general chemistry

Chemical Edutainment and Undergrad Labs

So it’s me, the writer of solidasarock, and well I’ve joined the chemistry forums blog team. Studying for qualifiers have been awful, so writing has been almost nonexistent, but with finishing off TAing and watching the first years teach lab and hearing their complains that were oh so similar to mine last year, I thought I’d tackle something that’s really prevalent in some chemistry departments, particularly, my department. And that would of course me chemical edutainment.

<insert 2 cents>

I had the privilege of teaching freshmen, juniors, seniors and graduate students in my TA load, and seeing how things were run here versus my undergrad alma mater is disappointing. Back in my alma mater, experiments were ‘boring’. We didnt go into the latest nanotechnology, but we did go over very valuable experimental techniques. Twenty-thirty titrations in the first semester lab alone was enough to drive one insane, and the qualitative analysis freshman lab of having to figure out what ions were in a mixture was difficult for us fishies. Then of course, there was our ‘reward’ lab where we synthesized YBCO and then did a iodometric titration to determine the oxygen content, and then lots of other random labs that, while ‘boring’ to the students, showed important concepts that helped us conceptualize concepts.

Let’s compare that to my new department. Freshmen here do not do multiple titrations till they die. They dont even determine the concentration of their titrant in a standardization. Here, they do one titration, and do it using a pH meter. We didnt use a pH meter in undergrad until junior year for our titrations since we had to get a feel for the end point before hand. From there, they move onto ‘ubersexy’ labs, such as the synthesis of CdSe nanoparticles, Au nanoparticles. Did they at least characterize these NPs? They did one UV-vis, didnt really get told what was the significance and then were told to move on. Then later they had experiments that had very little chemistry in it at all.

I remember asking why these labs were taught, and I was repeatedly told about the ‘educational value’ of them. They were short writeups with barely any real analysis for the students. I chagrined and did my duty as a TA and taught them the best I could, inserting concepts, that while tangentially related, would actually be covered on their exams. Needless to say, my students complained at the extra work I had ‘assigned’. So writing down a few questions and having them answer it as part of their lab report was making me into a tyrannical despot. My evaluations were crappy, and I had learned my lesson.

I then spoke with one of the lab coordinators who told me about the consumerism of undergrad. We, as the TAs, are the product, and of course, the customer is always right. Of course! They pay $$$$$ money to attend this fine institution, but if they arent getting actual quality and instead get frou frou labs that teach them little but keep them entertained where is the value?

Now this sounds like a rant. Where is your proof? Like I said, I also got to teach juniors and seniors later on in the year, and I, to my dismay would find my proof there. Here are a bunch of chemistry juniors and seniors. I was explaining the quantitative analysis lab, and asked if they had done serial dilutions before. Nope. No one had done it. Unless they were a lackey in a biochem lab and had to do serial dilutions all day for their grad/postdoc mentors. Come on, at the junior/senior level, serial dilutions should be a snap. I explained the concept, showed them how to do it, and in the end, I was still asked by juniors and seniors to whether they could get micropippeters to dilute 1000x in a 100 ml volumetric flask.

I was dumbfounded. I was aghast. I wanted to rant and rave, but I kept it in. I taught them what they needed to know and went over the concept again. I had asked if they had covered it in organic lab (since I didnt get to teach that), and they said no. I knew the freshman curriculum, and I know it wasnt covered there. There were these chemistry majors, almost ready to graduate, not knowing very basic experimental skills.

So I was on fire and wanted to teach hardcore again. I went into other concepts that tangentially related, were still useful, and that they could use the information. A lot of them were happy at the knowledge, some werent. Then fast forward to another lab. These were the same juniors and seniors. I had assigned all the questions in the lab, but some were deemed too difficult. They saw no point in those questions. Needless to say, they went to my lab coordinator and complained to their hearts content.

I had a serious talking to again. Once again, they were right, as the questions were too hard. Of course, I didnt say at this point that the lab coordinator had written the lab completely and we both deemed prior that the questions were of the right difficulty and should be good for juniors and seniors. Since I was no longer entertaining them, since I actually went from ‘nice guy TA’ to ‘no, you need to answer these questions’ I was evil. I was a bad TA.

I was distraught. I really felt like I didnt want to be a professor anymore if things were going to be like this. Then I got to teach grad students, who all went to undergrad elsewhere. Thank GOD for grad students. And now I want to be a professor again. Why? To change this system of edutainment in chemistry.

Chemistry should be fun, but to a certain extent. If you want kids to actually learn, you need to teach them important concepts, not just show them the latest and greatest sexy experiments that have little experimental value. Basic skills, especially critical thinking need to be taught. Students should be challenged in labs, cause if they’re easy, what’s the point?

</insert 2 cents>

That’s my two cents. What’s yours?

By January 12, 2009 21 comments fun, general chemistry, opinion

Anti-Freeze and the Automotive Industry

My brother-in-law recently bought a new car with the intention of taking it with him into the Rocky Mountains in a few years.  Worried about sub-zero temperatures, he looked into modifying his coolant/anti-freeze system and learned about a new trend in the automotive industry.  An increasing number of suppliers have begun marketing propylene glycol as an alternative to the widely used ethylene glycol because propylene glycol has a lower freezing point than its two-carbon sibling.  A savvy chemist should instinctively think “freezing-point-depression,” a staple of freshman general chemistry lectures.  Mathematically, it’s identified by the following equation:

1

Wikipedia will inform you that freezing-point depression is a relation of the Clausius-Clapeyron equation and Raoult’s law.  Personally, I have not found use for either of these equations, and I’m not about to BS my way through the derivatives (pchem was not my strong point as an undergrad).  Anyhow, the above equation tells us that a pure compound’s freezing point will drop if you add another solvent to the solution.  For example, water typically freezes at 0 oC and propylene glycol freezes at 59 oC.  According to Sierra Anti-Freeze’s literature, a 2/3 mixture (by volume) of propylene glycol and water will start to crystallize at -4 oC, whereas a 3/2 mixture will begin crystallization at -54 oC.  In fact, the change in water’s freezing point is much larger with propylene glycol than with ethylene glycol. 

2Ethylene glycol is an interesting compound.  The majority of households know that anti-freeze (i.e. ethylene glycol) is highly toxic and that dogs like to drink it.  Upon ingestion mammals digest ethylene glycol by oxidizing it to oxalic acid (among other compounds), which has been linked to kidney failure.  Ethylene glycol purportedly tastes sweet to humans and dogs, which has prompted manufactuers to begin adding a bittering agent.  C&EN covered the issue a couple years back and from what I’ve recently read only Maine, Arizona, New Mexico, California and Oregon require bittering additives by law; Wisconsin’s right behind them.  For whatever it’s worth, the bittering agent (denatonium benzoate) is sold commercially as Bitrex or Aversion and is added to products such as rat poisons to prevent human consumption.  By comparison, propylene glycol is generally regarded as a safe, non-toxic chemical.

If propylene glycol is safer and appears more advantageous than ethylene glycol, why does the auto industry use it?  I couldn’t find an answer.  I did learn that some automobile manufacturers will actually void your warranty if you do not use their “approved” anti-freeze (usually ethylene glycol). Perhaps this issue will be addressed by the Obama-appointed US car czar in January. 
 

By December 28, 2008 11 comments general chemistry

Halogen Bonding

Some of you may be familiar with the term “halogen bonding”. In analogy to hydrogen bonding, this weak interaction occurs between an electron donor, such as nitrogen, and a halogen (Cl, Br, I). The halogen acts as an electrophile.

Halogen Bond N...Br

This is possible because the halogen has a region of positive partial charge at its tip, the so-called sigma-hole, as shown by calculations (doi:10.1007/s00894-006-0130-2). The group of Resnati and Metrangolo in Milan have used this interaction to construct a variety of polymeric chains and networks for crystal engineering. As they discuss in their current Science paper (doi:10.1126/science.1162215), it also plays an important role for drug design, which I am particularly interested in. Many drugs on the market are halogenated aromatics. The exact role of the halogen for binding is not always known, since often it was introduced in order to tune the hydrophobicity of the compound. I suspect that in many instances, halogen bonding to a backbone carbonyl oxygen could be of importance.

Clearly, more work is required to further investigate halogen bonding in a biological context. If people want to incorporate this kind of interaction into rational drug design or crystal engineering, good quantitative models will be needed.

By August 23, 2008 14 comments general chemistry

Thermite Bullets

In the most recent issue of X-men, issue #193 Jan. 2007, there is an interesting new bullet used to fight one of the main villains in the current story arc. The bullets are fired by Mystique and lob into the water-based bad-guy. See image below.

Technically Hydrogen is neither a product of the reaction nor is it a by-product produced when the reaction is ran in the presence of water. But, if enough heat is radiated from the reaction in a short enough time in the presence of water, then yes, any surrounding water will probably decompose to it’s constituent parts of hydrogen and oxygen gas. You can click the picture above to see the whole comic page to better appreciate the chemical implications of Thermite Bullets.

Thermite Chemical Equation
Fe2O3(S) + 2Al(s) –> Al2O3(s) + 2Fe(s)

For more thermite action check out the Brainiac special below. Just keep in mind, Brainiac has been known to fake its science videos (to popularize science) to the grave dis-service of the actual science.

Finally, you can blame excimer of the coronene bloggers for this, but after navigating Jim Tour’s website a bit more thoroughly I’ve discovered an interesting audio file of Tour explaining his adventures of collecting Porn magazines from gas stations and the pervertedness of homosexuality. Link to file: The True Meaning of Manhood
How the hell can professors keep making these derogatory comments with impunity?

Note 1: Thermite does not detonate! Maybe HMX can cover the process of detonation and what it really involves as a guest blogger one day.

Mitch

By December 13, 2006 0 comments general chemistry