WEBVTT 00:00:00.000 --> 00:00:02.840 align:middle line:84% PHIL: The prize for the biggest crystal is a lunch 00:00:02.840 --> 00:00:07.900 align:middle line:84% with John and the TAs at Legal Seafood, which I'm personally 00:00:07.900 --> 00:00:10.016 align:middle line:90% very excited about. 00:00:10.016 --> 00:00:40.520 align:middle line:90% [MUSIC PLAYING] 00:00:40.520 --> 00:00:43.490 align:middle line:84% NARRATOR: Today the students are going to learn a totally 00:00:43.490 --> 00:00:46.165 align:middle line:84% different technique, recrystallization. 00:00:46.165 --> 00:00:49.120 align:middle line:84% PHIL: Pesticides, pharmaceuticals, food 00:00:49.120 --> 00:00:52.870 align:middle line:84% colorings, and products where they have to produce tons per 00:00:52.870 --> 00:00:56.510 align:middle line:84% year, recrystallization is the key method. 00:00:56.510 --> 00:00:58.550 align:middle line:84% Yesterday you were working with about 100 00:00:58.550 --> 00:00:59.890 align:middle line:90% megs of each compound. 00:00:59.890 --> 00:01:01.975 align:middle line:84% Today, you're going to be working with 2 grams. 00:01:01.975 --> 00:01:04.080 align:middle line:84% NARRATOR: But there's more on the line than just getting 00:01:04.080 --> 00:01:05.800 align:middle line:90% those 2 grams back. 00:01:05.800 --> 00:01:08.750 align:middle line:84% This is practice for next week's crystal competition. 00:01:08.750 --> 00:01:11.010 align:middle line:84% If the students do well, they'll have a better shot at 00:01:11.010 --> 00:01:14.200 align:middle line:84% winning a free lunch with the teaching staff. 00:01:14.200 --> 00:01:16.570 align:middle line:84% The first step in a recrystallization is to choose 00:01:16.570 --> 00:01:18.020 align:middle line:90% the right solvent. 00:01:18.020 --> 00:01:20.520 align:middle line:84% The students need a liquid that will not dissolve the 00:01:20.520 --> 00:01:23.520 align:middle line:84% target molecule when it's cold, but will dissolve it 00:01:23.520 --> 00:01:24.510 align:middle line:90% when it's hot. 00:01:24.510 --> 00:01:27.360 align:middle line:84% The students then dissolve the sample in hot solvent and 00:01:27.360 --> 00:01:29.570 align:middle line:84% filter out any solid impurities. 00:01:29.570 --> 00:01:32.220 align:middle line:84% Then they cool it down in an ice bath. 00:01:32.220 --> 00:01:35.280 align:middle line:84% The target molecule should crystallized out of solution 00:01:35.280 --> 00:01:36.880 align:middle line:90% forming a pure solid. 00:01:36.880 --> 00:01:39.120 align:middle line:84% The impurities should stay in the liquid. 00:01:39.120 --> 00:01:39.560 align:middle line:90% ANTHONY: Fresh. 00:01:39.560 --> 00:01:40.000 align:middle line:90% IKE: Yep. 00:01:40.000 --> 00:01:41.880 align:middle line:90% That's how we want it. 00:01:41.880 --> 00:01:42.690 align:middle line:90% Crystal clear. 00:01:42.690 --> 00:01:45.520 align:middle line:84% NARRATOR: Ike, Ethan, and Anthony are having 00:01:45.520 --> 00:01:47.270 align:middle line:90% no problems at all. 00:01:47.270 --> 00:01:49.840 align:middle line:84% ETHAN: Ain't nothing too hard for an MIT chemist. 00:01:49.840 --> 00:01:53.675 align:middle line:84% NARRATOR: Hansol, Jason, and Fred on the other hand-- 00:01:53.675 --> 00:01:56.815 align:middle line:84% HANSOL: I made like two, actually three mistakes today. 00:01:56.815 --> 00:01:58.870 align:middle line:84% JASON: I've made so many stupid mistakes today. 00:01:58.870 --> 00:02:01.090 align:middle line:84% HANSOL: Yeah, I didn't realize it would heat that fast. 00:02:01.090 --> 00:02:04.250 align:middle line:84% FRED: Um, it exploded all over the side of my flask. 00:02:04.250 --> 00:02:06.170 align:middle line:84% HANSOL: And then it exploded, so then I had to start over. 00:02:06.170 --> 00:02:08.900 align:middle line:84% PAUL: It started sputtering out and actually 00:02:08.900 --> 00:02:09.530 align:middle line:90% it was kind of scary. 00:02:09.530 --> 00:02:12.190 align:middle line:84% Some of it almost like hit me in the face. 00:02:12.190 --> 00:02:13.530 align:middle line:84% JASON: I've broken a test tube. 00:02:13.530 --> 00:02:15.975 align:middle line:84% HANSOL: And then I put it through a small funnel which 00:02:15.975 --> 00:02:16.590 align:middle line:90% was a total mistake. 00:02:16.590 --> 00:02:20.510 align:middle line:84% JASON: I put too much solvent losing some product. 00:02:20.510 --> 00:02:22.595 align:middle line:84% HANSOL: The funnel, I just dropped it. 00:02:22.595 --> 00:02:22.860 align:middle line:90% So-- 00:02:22.860 --> 00:02:26.340 align:middle line:84% JASON: The yield on this is almost nothing. 00:02:26.340 --> 00:02:29.470 align:middle line:84% NARRATOR: After filtering, washing and drying, everyone 00:02:29.470 --> 00:02:32.520 align:middle line:84% eventually makes it to the final step, weighing the 00:02:32.520 --> 00:02:34.770 align:middle line:90% purified crystals. 00:02:34.770 --> 00:02:37.730 align:middle line:90% Getting 90% yield is the goal. 00:02:37.730 --> 00:02:41.180 align:middle line:84% That would be 1.8 grams of the original crystal. 00:02:41.180 --> 00:02:42.570 align:middle line:84% LEALIA: So far my yield says 1.9 grams. 00:02:42.570 --> 00:02:45.270 align:middle line:84% So I don't know if that's right because there is only 00:02:45.270 --> 00:02:46.475 align:middle line:90% supposed to be two grams. 00:02:46.475 --> 00:02:48.640 align:middle line:84% JULIE: That's probably not going to be that good because 00:02:48.640 --> 00:02:50.080 align:middle line:90% that all I have. 00:02:50.080 --> 00:02:53.050 align:middle line:84% There were some problems with filtering and then also 00:02:53.050 --> 00:02:55.630 align:middle line:84% noticed trying to put the stuff in the beginning, I 00:02:55.630 --> 00:02:59.100 align:middle line:90% spilled it everywhere. 00:02:59.100 --> 00:03:01.130 align:middle line:90% YI-SHIUAN: Is it really pure? 00:03:01.130 --> 00:03:03.810 align:middle line:90% JULIE: 7%. 00:03:03.810 --> 00:03:05.160 align:middle line:90% LEALIA: 101% yield. 00:03:05.160 --> 00:03:06.410 align:middle line:90% JULIE: Good job. 00:03:06.410 --> 00:03:08.920 align:middle line:90% 00:03:08.920 --> 00:03:10.170 align:middle line:90% JASON: 3%. 00:03:10.170 --> 00:03:11.980 align:middle line:90% 00:03:11.980 --> 00:03:14.750 align:middle line:90% So besides 3% yield, my melting 00:03:14.750 --> 00:03:16.000 align:middle line:90% point's almost perfect. 00:03:16.000 --> 00:03:18.334 align:middle line:90% 00:03:18.334 --> 00:03:20.990 align:middle line:84% NARRATOR: For some today, a good start. 00:03:20.990 --> 00:03:22.540 align:middle line:90% For others-- 00:03:22.540 --> 00:03:24.560 align:middle line:90% JASON: 3% yield. 00:03:24.560 --> 00:03:25.220 align:middle line:90% You needed 90%. 00:03:25.220 --> 00:03:26.955 align:middle line:90% I only got 3%. 00:03:26.955 --> 00:03:30.530 align:middle line:84% NARRATOR: Not looking so hot for next week. 00:03:30.530 --> 00:03:32.490 align:middle line:84% Tune in, and see how it all unfolds. 00:03:32.490 --> 00:03:37.780 align:middle line:90% 00:03:37.780 --> 00:03:40.700 align:middle line:84% PHIL: Just make observations, write down what could have 00:03:40.700 --> 00:03:43.072 align:middle line:84% went wrong, what you could do differently next time. 00:03:43.072 --> 00:03:44.085 align:middle line:90% JASON: Not spill. 00:03:44.085 --> 00:03:50.290 align:middle line:84% Sleep more beforehand so I don't make mistakes. 00:03:50.290 --> 00:03:50.890 align:middle line:90% Not spill. 00:03:50.890 --> 00:03:53.290 align:middle line:90% PHIL: Take your vitamins. 00:03:53.290 --> 00:03:54.790 align:middle line:90% JASON: Not be an idiot. 00:03:54.790 --> 00:03:56.590 align:middle line:90% I don't know. 00:03:56.590 --> 00:04:02.923 align:middle line:90% [MUSIC PLAYING]