Archive for the ‘Challenges’ Category

Experimenting with Food

Thursday, April 5th, 2007

I know making geysers by adding Mentos to Diet Coke is soooo 2006, but bear with me for this one. A couple of months ago, I gave a small talk that was sidetracked for 15 minutes while the room discussed the subject. The second-most embarrassing aspect of the story is that I was responsible for leading us into the tangent, and the most embarrassing aspect is that, at one point, I minimized PowerPoint and opened YouTube to show a video of the phenomenon.

I was surprised to learn that many people in the room hadn’t even heard of the experiment. The set up is simple: take a 2 L bottle of your favorite carbonated beverage and several Mentos breath mints. As soon as the mints fall into the liquid, you get an instantaneous violent eruption. The more mints you add, the more violent the explosion. You can check out videos here and here.

From what I understand, there is no chemical reaction taking place—just the physical process of carbon dioxide being outgassed from solution. For some reason, the Mentos brand of mints provide especially nice nucleation sites for the CO2 bubbles to form. I’ve always heard that diet sodas are best for this demonstration because they aren’t sticky (making the clean up easier), but the other solutes (sweeteners, caffeine, etc.) appear to be important, too. These compounds alter the surface tension of the liquid, affecting the solubility of the gas and how quickly it can be released. I understand Mythbusters ran a number of “scientific experiments” on these geysers, but I’d like to see a hardcore experimental physicist get in on the action. It seems like there’s plenty of science left to be done.

In another example of YouTube science, people supercooled bottles of water (or beer) in a freezer and then shock froze the liquids. This involves cooling the liquid below its freezing point, which can be done if you handle the bottle gently enough. When the supercooled liquid is shaken or tapped, it quickly and spectacularly freezes over. I’m told by someone who has studied this phenomenon that it’s unclear what exactly is going on. Maybe the bubbles that are produced from the tapping provide the initial nucleation sites for the crystals to form? It might be similar to the process of selective flocculation used to purify potash salts. In this technique, a surfactant is added to a concentrated solution of the raw mixture of salts extracted from evaporite mines and bubbles are passed into the solution. I’m not sure whether pure crystals form at the air-water interface or if suspended crystals are simply swept along by the bubbles, but the “floc” floats to the top where it is skimmed off and sold. I’d like to see if the shock-freeze experiments work when there’s no air in the bottle, minimizing bubble formation.

Anyway, it seems like there’s a limitless supply of interesting experiments here that could engage high school students and get them to do some real science. It reminds me of the materials chemist who showed that M&Ms pack more efficiently than gumballs. This ground-breaking study merited a Science paper and extensive coverage in the news media (NY Times, CNN, etc.). While you may lament the publication of this paper in such a respected journal, we chemists need to do a better job of engaging the public and convincing them that “chemicals” ≠ “bad”. Undertaking studies involving food and other brand-name products might just help with that.

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Better Killing Through Chemistry

Thursday, March 22nd, 2007

Whether you like it or not, one of the principal reasons the government supports scientific research is to strengthen our ability to wage war. Scientific discoveries often open avenues for new and improved weapons, and making sure that our military technology is the most advanced in the world is vital to our national security. While military power alone is not a sufficient condition for maintaining our superpower status, it is a necessary condition. Part of our job as scientists is to use our knowledge to ensure that the “good guys” have the most advanced technology in the world when it comes to efficiently killing humans. Yes, this thought is a little revolting, but having scientists collaborate with the military is one of the best ways to ensure the protection of our political and social ideals.

The announcement that the US will begin developing a new model of nuclear warhead seemed to completely bypass the major news outlets. At least, no one made a fuss about it. I don’t know how much of an improvement the new design is over the old one, but it seems that the change is oriented more toward safer handling than greater yields.  That said, I wouldn’t be surprised if there’s more to the story.  I don’t expect the Army to go around advertising what exactly they’re hoping to accomplish. Congress needs to know, but that can be done behind closed doors. Suffice it to say, if the leap is significant, I think that the money used to fund the project would be money well spent. It will be interesting to see what Congress has to say when hearings open this month.

I’ve always wondered where the US stands in terms of the active development of chemical weapons. I know the Army has publicized the fact that it’s trying to destroy large portions of its stockpile, but it probably doesn’t want anyone to know whether it’s researching ways to create more potent chemical weapons.  Whether for tactical or strategic purposes, I simply presume that in some secret lab, the government continues to sponsor research on lethal chemistry.

And that’s a good thing. Do you think the bad guys wouldn’t use a powerful chemical weapon if they had access to it? No way. In both times of war and of peace, we should constantly challenge ourselves to develop new and improved chemical and biological weapons so that: 1) they are available if we need them and 2) we can develop effective counterweapons in case the enemy makes them first. Saying that the development of weapons of mass destruction is wrong and pursuing a strategy of self-imposed ignorance will solve nothing. We can’t afford to let our enemies seize the initiative on any of these fronts.

If you don’t want to participate, that’s understandable—I personally wouldn’t like testing compounds on mice all day—but be glad (as I am) that there are people who have decided to work in these areas.

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Fun at the Center for Astrophysics

Monday, January 15th, 2007

One of the major objectives of Harvard’s new Origins-of-Life Initiative is to build a community of scientists who can draw on each other’s expertise to figure out how life started. This approach makes a lot of sense when you consider the interdisciplinary nature of the problem. I really enjoy the collegiality that the new program has offered; it’s quite refreshing. In our department (chemistry and chemical biology), each research group essentially exists on its own island. The chemistry professors at Harvard seldom collaborate with each other on research projects, and inter-group interaction is uncommon. We don’t have departmental problem sessions, organized chats about science, or student colloquia.

In contrast, the Origins program not only offers a full schedule of seminars, but also a number of informal “chalk talks” where incomplete research is presented and discussed among the students and professors who show up. The newest feature of the program is a series of “lab visits,” where everyone tours the laboratory of one of the other researchers in the program. Last month, we took a walk up Garden Street to Observatory Hill and the Harvard-Smithsonian Center for Astrophysics.

Most of the origin-of-life projects in astrophysics concern hunting for planets around distant stars. About 200 exoplanets have been discovered, and there’s a good possibility that their composition can be studied spectroscopically. The researchers are especially interested in finding Earth-like planets and signs of distant life. Right now, the limitations of their techniques make it very difficult to find any planets other than large ones that are close to their stars (so-called “Hot Jupiters”). It’s interesting stuff.

What amazed me about the visit was how astrophysicists have a completely different culture from chemists. The first thing that struck me was that although grad students had advisors, the student offices were located in a central building instead of in the research labs. I got the sense that the students had their own vibrant community in addition to their individual labs, which has definite advantages. It is always nice to have a diverse set of acquaintances who are willing to engage you in scientific discussions. When you spend all day in one research lab, you are often surrounded by people who are experts in the same area and think alike.

Much like chemists get classified into organic and physical, the astrophysicists divide themselves into observers, theoreticians, and instrumentalists. The observers’ research is mostly limited by the time they can reserve on the best telescopes. Getting telescope time is a highly-competitive process: only 1-in-4 proposals are allocated time on NASA’s land telescopes. That number shrinks to 1-in-7 for the telescopes in space. Some schools even sponsor telescopes so that their faculty will have priority on them.

Because resources are tight and government instrumentation is used to collect the data, NASA lights a fire under the butts of the observers by opening the data they requested to the general public a year after it is collected. That means you have a limited period of time to find something interesting before any nerd with an Internet connection can scoop you.

I love the openness of their system. There is no comparison in organic chemistry, where despite the fact that most of our research is funded with taxpayer money, we generally resist sharing our data with anyone until it is published. And once published, some people are still unwilling to grant outsiders’ requests for help or data. Would you be willing to scan your lab notebooks and post them online?

Finally, I thought I’d share one interesting piece of scuttlebutt from the astronomical community. The word on the street is that the slated “Return to the Moon” is not very popular among scientists and stands a reasonable chance of getting scrubbed if the Dems take back the White House in 2008. So if you we’re looking for one, that’s another reason to vote donkey in the next election.

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