Archive for March, 2008

OpenOffice.org 2.4.0

Friday, March 28th, 2008

OpenOffice.org recently released the 2.4.0 version of its free office software. I’m a Linux user, so I’ve used OpenOffice for years on my own machines.

There’s a Windows version, but I’ve always been hesitant about replacing Excel on our lab machines with OpenOffice Calc. Why the hesitation? Excel had one feature that OpenOffice Calc did not. A small feature, but one that saved my students a lot of time.

We don’t have anything in our lab that requires Excel, and our students usually use Excel for simple plotting of calibration curves. Excel could do simple regression analysis on the data and with one or two additional clicks, print a chart that included the regression line and its equation.

OpenOffice.org could print a chart that included a regression line, too. The problem was the equation. To get the equation of the regression line, you had to redo the regression somewhere else in the spreadsheet. If you wanted the equation of the line displayed on the chart, you had to manually type the equation onto the chart as a subtitle. This added a lot of extra steps to what should have been a simple one-click process. I teach chemistry, not computers. Wrestling with software to get it to do something that should be simple is a waste of my time.

That’s finally changed with OpenOffice 2.4.0. it’s now easy to display the equation on a chart, as you can see below.

[Regression line AND equation: OpenOffice 2.4.0]

… so now I should be able to use OpenOffice in my student labs. And if you haven’t looked at OpenOffice for data workup in student labs, check it out. It’s one less piece of software for your school and your students to buy.

Posted in Science education, Technology | Comments Off on OpenOffice.org 2.4.0

Live by the spreadsheet, die by the spreadsheet

Wednesday, March 26th, 2008

There’s a simple relationship that we use quite a bit in analytical chemistry: the relationship between how concentrated a solution is and how much light it absorbs. It’s called Beer’s Law, and in simplified form, it looks something like this:

[A = kc]

… where A = Absorbance (measured by a spectrometer), c = concentration, and k = a constant***. Even if you’re not familiar with Beer’s Law or the instrument it’s used with, you can see that this is a simple linear relationship. If you know the value of the constant k, then you can measure the absorbance of a solution on the spectrometer, then use the equation to find out how concentrated the solution is.

So how do you get the constant? Just make some solutions where you already know the concentration, and measure the absorbance of each one with a spectrometer. The raw data looks something like this.

Test Tube Concentration (M) Absorbance
1 0.0100 0.25
2 0.0150 0.38
3 0.0250 0.63
4 0.0450 1.13
5 0.0600 1.50

Now, what would you do to find that constant, k, that relates the absorbance and the concentration? Here’s a hint – you’ll need to plot the data and perform a linear regression analysis to find out the value of k. This might sound hard, but a modern spreadsheet can make a nice looking plot and perform the linear regression. All you have to do is enter the data, tell the spreadsheet what things to plot, and let the spreadsheet do the grunt work.

Some of my students had to plot absorbance and concentration data as part of a recent laboratory experiment. A depressingly high percentage of these students produced this plot.

[The wrong plot]

Quick! What’s wrong with this plot? (And no fair peeking below to see the answer!)

After making the plot, these students used the value for k that the spreadsheet calculated to find the concentrations of their unknown samples … and failed miserably – reporting concentrations that were several orders of magnitude too high. Impossibly high.

So where did the students go wrong? Their plots should have looked like this.

[The right plot]

Beer’s Law, after all, is a relationship between absorbance and concentration, not between absorbance and the numbers arbitrarily assigned to each test tube for identification! To further the problem, many of these students did not even notice that the concentration numbers they reported were ridiculously wrong.

I’ve been teaching freshman chemistry full-time for more than seven years, and this sort of mistake is much more common now than it was seven years ago.

James Cameron was wrong. The machines will take over eventually, but not via squads of semi-indestructible Schwarzeneggers. They will simply rob us of our ability to think.

*** This constant depends on several things, including the identity of the substance you’re analyzing and the size of the spectrometer’s sample holder.

Posted in Science education | 1 Comment »

Millions of words …

Tuesday, March 25th, 2008

Hillary Clinton is in a bit of trouble these days. While she said she had to run from an airplane to avoid sniper fire in Bosnia, video showed her calmly stepping off the plane and being greeted by officials and a young girl. The young girl then read Ms. Clinton some poetry.

Oops!

Here’s what Clinton said when being confronted about her fabrication.

“I say a lot of things — millions of words a day — so if I misspoke, that was just a misstatement,”

Over at Steve Benen’s blog, a commenter makes an observation about Clinton’s statement.

UM, can someone really find the time to say “millions of words a day?”
Am I the only one that finds it sad, funny and ironic that she manages to exaggerate in a statement meant to forgive her for exaggerating?

Sad, funny, and ironic. Check. I’ll focus on the “funny”.

So I got to thinking – how long would it take to say a million words? To give Clinton the benefit of the doubt, I’ll choose a small word that can be said quickly. Let’s say … “fart”. I can manage to say the word “fart” about three times per second if I don’t have to take a breath. If I didn’t have to take any breaths, then …

[92.6 hours]

… I’d get out the millionth word after well over three days. If I didn’t have to stop for a breath. And if I did nothing but say the word “fart” over and over for all 24 hours of each day. (A politician’s life is hard …)

How fast would Clinton have to talk to get out a million “fart”s in a day?***

[11.6 words per second]

11.6 words per second. If Clinton’s run for the presidency doesn’t work out, she can always replace this guy in the next series of Micro Machines commercials!

***This calculation hinges on what the definition of “is” a day is. Clinton may have been planning to speak from Venus, where the day (depending on which kind of day you mean) is either 243 or 117 Earth days long.

Posted in Politics, Silly stuff | 2 Comments »

Plug it in, plug it in.

Thursday, March 20th, 2008

I’ve been driving the same car for quite some time, now. It’s not that I can’t buy a new car. It’s more that no automaker wants to sell me the car I would like to buy. In the years since I bought my current car, the price of gasoline has soared, yet most of the current offerings from the major auto makers are no more fuel efficient than the car I already own.

The way I see it – with my commute to and from work, I shouldn’t even need to use any gas. My commute is about 15 miles each way.

If I’m going to take the plunge and buy a new car, I want something more than just a slightly less gas guzzling car than I have now. In short, I’d like a plug-in hybrid. It’d be a good deal more efficient, and it might even be less polluting – since it’s a lot easier to control emissions from one large source (a power plant) than it is from lots of tiny, separate sources (like individual gasoline engines).

It’s too bad that no one will sell me one.

C&E News has an article that surprised me a little.

The Department of Energy lab study assumes that by 2025, one-quarter of U.S. cars will run on a combination of electric and liquid fuels and will require plug-in charging. If all cars are charged at 5 PM, when electricity demand is high, some 160 large power plants will be needed nationwide to supply the extra electricity, according to the study. However, it says, if the charging is done after 10 PM, when demand is minimal, as few as eight—or possibly no—new power generation facilities will be needed, depending on the availability of regional electricity.

I’d assumed that putting lots of plug-in cars on the road would mean that lots of new power plants would be needed rather quickly. Apparently, that’s not the case as long as these cars designers make them default to charging during off-peak times.

So, automakers … where’s my plug-in hybrid?

Posted in Technology | 2 Comments »

It all depends on your point of view

Tuesday, March 18th, 2008

Recently, the EPA announced some new ozone standards, lowering the allowable amount of ozone pollution from 80 parts per billion to 75 parts per billion. That doesn’t sound like a lot, and indeed the EPA’s scientists recommended a much tougher ozone standard – from 60 to 70 parts per billion:

Nearly a year ago, EPA’s Clean Air Scientific Advisory Committee reiterated in writing that its members were “unanimous in recommending” that the agency set the standard no higher than 70 parts per billion (ppb) and to consider a limit as low as 60 ppb. EPA’s Children’s Health Protection Advisory Committee and public health advocates lobbied for the 60-ppb limit because children are more vulnerable to air pollution.

EPA and other scientists have shown that ozone has a direct impact on rates of heart and respiratory disease and resulting premature deaths. The agency calculates that the new standard of 75 ppb would prevent 1,300 to 3,500 premature deaths a year, whereas 65 ppb would avoid 3,000 to 9,200 deaths annually.

There’s a bit of a scandal here, since the Bush administration forced the EPA to go against its own science and issue less strict ozone standards.

So the new standard is too lax and fails to adequately protect public health. But it’s better than nothing, right? Maybe. If you’re a lobbyist for the chemical manufacturing industry, you might think that even the old 80 parts per billion standard was too restrictive.

“The available science is largely unchanged since the 1997 standard was issued and demonstrates that there is no clear and substantial basis for making the standard stricter at this time,” [the American Chemistry Council] said in a statement. Lowering the ozone standard “unnecessarily will impose significant new burdens on states and others even as they continue to try and comply with the 1997 standard.”

It all depends on your point of view.

Posted in Politics, Science | Comments Off on It all depends on your point of view