The second semester of 2009 is drawing to a close. During this semester of 2nd year lab tutoring, I've certainly been impressed with some of the undergrads' efforts, but I've also witnessed a lot of idiotic behaviour, both in lab work and in their report writing.
Asleep at the fumehood
Why would you bother turning up to labs if you're just going to fall asleep. And is there a worse place to fall asleep than with your face planted on the bench inside the fumehood? "Dude, wake up, you can't sleep there" I exclaimed, but to no avail. "Hey, you get up, you can't sleep there" I shouted this time, but he didn't respond. By then another student required my attention, but fortunately for our sleeping student here, he was awake by the time I got back to him, about to physically pick him up and get him out of the lab. Fortunately it was only a flash column being run in his hood, nothing too dangerous.
Recrystallisation or evaporation?
The students really seemed to be confused as to what recrystallisation meant. As the title suggests, they thought that by simply dissolving the crude product and evaporating it, the Law of conservation of mass would somehow not hold true for the tiny piece of the universe inside their conical flask, and the brown impurity would simply disappear.
One of these students was both arrogant and ignorant. "Tutor, how do I evaporate this solvent faster under a stream of nitrogen?"
I didn't remember this being part of the procedure, so I asked "why do you need to do this?"
Student: "I'm trying to evaporate the solvent and I need to do it faster"
Me: "But why are doing this?" (By then I realised he was trying to do a recrys, but was trying to ask him questions so that he would understand the error of his ways)
Student: "I need to evaporate this solvent but it's very slow. I just need to do this ok? Can you just tell me how to do it faster?"
Me: "But stop for a sec, why are you doing this? What is the point of dissolving something and just evaporating the solvent?"
Student: "Can you just tell me how to evaporate this faster? That's all I need to know ok?
Me: "You're trying to do a recrystallisation, so what you need to do is dissolve it in minimum amount of boiling methanol and then let it cool slowly. You DON'T want to just evaporate all the solvent."
Student (dismissively): "Are you sure? Can you just tell me how to evaporate the solvent?"
Me: "Look, you can do whatever you like, but at the end of the day, the melting point doesn't lie. If you don't do it properly, then you're only kidding yourself because when the lab technician runs your melting point it's going to be horrendous."
Student finally realises (or did he?) his mistake but walks away without a word. He does the recrystallisation as I requested.
Rouding
Each of the tutors was responsible for marking the reports of a particular experiment for the course. I was marking one where they had to find the ratio of oxygen uptake per mole of a particular transition metal. Now everyone knows the answer was 1 oxygen molecule to 2 metal ions. As one might expect, not every student obtained experimental data that corresponded to this. Here are some of the most frustrating explanations... or the funniest explanations... and if you've been marking reports for the last 5 hours it's definitely the former.
"The ratio obtained was 1.4 to 1. Since 1.4 is closest to 1.5, the ratio can be taken to be 1.5 to 1. Therefore the ratio is 2 to 1 since 1.5 should be rounded to 2."
"The ratio determined was 2.7 to 1. Since 2.7 is not quite 3 , the ratio is therefore 2 to 1"
"The amount of oxygen was 0.0018, ~0.002. The amount of {metal} is 0.0014, ~0.001. Therefore the ratio is 0.002/0.001 = 2.0" (FYI 0.0018/0.0014 is 1.3)
Referencing
How awesome is this for a reference to a melting point
Asleep at the fumehood
Why would you bother turning up to labs if you're just going to fall asleep. And is there a worse place to fall asleep than with your face planted on the bench inside the fumehood? "Dude, wake up, you can't sleep there" I exclaimed, but to no avail. "Hey, you get up, you can't sleep there" I shouted this time, but he didn't respond. By then another student required my attention, but fortunately for our sleeping student here, he was awake by the time I got back to him, about to physically pick him up and get him out of the lab. Fortunately it was only a flash column being run in his hood, nothing too dangerous.
Recrystallisation or evaporation?
The students really seemed to be confused as to what recrystallisation meant. As the title suggests, they thought that by simply dissolving the crude product and evaporating it, the Law of conservation of mass would somehow not hold true for the tiny piece of the universe inside their conical flask, and the brown impurity would simply disappear.
One of these students was both arrogant and ignorant. "Tutor, how do I evaporate this solvent faster under a stream of nitrogen?"
I didn't remember this being part of the procedure, so I asked "why do you need to do this?"
Student: "I'm trying to evaporate the solvent and I need to do it faster"
Me: "But why are doing this?" (By then I realised he was trying to do a recrys, but was trying to ask him questions so that he would understand the error of his ways)
Student: "I need to evaporate this solvent but it's very slow. I just need to do this ok? Can you just tell me how to do it faster?"
Me: "But stop for a sec, why are you doing this? What is the point of dissolving something and just evaporating the solvent?"
Student: "Can you just tell me how to evaporate this faster? That's all I need to know ok?
Me: "You're trying to do a recrystallisation, so what you need to do is dissolve it in minimum amount of boiling methanol and then let it cool slowly. You DON'T want to just evaporate all the solvent."
Student (dismissively): "Are you sure? Can you just tell me how to evaporate the solvent?"
Me: "Look, you can do whatever you like, but at the end of the day, the melting point doesn't lie. If you don't do it properly, then you're only kidding yourself because when the lab technician runs your melting point it's going to be horrendous."
Student finally realises (or did he?) his mistake but walks away without a word. He does the recrystallisation as I requested.
Rouding
Each of the tutors was responsible for marking the reports of a particular experiment for the course. I was marking one where they had to find the ratio of oxygen uptake per mole of a particular transition metal. Now everyone knows the answer was 1 oxygen molecule to 2 metal ions. As one might expect, not every student obtained experimental data that corresponded to this. Here are some of the most frustrating explanations... or the funniest explanations... and if you've been marking reports for the last 5 hours it's definitely the former.
"The ratio obtained was 1.4 to 1. Since 1.4 is closest to 1.5, the ratio can be taken to be 1.5 to 1. Therefore the ratio is 2 to 1 since 1.5 should be rounded to 2."
"The ratio determined was 2.7 to 1. Since 2.7 is not quite 3 , the ratio is therefore 2 to 1"
"The amount of oxygen was 0.0018, ~0.002. The amount of {metal} is 0.0014, ~0.001. Therefore the ratio is 0.002/0.001 = 2.0" (FYI 0.0018/0.0014 is 1.3)
Referencing
How awesome is this for a reference to a melting point
www.essay411.com/salenh2-melting-point.html
This is the 7th entry in google when you type in the search terms salenh2 melting point (as of time of writing)
I told the students specifically that wikipedia is not a valid reference. So how surely this would be ok right?
I told the students specifically that wikipedia is not a valid reference. So how surely this would be ok right?
wapedia.mobi/en/Salen_ligand
Ahhhh undergrads...
Posts
Lol @ evap student I know who that is.... same guy who cut himself when he didn't listen to me
ReplyDeleteI don't mind students who question why I tell them to do certain things. That's my job as a tutor, to teach them and questions are good for that. But arrogance (especially when combined with ignorance) is just irritating.
ReplyDeletehahahahaha! i know exactly who you are talking about! rawrrrrrrr! if he does 3001 next year, i'm not dealing with him!
ReplyDelete