Day: July 8, 2013

Monday, 8 July 2013

07:41 – Costco run and dinner with Mary and Paul yesterday. I asked Paul about the lab skills of incoming freshmen chemistry students, and he said that with very few exceptions they pretty much didn’t have any. Many of them are very bright kids. They easily grasp the theory, but they’ve never had any hands-on lab work to speak of so they’re clueless about how to do even simple procedures. Paul mentioned one first lab class where they were doing simple procedures that he said either of us would have finished in half an hour. Hours later, the kids were still struggling and nowhere near finished. He finally just told them to go home. Paul particularly remembered one boy, who was extremely bright but had no practical experience. Paul was horrified to find the boy weighing out a chemical by transferring it directly to the pan of the scale rather than using a weigh paper or boat. He asked the boy how he planned to get the chemical off the scale. Presumably by inverting the scale to dump the chemical.

When I was doing high-school and undergrad chemistry, we spent much, much more time in lab than kids do nowadays. That’s probably a result of both costs and concerns about safety. Many public schools nowadays have limited or no lab facilities and the cost of materials is a big hurdle for most of them. A year-long highschool chemistry course in many public schools provides little or no actual hands-on lab work. Students watch demonstrations. If they’re lucky, it’s the teacher doing an actual demonstration, but increasingly it’s demonstration videos. As I’ve said, that’s kind of like trying to learn to drive a car by watching a video of someone else doing it.

Homeschoolers generally do better, but still devote too little time to hands-on lab work. A typical homeschool chemistry course may devote one day every two weeks to lab work. When one of them asks me, I recommend that they average spending 40% to 50% of their time on lab work, call it two sessions or more a week. And I also recommend that they reverse the usual prioritization. Instead of making textbook lecture first priority and filling in any remaining time with lab work, devote as much time as necessary to getting through all the labs and then use whatever time is left over for lectures. Their kids will be better prepared for college science. They’ll hit the ground running.

Yesterday and overnight, we had almost 3 inches (7.5 cm) of rain. Another month’s worth of rain in one day. Things are getting a bit soggy around here.

11:25 – I’m filling some containers with chemicals that are hazardous or obnoxious, or both. These are ones that I won’t let Barbara deal with. I just finished a batch of thirty 25 g bottles of sodium dithionite. It’s hazardous because it’s a spontaneously flammable solid, and it’s obnoxious because it reeks to high heaven. The odor isn’t intense or immediately obvious, but it’s persistent and it smells like something died.

Next up is filling a bunch of polypropylene RIA vials with 500 mg each of crystal iodine. It’s nasty stuff, a strong corrosive. It’s not as bad as bromine, which in turn isn’t as bad as fluorine, but it’s still pretty bad. Not something I want to get on my skin, so I’ll wear nitrile gloves. Which should tell you something, because I usually don’t wear gloves to handle the big three concentrated mineral acids–hydrochloric, sulfuric, and nitric. But iodine is corrosive enough that I won’t take chances with it. Put it this way: one time I was weighing out iodine to make up iodine-iodide solution and made the mistake of using a chrome-plated steel spatula. As I transferred the iodine crystals from the spatula to the weigh boat, I noticed that the spatula was no longer chrome-plated where the iodine had contacted it.

After that, I’ll fill a bunch of polypropylene RIA vials with 500 mg each of ninhydrin, which isn’t particularly hazardous but is another of the chemicals I won’t let Barbara handle. Ninhydrin is used to visualize latent fingerprints. It reacts with skin oils to form an intense purple dye. Which means it also stains skin an intense purple color, which stains aren’t easily delible.

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