When Chemists Attack

I have often joked that, in addition to fume hoods, chemistry laboratories come equipped with giant invisible brain vacuums mounted above the door. These giant vacuums suck the common sense right out of students’ heads as they walk into the laboratory.

How else can we account for the fact that many students lose all common sense while they’re in the lab?

Here’s an example. We’re performing a specific heat lab in my introductory chemistry lab. Students heat up a metal sample by placing it into a test tube suspended in boiling water. Since the water is boiling, the metal evnetually reaches the same temperature as the boiling water: 100^oC. The metal is then put into a cup which contains a known amount of room temperature water. The students then measure how much heat goes from the metal sample to the room temperature water.

The lab manual asks students a queston: Why is the metal sample placed into a test tube and then lowered into the boiling water rather than being placed directly in the boiling water?

Putting the metal sample directly into the water – obviously – gets it wet. Transferring hot water along with the metal sample to the cup will make the temperature inside the cup go up more than expected, and the energy calculated will be too large.

One student had some trouble with the answer, and asked for a hint. But the problematic part of the answer might not be what you think …

Me: So, how is the metal sample going to be affected if you put it directly into the boiling water instead of the dry test tube?

Student: I don’t know.

Me: Okay. Hmm … Let’s say you’re riding in a boat and you fall overboard. What do you get?

Student: You get … tired? From swimming?

Me: How about this? You jump into the pool. How are you different after you jump into the pool from the way you were before you jump in?

Student: You’re … wet?

Me: Good. So now all you need to think about now is how that metal sample being wet with hot water before you put it into the cup would affect your results.

A post over at Pooflingers Anonymous reminded me of a little rant I’ve been meaning to post for a while.

Consider this lovely Pasteur pipet.

The Pasteur pipet is truly a small wonder. It’s cheap, disposable, and can be used to transfer small amounts of liquid from one place to another with almost no mess. The suction from the bulb keeps the liquid inside from dripping. There’s also very little risk of contamination of sample, since the glass part is disposable – and is only used to transfer one solution.

What irritates me to no end in introductory labs, though, is one simple error that students will just keep on making over and over again – no matter how many times I point out the error and correct it. That error is …

… holding the pipet with the tip up.

Holding the pipet this way causes the liquid inside the pipet to run down into the rubber bulb. While the glass body of the pipet is essentially chemically inert, the rubber bulb is not. Strong acids attack the bulb, as do many solvents – and the products of these reactions get into the dispensed liquid. Any contaminant that’s present in the rubber bulb – usually caused by some other student holding the pipet with the tip up – will also get washed into the dispensed liquid.

All of these contaminants will screw up results. For students, that translates into bad grades. That, at least, is something that students should understand!

Here’s one of my pet peeves – “preformed”. I routinely have students tell me things like

The standardization of 0.1 M base was preformed using the primary standard grade KHP.

I’m sure the student didn’t mold the base into a predeterimined shape before doing the analysis. Perhaps this student meant that they “performed” the standardization?

Of course, even the word “perform” in a description of what you’re doing in a lab is never actually necessary – unless you’re actually performing your experiment before a live studio audience. What’s wrong with saying sometihng like this?

The 0.1M NaOH solution was standardized by titrating against primary standard grade KHP.

CNN is carrying a small story pointing to a report from the National Research Council on science education for young people. The press release is here.

I haven’t had time to read the full report (352 pages!), but this part of the press release resonates wilh me (bold added by me, for emphasis).

Today’s standards are still too broad, resulting in superficial coverage of science that fails to link concepts or develop them over successive grades, the report says. Teachers also need more opportunities to learn how to teach science as an integrated whole — and to diverse student populations.

A little while ago, I was briefly involved in a workshop whose goals were to try to align the courses of the high school with the courses at the college – making it easier for the high schoolers to transition to our college when they graduate. This gave me some opportunity to talk with some of the high school teachers about what sort of things were in the standards to be covered in high school science classes.

While this National Research Council is about K-8 education, I find that the high school standards suffer from the same problems: too many topics and too few underlying principles. In the mad rush to get through all the bullet points the course is supposed to cover, important concepts receive rather shallow treatment. I remember remarking at the workshop – “Wow, if my freshmen actually understood half of what’s in that list [the standards], all I’d need to do in class is pass out the test.”

My incoming students might have heard the terms “chemical reaction”, “percent yield”, and “equilibrium” Were Alex Trebek to uncover a definition of percent yield on an episode of Jeopardy, many of my incoming students might respond with “What is percent yield?” But they aren’t able to connect these concepts – because they do not see chemistry as a set of ideas linking things together. And, they don’t see science as a way of getting things done. Instead of knowing science, they know Jeopardy.

The National Research Council recommends, for K-8 students, this:

Students should have a wide variety of learning experiences in science classes, the committee said. Those experiences should include conducting investigations; sharing ideas with peers; talking and writing in specialized ways; and using mechanical, mathematical, and computer-based models. Science should be presented as a process of using evidence to build explanatory theories and models, and then checking how well the evidence supports them.

Sounds good to me, but I have my doubts as to whether a lot of this will be implemented. It’s all a matter of cost. All the stuff suggested above costs money – not just in terms of technology, but in terms of personnel. I teach classes for adults who wish to work in the chemical industry – and I try to do a lot of the stuff above with them. For it to work well, the class needs to be small – so you can have meaningful interactions with students on the concepts they’re investigating. You also need adequate technology. For schools that have trouble keeping the buildings from falling apart due to lack of funds (read: poorer districts in my state, for instance), this’ll be a tall order.

Real science is better, but Jeopardy is a lot cheaper. At least in the short term.

News from the department of the obvious: Basic medical instructions hard for most adults, study finds

The subject of the article is how folks have trouble following “health instructions”, which is … not surprising in the least. We do pretty poorly in many areas of science literacy – medical science certainly isn’t an exception.

But here’s the quote that I’m going to fuss about, since I’m your friendly neighborhood chemist.

A consumer may want to know the salt content before buying, but the word salt isn’t on the label.

“Of course, they wrote ‘sodium,’ but that’s a technical term, that’s a chemistry term,” [Dr. Rima] Rudd said. “You don’t sit at the family table and say, ‘Pass the sodium please.”‘

Well of course you don’t ask someone to pass the sodium at the dinner table. Pure sodium is a soft, metallic element that reacts violently with water. It would be a decidedly bad thing to pass around at the family table. The stuff you pass around at the dinner table is a sodium-containing compound called sodium chloride.

Plus, “sodium” is hardly a more technical term than “gold”, “silver”, “iron”, or “oxygen”.

“They’re writing things at a level in the health field that is very difficult for the general public to work with,” Rudd said.

While I’d certainly agree that information leaflets that come with prescription drugs are written in a language that is difficult for someone without medical training to understand, I do not think the same thing applies to “sodium” on the side of a soup can. Anyone who makes it out of high school without enough knowledge to know a few basic things about what common table salt contains has been done a disservice.