all my questions about relating technical information to the public. Museums are a great way to learn about….well, anything. I definitely recommend a trip to Philadelphia to check out everything the city has to offer, especially these great institutions.

 

 

-Ashley

 

Lightbulb Moment

Nothing has ever made me look at the world around me and think, “and all this actually works?” like organic chemistry class has. Nature is so incredibly complex, it’s difficult to contemplate how everything, right down to the atomic level, functions harmoniously to make life work. What I find most intriguing are the little tidbits of explanation that make me go, “oooooh, that’s why”. Followed, of course, by a tiny lightbulb illuminating above my head. One of my favorite tidbits has to do with our sense of smell.

Vanilla Flower

Like our ability to see, it’s easy to take our ability to smell for granted. Before last spring, I’d never thought about why or how we’re able to smell the roses. As it turns out, up inside our noses (lovely image), there are like 50 million teensy tiny receptor cells. These are basically cells with locks on them, and only a certain kind of key (a specific molecule) will allow them to tell your brain that your smelling something. Not only will that key unlock your sense of smell, but it also allows for identification of the smell and instant recollection of memories associated with it (that way your brain can tell you to get inside when it’s about to rain).

The first step in the creation of aroma is the dispersion of potentially odorous molecules into the air. This happens when things evaporate or are otherwise made into tiny, airborne particles (like how asphyxiating cedar dust is thrown all over as the chainsaw devours a tree trunk). If you get close enough, or there’s enough of a molecule in the air (many parts per million, or ppm), some of those molecules will get into your nose. Once inside your nose, they molecules will drift up to your olfactory epithelium, where all those cells with receptors live. If you have a receptor for the molecule that’s in your nose, you’ll be able to smell it. Some things are “odorless,” like methane from a gas stove (which is why they have to add a smelly compound to it for safety). There simply isn’t a receptor in the human nose that matches the shape of the methane molecule, so we can’t smell it. It’s kind of like that old saying about trees falling down in the forest with no one around to hear. Just because you can’t smell it, doesn’t mean it’s not floating around in the air (and this is where I tell you to buy a carbon monoxide detector for the second time).

What’s really amazing about our sense of smell is how precise the receptors are. There are a lot of molecules that look very similar, but are actually detected as unique by our nose, eyes, hands, etc. It probably makes sense that huge molecule, with like 60 carbon atoms on it, might smell different than a little molecule, with 5 carbon atoms. But, our noses are even better than that. We can actually distinguish between two molecules with the exact same number and types of atoms that are “chiral”. A “chiral” molecule means that there are two version of the same molecule, but one of them is like your left hand and one of them is like your right hand. They look a whole lot alike, and can even do many of the same things, but when you put one on top of the other, they just don’t quite match up (superimpose).

Strikingly Similar

As you can see, these two molecules look a whole lot alike. But your nose can tell your brain which is the tangy caraway (left) and which one is refreshing spearmint (right). Super cool. Both versions are called Carvone. These types of molecules are called enantiomers, and they play a lot of really important biological roles. For example, natural adrenaline that your brain makes fits into an enzyme that gives you that jolt of energy. Unnatural adrenaline (man-made) is the enantiomer of the same adrenaline molecule found in nature, and it lacks that jolt.

There’s a ton of chemistry involved in sensory perception, from the shapes and sizes of molecules to the actual atoms that make up the compound. Some molecules that lie in flat lines smell bad because they sort of sharply poke the receptor cells, and Sulfur is responsible for the classic rotten egg smell.

 

My Eye

I hope this is at least half as mind-blowing to you as it is to me. I mean, seriously. My eyes can’t see the difference between a caraway molecule and a spearmint molecule, but somehow my nose knows.

 

-Ashley

 

 

Sources: Organic Chemistry, Seventh Edition by L.G. Wade, Jr. (Prentice Hall), and Dixie State University of Utah powerpoint: http://cactus.dixie.edu/smblack/chem1010/lecture_notes/2D_chemistry_of_smell.pdf