When Chemists Attack

One of the many hats I wear here at the college is that of student adviser. On the surface, it seems a simple task; look at the student’s courses and make sure they stay on track for their major. But it’s less easy than it looks.

A colleague of mine was advising a student recently. I overheard, since all of the science department offices are clustered right next to one another. This student had declared nursing as a major, and had just finished our remedial English and math courses – making him ready to move on to introductory algebra and freshman composition and some freshman-level college courses.

To qualify for admission into the nursing program^***, however, this student still needs to take a four semester sequence of introductory anatomy, college anatomy, physiology, and microbiology. There’s a small wrinkle; he’s attempted the introductory anatomy course one time already and had to drop because he wasn’t doing well. One more poor grade would drop him into academic probation.

So, this student is looking at no fewer that eight semesters until he can graduate with an associate’s degree in nursing and become an R.N. It’s going to be a long road for this student. For many in similar situations, it is an impossible road. Most students who drop out of our simplest anatomy course for academic reasons do not make it into the nursing program, and fewer still actually make it through.

Still, though, everyone deserves their shot. This is one of the students that you put into his courses, warn him that his performance in these introductory courses will determine if he gets into nursing or not, and suggest that there are other programs – like surgical technology^**** – that he could get into and land a hospital job in year or so. And if he’s still gung-ho on nursing, you point out places – like the tutoring center – that will increase his chances of making it through his upcoming science classes.

So, my colleague starts figuring out what courses this student needed, and the student drops his bombshell. He wasn’t really interested in being a nurse. He was going to go to medical school and be a doctor. The nursing degree, he said, was just something to do until he became a doctor.

My colleague, sounding a bit surprised by the student’s revelation, suggests that the student might want to change his major to one of our degrees meant for college transfer. Most of the courses required to get an associate’s in nursing are specific to the program – and not accepted for credit at a university. At this point that the student becomes defensive and accuses my colleague of “being negative”. Apparently, the student doesn’t want to hear that the path they’ve chosen might not be the best way to reach his goal.

So what can you do with a student like this? Not a lot, I’m afraid. It makes me sad. This student sees us as an adversary – an obstacle they must jump over to reach his goal. That view will hurt him every time he steps into a classroom, and may very well contribute to his goals remaining forever out of reach.

^***Our school has an open-door policy. Essentially, anyone who wants to come out here can come. Individual programs do have entry requirements, though. Even so there are usually multiple ways to get into a program. For nursing, students who don’t score high enough on the SAT can earn their way into the program by completing their required biology and math courses. After they have proven themselves, they’ll be accepted to the program.

^****Surgical technology doesn’t pay as well as nursing, but it requires only a single anatomy course. Students who can’t handle the anatomy and microbiology requirements for nursing can often succesd in this program.

Take a look at this graph, showing college enrollment (in thousands of students) from the 1970s through 2005.

Source data: US Census Bureau

The red curve is what you probably expected. College enrollment increases fairly steadily with time. (The sharp dip in the late 70s is an artifact of changing the method of counting students).

But there’s a wrinkle. The red curve counts only undergraduates at four-year colleges. The blue curve shows the situation in America’s two-year colleges: community colleges, junior colleges, and technical colleges. Enrollment in our two-year colleges is flat, and has been so since the early 1990s. Before 1990, two-year college enrollment grew along with four-year enrollment.

Is the conventional wisdom that you need at least a bachelor’s degree to get any kind of worthwhile job now so entrenched that nobody thinks to go to a two-year school anymore?

Since I teach at a two-year school, the flat enrollment figures concern me. I worry that students who are perfectly capable of getting a two-year degree and a good job^*** are being siphoned off by four-year schools – who then proceed to chew many of them up and spit them out without either a degree or useful job skills.

So, why are two-year college numbers so flat? Your thoughts?

^***Who do you think has better job prospects? A new registered nurse with an associate’s degree in nursing, or someone who has just gotten their bachelor of arts in English?

Students love multiple choice questions. I typically have several types of questions on my
chemistry tests. If I tell my students that there will be only, say, fifteen multiple choice questions on the upcoming test, I will almost always have several students frown and ask for more.

Sometimes, I’m tempted to give in and just give a multiple choice test like these students want. After all, multiple choice questions are the easiest kind of test question to grade, and I don’t have any assistants to grade papers for me.^*** But I don’t give in. The reason? Because students almost always perform more poorly on multiple choice questions than they do on “harder” question types.

Why?

Some students will tell me that they like multiple choice questions because the right answer is already on the paper, and it’s easier to find the answer in a list than it is to figure the answer out. This might actually be part of the reason that students do so poorly on multiple choice tests: They don’t think that they have to figure anything out, and they expect multiple choice questions to be like this:

These charged particles are normally found inside the nucleus of atoms.
A) birds
B) cheeseburgers
C) oranges
D) orangutans
E) protons

… where the right answer is immediately obvious, even if you don’t know a darned thing about chemistry or the nuclear model of the atom. Instead, they get questions more like this:

These charged particles are normally found inside the nucleus of an atom.
A) borons
B) electrons
C) neutrons
D) photons
E) protons

This is still an easy question, but some students will miss it. These same students are able to draw a picture of and describe the basic details of the nuclear model of the atom in a later (not multiple choice) question on the same test! My conclusion is that the student misses the multiple choice question because he simply doesn’t expect to have to think about it.

I see the same thing with multiple choice questions that involve a calculation. If the same problem is presented as a multiple choice question and as a problem where they have to write their answer in a blank, the students will miss the multiple choice problem more often. They will try to do the multiple choice problem directly on their calculators (despite scratch paper being available), while they will usually write down the steps of the problem where they have to put their own answer in a blank.

In summary, if any students are reading this – don’t ask for more multiple choice questions! They’re not really “easier” than any other kind of question, and they’re more likely to bring your grade down!

^***Well, except for this assistant. But you don’t want her grading your paper!

Here’s one writer’s take on the state of biology education in schools.

[N]ot one in a hundred graduates of our public schools could state any evidence showing whether vaccination is beneficial or harmful, or describe how malaria, diphtheria, or yellow fever are acquired, and how they may be prevented.

The pupils have spent much time in learning meaningless words, but when information is sought concerning the evidence that typhoid fever is caused by drinking polluted water they remain silent. A pupil is rarely found who can state clearly how the fact has been established that bacteria produce disease. In consequence very many do not yet believe that disease is preventable, and so pay little heed to the laws made by the state for the welfare of its people.

Y’all could probably guess the time frame by the style of writing and the particular diseases named. The quote above was from Alvin Davison’s The Human Body and Health, written in 1908.

These days, I’d wager that closer to 99 in a hundred public school graduates do know that bacteria (and viruses) cause disease – and know that much disease is preventable.

The moral of the story? Whatever the state of our educational system, it’s never good enough for us. That’s no bad thing; we should strive to improve education. But – we need to keep things in perspective. Things are a lot better now than they were in the “good old days”!

I’ve often said to students that I’d rather be taking an exam than grading one. They sometimes stare back at me with jaws hanging open, shocked that I would say such a thing. In this post, I thought I’d take a brief look at a few of the reasons why grading an exam is harder than taking one.

Here’s a question from one of my recent exams for an introductory chemistry course.

Metallic aluminum (Al, FW = 26.98 g/mol) reacts with oxygen gas (O₂, FW = 32.00 g/mol) to produce aluminum oxide (Al₂O₃, FW = 101.96 g/mol). How many grams of oxygen gas are required to react with 14.7 grams of aluminum metal?

Based on the way I taught my students to solve this sort of problem in class (the factor-label method), I expected most students to come up with the answer 13.1 g of O₂ using a calculation procedure similar to this one:

But there’s a hitch! There’s more than one way to work this problem. Another way to solve the problem is to find out the mass ratios of aluminum to oxygen based on the chemical equation and set it up as a ratio:

Solving, x = 13.1 g of O₂.

This looks very different than the first way I showed to solve the problem. Though it’s not the way I taught chemical calculations, it’s a perfectly legitimate strategy for solving this kind of problem. To make it more … interesting, you can actually set up the ratios so that they look a little different from the way I wrote them above.

So, when you prepare to grade a test, you not only have to solve the problem the way you would have solved it yourself, but you also have to consider the problem-solving strategies your students might come up with to solve the problem. Otherwise, you won’t be able to see whether a student actually has an understanding of the material, and you won’t be able to help them correct any mistakes they made if you aren’t able to follow their strategies.

Think that’s bad? There’s another hitch!

Here is an actual student answer to the problem above.

8.72 g of O₂ is needed to react with 1.47 g Al

107.92 Al 96 O 53.96x = 440.4 8.72

14.7g Al = ___________ g O2 12.45

(Yes, the answer really did look like that on paper.)

Obviously, the student got the wrong answer. Equally obviously, this “solution” is a mess! But, is there anything we can work with here in the mess? Is there any help we can give the student so that (s)he might do better next time?

It’s very clear that the student wanted to try using the ratio method to solve the problem. Why? There are actually two attempts to use the ratio method in this answer. The attempt on the right would have actually gotten the student to the right answer, but the student makes a math error in the attempt and comes up with 12.45 g of O₂. Because the student doesn’t label what their numbers or letters represent, (s)he simply doesn’t realize that the value of x is the desired answer – and gets lost.

Once students start floundering in a sea of unfriendly numbers, they never end up anywhere useful. The wrong-on-all-counts ratio on the left-hand side of the page makes that point quite clearly. If the student had reazlied that the value of x in the ratio on the right was the desired answer, (s)he would have stopped at 12.45 g O₂. Still not correct, but only off because of a case of fumble-fingers with the calculator.

The advice this student needs to hear, I think, is that when solving a problem it is vitally important to keep track of what numbers and variables actually represent. In math class, students find x for x‘s sake. Everywhere else, x is merely a name for sometihng real. This is a point that I don’t think is made nearly strongly enough in math classes.

But back to the title of this post – how long did it take to sift through the student answer? Longer, i’d wager, than the student spent on the exam solving the problem. And that’s why grading an exam is harder than taking one!

The conventional wisdom says that you shouldn’t eat or drink anything that students might leave for you. Paranoid? Perhaps.

Perhaps not – when fifth graders are involved. The Charleston Post and Courier reports:

Sixteen fifth-graders met with a police investigator Tuesday and answered questions relating to the poisoning of a Boulder Bluff Elementary School [in Goose Creek, SC] teacher who fell ill in class earlier this month, school officials said.

The four questions dealt generally with the circumstances surrounding the Nov. 16 incident, which is thought to have resulted after the teacher ingested methanol and a chemical [ethylene glycol] found in antifreeze.

That’s quite a poisonous brew. The lethal dose for either ethylene glycol or methanol is about a hundred milliliters. In other words, drinking about a quarter of a soda can of either substance could kill you.

And if you don’t die from the stuff, you will not have a pleasant day. From the MSDS sheets,

[Methanol can cause] headache, drowsiness, nausea, vomiting, blurred vision, blindness, coma, and death.

[Ehtylene glycol can cause] CNS depression, vomiting, headache, rapid respiratory and heart rate, lowered blood pressure, stupor, collapse, and unconsciousness with convulsions. Death from respiratory arrest or cardiovascular collapse may follow.

Nasty stuff.

From the article, it appears that students are possible suspects in the poisoning.

‘It’s terrifying,’ Stiles [a mother of one of the 5th graders] said. ‘If it was a child in the teacher’s class who did it, it scares me that someone who is 10 or 11 years old would know how to mix those substances and do that.’

Actually, it’s not that hard to mix those two very common chemicals together. Both mix very well with water and are colorless. Methanol has a characteristic odor, but ethylene glycol doesn’t.

Getting the teacher to ingest the mixture would be more difficult than concocting it, but it’s not beyond the realm of possibility.

That said, this particular school has been having other problems. I hope the police have a few adult suspects.

As a chemistry instructor, one of the difficulties I face when getting incoming students proficient in the laboratory is that of using units for measured quantites. Often, students just don’t have a good grasp of how various units relate to each other.

To some extent, I can’t blame my students for being confused by units. In the USA, we use a system – and I use the word “system” here loosely – of units based almost entirely of a bunch of things that just seemed like a good idea at the time.

To see what I mean, stop and take a look at the set of units we Americans use for length:

• Starting with the small, we have the inch, which is just about the width of my thumb.
• Going a little bigger, we have the foot, which is the same thing as twelve inches.
• Going bigger than that, we can use the yard, which is 3 feet or 36 inches.
• Finally, for the big distances we have the mile, which is 1760 yards, or 5280 feet, or 63360 inches.

So, 1 mile = 1760 yards = 5280 feet = 63360 inches. Or, 1 inch = 1/12 feet = 1/36 yards = 1/63360 miles Simple, right? Easy to use and remember, right?

Of course not, since these units of length don’t relate to each other in any obvious and easily-remembered way. The situation gets even worse when you move to units for other quantities. Volume units, for instance, use completely different relationships between their units than length units do. A teaspoon is 1/3 of tablespoon, 1/6 of a fluid ounce, 1/48 of a cup, etc. – very different from the relationships between the length units. No wonder students are confused about units!

The solution to this problem is pretty obvious …. use metric. The most obvious benefit of metric is that students only need to learn one set of relationships (the metric prefixes) that work for all units, rather than a set of conversions for each kind of unit. Plus, the prefixes are based on powers of ten – which means that we can do metric unit conversions very easily.

The metric prefix milli- means 1/1000 – no matter whether you are applying it to the unit of length (as in the millimeter – 1/1000^th of a meter) or a unit of volume (as in the milliliter, 1/1000^th of a liter). Now that’s an easy system to deal with.

So, how well are we doing with metric here in the USA? Each semester I give a pre-test to my incoming chemistry students, and a few of the questions are about the metric system. In a recent semester, I found that:

• Just under twenty five percent of the students I surveyed in a college-level course didn’t know what the metric prefix “kilo-” meant. A little over seventy percent of them didn’t know what the metric prefix “centi-” meant.
• Of students who were surveyed in a non-college-transfer course (usually meaning that their goal was an associate’s degree), the percentage that didn’t know what the prefix “kilo-” meant was about seventeen percent, while the percentage that didn’t know what “kilo-” meant was about sixty four percent

What does that mean? It says to me that we’re not doing a good job getting the metric system across to students before they hit college. Either that, or all the complexity of the units in the US system is making our students confused with how all unit systems work. Food for thought …

I really like this story. It’s food for thought for all those people who think that education “should be run more like a business”.

“That’s right!” she barked, “and we can never send back our blueberries. We take them big, small, rich, poor, gifted, exceptional, abused, frightened, confident, homeless, rude, and brilliant. We take them with ADHD, junior rheumatoid arthritis, and English as their second language. We take them all! Every one! And that, Mr. Vollmer, is why it’s not a business. It’s school!”

(Thanks, PZ)