Articles by: azmanam

Chemistry Lab Demonstrations: Check-In Day

*For more cool stories, pictures, and videos of chemistry demonstrations, click here*

I’m TA’ing an undergrad organic lab this semester, and in order to keep myself and the students entertained, I’m trying to have some kind of demonstration at the beginning of each lab.  The goal is to have the demonstration have something to do with the theme of the lab.  The first lab of the semester was this week.  On the first day, all the students do is check in their glassware.  The lab doesn’t acutally have anything to do with organic chemistry.  So that means the demonstration doesn’t have to have anything to with organic chemistry, right?

This week, I did my favorite demonstration, the oscillating clock reaction.  Formally known as the Briggs-Rauscher reaction, mixing three colorless solutions together creates a solution which oscillates between blue, amber, and colorless for several minutes.

The explanation for what’s happening is actually really complex.  I’ll quote from the University of Leeds website:

In the Briggs-Rauscher reaction reaction the evolution of oxygen and carbon dioxide gases and the concentrations of iodine and iodide ions oscillate.  The somewhat simplified mechanism of this reaction can be represented by the following overall transformation:

IO3 + 2 H2O2 + CH2(COOH)2 + H+==> ICH(COOH)2 + 2 O2 + 3 H2O           (11.1)

This transformation is accomplished through two component reactions:

IO3 + 2 H2O2 + H+==> HIO + 2 O2 + 2 H2O                              (11.2)

HIO + CH2(COOH)2==> ICH(COOH)2 + H2O                            (11.3)

The first of these two reactions can occur via two different processes, a radical process and a nonradical process.  Which of these two processes dominates is determined by the concentration of iodide ions in the solution.  When [I] is low, the radical process dominates; when [I] is high, the nonradical process is the dominant one.  The second reaction (eq. (11.3)) couples the two processes.  The reaction consumes HIO more slowly than that species is produced by the radical process when that process is dominant, but it consumes HIO more rapidly than it is produced by the nonradical process.  Any HIO which does not react by eq. (11.3) is reduced to I by hydrogen peroxide as one of the component steps of the nonradical process for reaction (11.2).  When HIO is produced rapidly by the radical process, the excess forms the iodide ions, which shut off that radical process and start the slower nonradical process.  Reaction (11.3) then consumes the HIO so rapidly that not enough is available to produce the iodide ion necessary to keep the nonradical process going, and the radical process starts again.  Each of the processes of reaction (11.2) produces conditions favourable to the other process, and, therefore, the reaction oscillates between these two processes.

You can read more about the reaction and learn how to do it yourself from about.com.

Here’s a video of the oscillating clock reaction.  No, this is not me from lab the other day.

By January 29, 2009 6 comments fun

Science Podcasts

I got a new iPod Touch from Sigma-Aldrich for Christmas this year (no, really).  Probably the best part is the wi-fi capabilities.  I tried keeping up with podcasts before on other iPods, but it was too much work to plug the iPod into the computer, transfer over the new episodes, and repeat.  Now I can grab the new episodes directly from the iTouch, and it’s awesome.  (btw, does anyone know how to subscribe to the podcasts so the iPod will update itself with new episodes automatically?)

Anyway, I’ve been surveying the chemistry podcasts over the past few weeks.  They’re great to listen to while running a column or doing other tasks that don’t require a lot of mental energy.  Most of the major journals have a podcast, as do most news outlets and some other random sites.  I’ll tell you about some of the ones I liked below the jump if you’re interested in giving some of them a listen.

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By January 26, 2009 7 comments fun, science news

Can chemical compounds be pluralized?

I wanted to extract a paragraph from an earlier post and open it up for further discussion.  When I was creating the chemistry dictionary file, one of the last things I did was apply the dictionary file to ASAPs of popular ACS journals.  Here’s what I wrote:

One of the biggest things I noticed during this vetting was the use of plurals in scientific writing.  Cyclopentenone is an actual compound and is in the dictionary.  If your research requires you to make a family of cyclopentenones, then the plural was probably not in the dictionary (it is now, though).  Although, that raises an interesting question: can you pluralize compounds like that?  Or is it more correct to say that a library of cyclopentenone derivatives was made?  Same thing with families of natural products.  Are they members of the brevetoxins?  Or are they more correctly members of the brevetoxin family of natural products?  I’m not sure I know the answer to that one.  One thing I do know is that I did not include plurals of elements.  Your 13C NMR doesn’t tell you that you have 2 carbonyl carbons.  It tells you that you have 2 carbonyl carbon atoms.

The ACS style guide (at least the 2nd edition) doesn’t comment explicitly on the use of plurals with chemical compounds.  What say you?

By January 10, 2009 5 comments opinion

On making a chemistry dictionary (Or: Why Excel and Macros are awesome)

I thought I’d take you on a little journey though the process of making a chemistry dictionary from scratch.  It’s a pretty good story, I think.

It started with searching online for chemistry glossaries.  I figured that would be a good repository of chemistry-related words.  And, as a bonus, their definitions could give me even more words to add to my list.  I copied the six or seven glossaries I liked into one long Word document.  It was a messy document.  Random lists of words.  Some with definitions, some without.  Mainly words that are recognized by the standard dictionary, but many words that were prime candidates for my list.

(rest of the story below the jump. It gets a bit technical in the middle… but keep with it for the cool pictures (click the images for larger versions) and a Christmas idea for your favorite ACS copy editor!)

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By December 19, 2008 10 comments Uncategorized