To stop doing labs is to stop teaching science.

Quoted for truth. Science is about research and it is about *experiment*. If schools are eliminating lab time, is it any wonder that so many whackos on the Internet today believe that reading stuff from Google counts as research? When they went to school, it probably *did* count. There is a very real sentiment that any knowledge that is worth knowing must be out there on the Internet, waiting for just the right Google search to reveal it. This is a dangerous attitude, and a very sad one.

When I was in high school, I had some awesome teachers for chemistry, physics, and biology. We got lab time, too. It was lovely. But I know there wasn’t anyone in charge of the labs. Each teacher was responsible for their own lab, in addition to their teaching duties. The biggest safety problem we ever had was more of a facilities issue — a gas line leading to the chem labs ruptured, triggering an evacuation. (In January. THAT was fun. After a while, as they realized the problem could not be resolved quickly and none of us had outerwear, we were relocated to the cafeteria, which was at the opposite end of the building from the labs.)

My first thought when I saw this story on the news was that the teacher probably didn’t do a trial run of the experiment on his own. Also, I seem to recall hearing that there were other flammables on the bench which contributed to the seriousness of the problem. The latter is a lab safety issue, but the former makes me think of a professor I had in freshman chem at college. He had a tendency to do experiments in class which he’d never attempted before. Sometimes they went badly. He came up with a great idea to let us all see liquid carbon dioxide. He appropriated a disposable eyedropper from the bio department. He opened the tip up a little so he could squeeze some dry ice inside. Then he clamped it shut with a pair of pliers and held it over a overhead projector. This projected its silhouette onto the wall, as the heat from the bulb rapidly warmed the CO2. And it worked! We actually could see *boiling* CO2 inside the eyedropper — for about five seconds. Then he lost his grip on the pliers, and the eyedropper shot across the room like a rocket, bouncing off of several walls before coming to a stop. Fortunately, no one was hurt, but that could’ve put out an eye. This was in a classroom, not a lab, so nobody was wearing any sort of eye protection.

BTW, I have to second the comment about wearing eye protection even for doing stupid banal things. You don’t know what some other idiot is doing. My daughter’s eye doctor has a video running on continuous loop in his waiting room. It’s a good educational bit, explaining terms and what sorts of products are available for various things. No brand names get mentioned; it is purely educational. A fairly long segment is devoted to occupational injuries. It cites a statistic (don’t remember the exact number nor where they got it — I’ll have to pay attention next time I’m there) saying how many eye injuries are the result of *someone else’s work*. Maybe you’re not machining right now, but if the guy 20 feet away is, you could still get shrapnel in your cornea. I would guess this number is as high as it is mostly because people tend to base their eyewear needs on what they themselves are doing.

–bks

When I taught Horticulture in a high school, I had to look after landscaping equipment and supplies, manage 2 greenhouses (not too small either) and a small nursery, handle FFA and… oh yeah, teach. I had been promised a student helper, but that never materialized. It certainly made things hard. I hope at least to have other science teachers to work with when I teach again.

http://www.startribune.com/local/west/134841058.html

It was lighting the fumes inside a jug of methanol. The problem with using methanol is that at room temperature, the vapor pressure of pure methanol puts pretty much exactly the stoichiometric fuel/air ratio inside the jug. Methanol jugs are usually not made to withstand any kind of handling or pressure, so it burst.

The way to do this is with something safer, like vodka. Straight grain alcohol (190 proof) has a lower vapor pressure than methanol, but ethanol has a higher molecular weight so the stoichiometric fuel/air ration is lower too. It turns out that at room temperature the vapor pressure of pure ethanol is also pretty much exactly the stoichiometric fuel/air ratio.

You don’t want a stoichiometric fuel/air ratio, you want something that will burn, but that won’t burn so fast that it breaks the bottle. You need to use a more dilute solution of alcohol (80 proof works pretty well), and you also want to make sure that you don’t have a lot of excess fuel in the bottle (i.e. drink most of it first). That is harder to do with methanol because you can’t drink it more than once. The water depresses the vapor pressure of the alcohol so there is less fuel in the air.

Also, the bottles that vodka come in are stronger than the bottles that methanol comes in. They are also smaller (1.75 liter vs 3.8 liter) and have a handle which acts as reinforcing. I have never had a liquor bottle explode on me. Also, methanol bottles tend to be brown glass which really detracts from the effect. You want a sub-stoichiometric fuel/air mixture so that the flame front moves slowly.

Also, take out the speed pourer or the restriction will greatly accelerate the combustion rate (then the bottle might break).

We burned magnesium and used a silver solution (the stain stayed on my finger for most of a year). We also watched a small clod of sodium zip around a bucket of water. We also did the hydrogen courage test, after producing our own H2 with HCl and Mg. And this was in 1998/99. Of course this was in Alberta.