Pet peeves: Preforming an analysis

October 9th, 2006

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.

Posted in Science education | 3 Comments »

Down to their level

October 9th, 2006

It’s always interesting to know what your students are actually thinking. I have to admit, though, that sometimes I would really rather not know. Take this example, buried in the comments from a set of student surveys from a past semester:

[Rick] needs to come down to our level.

You might expect to hear comments like this from students in, say, sophomore level chemical engineering thermodynamics. Heck, I still have nightmares about that course. The comment above, though, was left for me by one of my introductory chemistry students. Introductory chemistry is the lowest-level chemistry course we offer – roughly on par with a high school course. It’s the lowest-level science course with a lab that we teach.

How low a level are we talking here? Here’s one of the questions from this course’s first test.

Determine the length of the line based on the ruler drawn below.
[image of a ruler and a line]

(Why ask about a ruler in an intro chemistry class? We discuss reading of measuring devices like rulers, graduated cylinders, and balances early on in the course – otherwise the students couldn’t really do much in the course’s lab. The ruler itself is mostly meant to connect a familiar measurement – what adult has never used a ruler? – to more unfamiliar devices like graduated cylinders and balances.)

I’m at a loss. Education isn’t like the limbo. It’s not about how low you can go. And, with this particular course, it’s not as if I can “come down” any more. At some point, the student has got to climb.

Posted in Education | Comments Off on Down to their level

Classics of Student Literature

October 6th, 2006

This is a collection of funny student answers from my first few years of teaching introductory chemistry classes at my college. All student answers are presented as the student submitted them to me – spelling and all. Enjoy!

It helps to know what science you’re in

Question: Briefly define chemistry.

Student answer: A systemic substanse study of matter.

Conservation of mass: When you do a chemical reaction, the total amount of mass remains constant.

Question: Briefly state the law of conservation of mass.

Student answers:

  • Mass is equal to volume. You mass something when in something. The weight how much holds or is.
  • Mass measurements can be precise or accurate. Precise ask how close are measurements to the same measurement and accuracy wants to know is it right, law wants to know can I do it again.
  • Mass is how much it takes up on an object.
  • Mass is the kilograms.

Fun with Marshmallow Peeps!

Picture a marshmallow peep floating in a beaker of water. This was sitting in front of the students when they answered the following question.

Question: Is the marshmallow peep more or less dense than water?

Student answer: No.

Fun with magnesium!

Magnesium metal burns in air with a brilliant (almost blinding) white flame and leaves a white ash behind.

Question: Describe as thoroughly as you can what happens when a piece of magnesium is burned in air.

Student answers:

  • When a piece of magnesium burn in the air it will not show a reaction b/c the air has less density and it will not burn throughly.
  • It would explore like firecrackers.
  • When a piece of magnesium burns, it gets hard and turns into a metal.

Fun with oxygen!

Students prepare molecular oxygen (O2) and investigate the effects of a pure oxygen environment on combustion. They observe that things burn more intensely in pure oxygen.

Question: How does the amount of oxygen present affect the rate of combustion?

Student answers:

  • In high oxygen things give off better reaction and combustion. Compared to low concentration of oxygen.
  • In high concentration of oxygen is faster than air.
  • Oxygen burns faster and in air it doesn’t burn.
  • The fire is more contense in oxygen. The oxygen speeds it up (fire, the burning).

Sulfur burns a with bright blue flame in a high concentration of oxygen and with a dimmer blue flame in air. The faster sulfur burns, the brighter the flame is.

Question: What evidence from the burning of sulfur confirmed your conclusion about the rate of combustion?

Student answers:

  • That the sulfur when heat was added to it. It just started crackling and burning and looked like kinda like a copper color.
  • It change from a powder form to a liquid form.
  • It turned dark and there was a liquid.
  • An environment with pure oxygen can reignite flame from embers, but low concentration can not. High oxygen content created more intense heat.

Fun with hydrogen!

Students prepare, collect, and burn hydrogen. Hydrogen burns rapidly with a loud popping sound.

Students collected hydrogen by bubbling it through a bottle of water. This works because hydrogen does not mix well with water (it’s “insoluble”) and is able to push the water out of the bottle.

Question: What physical property of hydrogen, other than it is less dense than water, allows it to be collected in this manner?

Student answers:

  • Oxygen.
  • Very reactive.
  • Because it’s lighter than air.
  • Its ability to mix with other gases “diffusion”
  • It’s a molecule found in air.
  • It is an element, reactive, and can burn and also a gas at room temperature.

You don’t get a “pop” from hydrogen combustion when you bring a burning splint over a bottle which has sat open for a full minute. The hydrogen is very light and escapes into the room.

Question: How do you account for this?

Student answers:

  • Because hydrogen is dense.
  • B/C it was left open for 1 minute + the hydrogen left out. Was oxygen.
  • Air and hydrogen in the bottle did not make a popping noise.
  • The hydrogen was at the top of the bottom.
  • Oxygen put out the flame.

Posted in Science education, Silly stuff | 6 Comments »

Friday Cat – Extremely late edition: Adrian!

October 2nd, 2006

[Ash]
Ash: Well, ya see, sir I understand you’re lookin’ for sparrin’ partners for Apollo, and I jus’ want ta let ya know that I am very available.

Posted in Animals | Comments Off on Friday Cat – Extremely late edition: Adrian!

Canadian bakin’

September 28th, 2006

Via CHEMED-L (the chemical education list), here’s an article on a recent Canadian drug bust.

Actually it’s only sort-of a big drug bust. The person charged had some marijuana plants, but the big news is that he was accused of:

selling and possessing “precursor chemicals” for meth

These “precursor chemicals” were the makings of, according to the article, nine million Canadian dollars of meth.

She said the seizure, the result of months of investigation, is the RCMP’s biggest ever in the national capital region.

“It is huge,” Beauchamp [of the Canadian police] said

The chemicals? Red phosphorus and iodine. (Stop laughing.)

Red phosphorus is one of the forms of the element phosphorus. White phosphorus is the other form. It’s nasty stuff, and you’d be well-advised to avoid it.

Red phosphorus, on the other hand, is usually considered non-toxic. Extremely flammable, but non-toxic. Got a match? Well, you’ve quite likely got red phosphorus.

Then there’s iodine. Well, iodine’s just neat stuff. However, it’s actually a lot more toxic than red phosphorus is, in pure solid form. Solutions of iodine, on the other hand, are commonly used as disinfectants – check your local drugstore or your medicine cabinet.

Without making any additional commentary on the various “wars on drugs” and their usefulness, I’ll just say this: If you want to bust someone for meth, bust them for actually having or distributing meth. Busting someone for “precursors”, many of which are extremely common substances, will not lead us anywhere we as a technological society want to go. (See here for what sort of things you could be considered a criminal for having in a certain large US state. Scroll down to see the silliest of the stuff.)

(Edited to add: Or bust the guy for having a ton of highly flammable material in a residential neighborhood, perhaps. But not because it’s a “precursor”.)

Posted in Science | 2 Comments »

Science education as Jeopardy

September 22nd, 2006

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.

Posted in Science education | 1 Comment »

North Carolina BBQ – Village Inn in Lumberton

September 21st, 2006

My never-ending quest to eat pork barbecue has recently taken me to Lumberton, NC. If you’re headed through Lumberton around dinnertime, you might want to stop and have a bite at the Village Inn Bar-B-Que and Seafood. Here’s what you can expect at the Village Inn

First, don’t expect fancy signs.

[Sign]
They don’t go for fancy neon signs at the Village Inn

Don’t expect a fancy building.

[Outside]
They don’t go for fancy buildings, either.

Do expect excellent hush puppies

[Hush puppies]
Share these with the other folks at your table!

Do expect a good-sized portion of North Carolina light vinegar barbecue, served with slaw and fries.

[BBQ plate]
This is the medium barbecue plate, which cost just under $6.

Don’t expect hash, since you’re in North Carolina.

Village Inn reminds me a little of the barbecue places I would eat at when I was a kid. Shabby cinderblock buildings, decidedly non-fancy decorations and menus, but good food.

[From the table]
No-frills eatin’

You can also get containers of hot or cold barbecue for take-out – just in case you need a shot of pork barbecue for the road, and it’s about as cheap as you’ll find anywhere. At Village Inn, you can get a few pounds of BBQ for what Maurice would charge you for a single Big Joe sandwich in SC.

If you want to try the Village Inn, you’ll find it at 3345 Martin Luther King Jr Drive in Lumberton. If, like me, you’re not from around there, exit I-95 onto highway 74, then follow 74 until you get to highway 21 (which is Martin Luther King Jr Drive). It’s just past the fairgrounds.

Posted in Food | 2 Comments »

Safety tip

September 21st, 2006

Dan Holden teaches middle-school socal studies class, and burned a small American flag to get his students to think and write about the flag-burning issue. The story’s here.

As this story takes place in Kentucy, you can imagine what happened. Kentucky has a law against flag desecration, but it’s likely unenforcable due to the Supreme Court ruling that flag desecration is protected speech. So how are the reactionaries going to try to punish Mr. Holden’s brazen attempt to … get students to think about an issue?

The district also alerted city fire officials, who are conducting their own investigation.

“Certainly we’re concerned about the safety aspect,”

Another article says, thankfully, that

… the evidence doesn’t warrant filing a charge of criminal wanton endangerment — causing significant risk of serious injury or death.

So, they were going to try to bust Mr. Holden for “safety” reasons. That’s pretty pathetic, in my book. But there’s a lesson to be learned from this:

If you’re going to burn a small American flag in an effort to get students to think about the flag-burning issue, then make sure to burn said American flag under a properly-functioning fume hood.

Posted in Education, The culture wars | Comments Off on Safety tip

F-in Hamburgers!

September 15th, 2006

Over the Labor Day holiday. we happened to walk by Johnny Rocket’s in Myrtle Beach, where they serve …

[F-in hanburgers]

… F-IN HAMBURGERS!

Having been in this restaurant before, I can tell you that the hamburgers they serve are f-in expensive, and that they don’t taste all that f-in good.

I have to appreciate the truth in advertising, though!

Posted in Silly stuff | 2 Comments »

The many phases of iodine

September 11th, 2006

Iodine is a rather neat element. It’s a nice – if a little boring looking – crystalline solid at room temperature. Chunks of iodine are similar in appearance to things you might find in the bins of rocks at places like Black Market Minerals at Barefoot Landing.

[Solid iodine]
Solid iodine

Iodine is interesting because it is easy to make solid iodine go into the gas state. Plus, unlike many gases, iodine vapor has a distinct purple color and is easy to see. Solid iodine slowly sublimes (goes from the solid state to the vapor) at room temperature. It’s easy to accelerate this process by supplying a little heat.

If the iodine vapor comes into contact with a cool surface, it will deposit (resolidify) on the surface, forming pretty crystals. (A similar thing happens when water vapor comes into contact with a cool surface, although in that case you usually get liquid water.)

To show this, I tried to replicate a picture of a demonstration from one of my older chemistry books. I took some solid iodine and put it into a beaker, then set the beaker on a hotplate. On top of the beaker, I put a watch glass (curved piece of glass that looks something like a lens) and some ice – to provide a nice, cool surface.

[Setup]
Setup

To speed up the production of iodine vapor, I turned on the heat (just a little). You can just barely make out the purple iodine vapor in the beaker.

[A little iodine vapor]
A little vapor is visible

If the hotplate’s temerature gets to about 114 oC (about 237 oF), the iodine will begin to melt, forming a dark purple liquid. The amount of iodine in the vapor state goes up, too!

[More iodine vapor]
More vapor is visible. If you value your nose, keep it away from this vapor.

What’s impressive about this demonstration is the sheer number of phase changes that are going on at once.

[Phases galore!]
Pick a phase, any phase!

At the bottom of the beaker, you have some solid and liquid iodine. Since the hotplate is providing heat energy, you have the solid iodine melting and subliming. The liquid iodine is also evaporating. Near the top of the beaker (and to some extent on the sides of the beaker – which are cooler than the bottom), you have deposition of iodine vapor, forming solid iodine crystals. (It also looks like some iodine may have condensed on the hotter parts of the beaker nearer the bottom, then frozen after the beaker was removed from the hotplate.) That about covers it!

… not counting the ice, that is. The ice at the top of the beaker is melting, removing energy from the iodine vapor as it deposits on the bottom of the cold watch glass.

[Deposited crystals]
Deposited iodine crystals, forming from purple iodine vapor

The crystals formed on the watch glass are flat and shiny – almost metallic in appearance. They’ve grown to look a bit like perverted stalactites.

[Deposited crystals, closer view]
Deposited iodine crystals, closer view

A few words of caution if you attempt this experiment yourself. Iodine may look harmless (it won’t blow up on you – provided you keep it away from combustibles), but iodine solid can cause chemical burns on skin contact, and iodine vapors are very bad for the lungs. This sort of experiment needs a fume hood, and solid iodine shouldn’t be handled directly.

Posted in Science, Science education | 2 Comments »

« Older Entries
Newer Entries »