Friday, January 30, 2009

Fun with Measurements and Molecules

Here are a couple of fun links for Friday.

First from Neatorama, a list of Fun and Unusual Units of Measurements
Some of these are just plain silly, but there are a few legitimate chemistry-related units too, including Avogadro's number, Scoville heat units, and alcohol proof.

And also by way of Neatorama, a link to some Molecules with Silly of Unusual Names
These are all actual molecules, although some of the names might be considered more like nick-names (i.e. not the systematic, or most commonly used common names.)

I rather like penguinone - a ketone that looks vaguely like a penguin.  I'll have to share it with my daughter who is currently fixated on Club Penguin.

Wednesday, January 28, 2009

Biodiesel from Coffee

ResearchBlogging.orgI don't often think about fat in my coffee (unless you like to add cream to yours - I prefer not to dilute my coffee.) If you consider that a coffee bean is just a seed for the coffee tree, it's not so surprising. The growing plant needs food and fat is a pretty good source of calories. You can see for yourself what the fat content in coffee is: the USDA has an online database you can search for nutritional info. Do a search for coffee - I chose the listing for:
Coffee, brewed from grounds, prepared with tap water
For a one cup serving, there is about 50 mg of fat, most of which is listed as "18:1 c" which means there are 18 carbons and one double bond in the fatty acids present, with a cis double bond.  The common name for this fatty acid is oleic acid.

By way of Greg Ladens blog, I came across a paper describing how Biodiesel can be obtained from coffee grounds.  Greg's post discusses some of the more practical aspects - and possible problems - in coffee being an economically useful source of Biodiesel.  I want to talk about the chemistry involved.

Spent Coffee Grounds as a Versatile Source of Green Energy describes how Biodiesel can be obtained from used coffee grounds.  Specifically they got their used grounds from Starbucks, probably a good source.  According to the paper, the used coffee grounds yielded about 15% oil which compares favorably with the yields from soybean oil and palm oil.  

So just how to you get biodiesel from coffee grounds? Surprisingly you start the same way you would if you were brewing coffee. However instead of using water, they "brewed" the used grounds with an organic solvent which would dissolve any oils remaining in the grounds. They tried three different solvents: hexane, dichloromethane and ether.  In addition to the oils, they also obtained Free Fatty Acids (FFA's), which had to be removed before they could convert the oil to biodiesel.  Hexane extracted the least amount of FFA's, so that was the solvent they chose to use.

The grounds were separated from the solvent-and-oil mixture by filtering it - again, just like brewing coffee.  The solvent was evaporated and collected for re-use and the FFA's removed from the crude oil by extracting with water and base.  This effectively converts the FFA to soap which is water soluble and can be separated from the non-water-soluble oils.  The FFA's have to be removed for two reasons.  
  1. FAA's are typically solids, or become solids at temperatures you might experience while driving.  Oleic acid has a melting point of 13-15 degrees C, that's about 57 degrees F.  Having your fuel become a solid in the fuel line or engine would probably be inconvenient.
  2. The method they use to convert the crude oil into biodiesel would not work on FFA's.
You could use the straight oil to run a diesel engine without doing anything else.  In fact, Rudolf Diesel did experiment with vegetable oils in his engine. Usually, the straight vegetable oil is converted into the methyl (or ethyl) ester and this is what is meant by "biodiesel."  The main reason for this is that the methyl ester is less viscous and stays liquid at a lower temperature than the straight vegetable oil does.

Biological fats and oils are triglycerides, which consist of a molecule of glycerol and three fatty acid molecules joined together to form a single molecule that is a triple-ester.  In making biodiesel, a transesterification reaction replaces the glycerol triple-ester with three molecules of methyl ester.

As any organic chemistry student could tell you, the transesterification reaction needs a catalyst and both acid and base will work as the catalyst.  If they had used an acid as their catalyst, they would probably not have needed to remove the FAA's, because under acidic conditions the FFA's would also have been converted into the corresponding methyl esters.  Under basic conditions the FAA's become soap instead, which is even less useful in your engine than the straight FFA.

So why did they use base as the catalyst?  The reaction is faster with the basic catalyst than with the acid catalyst, see this paper for a comparison of the two catalysts.  There might be other practical reasons, too.  KOH is a solid and not volatile. Although the KOH dust is corrosive, it is probably more convenient to handle and spills could be swept up.  Sulfuric acid would be handled as a liquid, it produces corrosive vapors and any spills would much more trouble to clean up.
Cool Google tip:  Google will calculate unit conversions for you.  I got the melting point for oleic acid from Wikipedia, which gave the mp in celcius. While I use celsius all the time in the lab, I'm not so familiar with thinking about celsius in terms of weather forcasts, so I converted it to Fahrenheit.  And I didn't need to look up the tedious equation since Google can do the work for me.  In the google search box type: "14 degrees C in F"  without the quotes and hit return.  Google will reply with: "14 degrees Celsius = 57.2 degrees Fahrenheit"

Narasimharao Kondamudi, Susanta K. Mohapatra, Mano Misra (2008). Spent Coffee Grounds as a Versatile Source of Green Energy Journal of Agricultural and Food Chemistry, 56 (24), 11757-11760 DOI: 10.1021/jf802487s

Monastic Musings: How can I be failing? - Unskilled and Unaware of It

A while back I found this article over at

Monastic Musings: How can I be failing? - Unskilled and Unaware of It In this post, Edith osb writes:
I noticed a surprising phenomenon last semester. Several first-year college students were getting consistently low scores on chapter quizzes - and they did not seem the least bit bothered or concerned about it. They were similarly unperturbed about scores below 60% on the first exam. When they received their mid-semester grade report, though, two of them came to see me, astounded to get such low grades. Their surprise was, of course, surprising to me: how could they possibly think that they were doing well when their quiz and exam scores were in the 50% to 60% range? They claimed that they were unaware that they were doing so poorly, and were somewhat angry that I had not "told them sooner."
A few years ago I had a student come to see me after final grades had been turned in.  The student had failed the class and was in tears, "Is there anything I can do to improve my grade?"  I was stunned, and explained that it was too late. Final Exams were the week before and the semester was over.  I gave 4 midterm exams and a Final Exam, this student had failed every one of them.  How could you not realize that you were failing the class?  Each of those exams was a clue that the student needed to get help.

I have always felt that college students should be treated like responsible adults.  It is their job to pay attention to their grades and get help when they need it. But reading Edith's post, and the article that inspired it, I am reminded of how easy it is to fool yourself.  I was not a particularly good student as an undergrad, and I often reassured myself that I would do better on the next exam - this did not tend to happen.  Realizing that you need help is difficult, and asking for it can be even harder still.

But there may be something else at work in addition to rationalizing and avoiding things that are difficult or uncomfortable.  In "Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments," Kruger and Dunning are interested in how people judge their own abilities. They looked at four different studies where the subject was given a task to complete, and then asked to predict how well they did.  

All of the subjects in all four studies tended to rate their own performance as above average! (How can everyone be above average?)  The subjects with the lowest scores thought that they had done much better that they really did.  The subjects with the best scores still rated themselves as above average, but generally below their actual scores. From this, the authors conclude:
We propose that those with limited knowledge in a
domain suffer a dual burden: Not only do they reach mistaken
conclusions and make regrettable errors, but their incompetence
robs them of the ability to realize it.
In the case of chemistry students, for example, this means that the students who don't know what they are doing also don't realize that they don't know what they are doing.  It is almost impossibe to correct your mistakes if you don't realize that you are making mistakes in the first place.

Consider American Idol.  If you have ever seen any of the audition shows you can see this in action.  The really awful contestants usually have no idea how bad they are, not a clue.  And they don't understand why the judges don't give them a ticket to Hollywood.  In contrast, a lot of the really good singers are much better at judging themselves reliably.  They know they sing well, but don't tend to over-estimate their ability.  They are often much better singers than they think they are, and seem a little surprised when the judges like their performance enough for a ticket to the next round in Hollywood.

Back to Edith's post.  She and some of the commenters suggest that some High School students - for a number of reasons - may not get trustworthy feedback on their academic skills, and because of that are not able to tell good work from bad.  They haven't learned to tell the difference. Or don't realize that it matters.

I have tended to downplay letter grades during the semester  - many things affect a student's final grade and one bad exam score can be offset by the remaining exams, quizzes and laboratory grades. I can't really predict a student's grade until everything has been graded.  I have also worked from the assumption that the student can tell that a exam grade below 70% means a D, which is close to getting an E (my school doesn't give F's, maybe the letter E is a little less judgemental) and realize that unless they do something about it they will be disappointed with their final grade. 

I think I may change that practice and start putting letter grades on exams and quizzes to help the low performing students learn to recognize unambiguously that they are not doing as well as they would like. I highly recommend reading both Edith's post (and the comments) as well as the original paper itself.

Saturday, January 24, 2009

Tom Petty Finds Some Ancient Tech

Been away for a while, so I thought I would post something fun.  What is all that weird stuff the band finds in the desert, all wrapped-up in plastic?  And aren't they watching Battlestar Galactica, too?