I have used your videos for help when writing almost every single one of my lab reports for organic chem 1. Thank you so much for taking the time to make the videos and including such helpful diagrams. Your way of explaining is so effective - it really helps with understanding the theory behind all these experiments.
These videos are very great for actually understanding the science behind each experiment. My organic lab doesn't really teach conceptually anything, they just give you a procedure and you follow it. Thanks!
Omg thank you so much for this video. It helped in a crunch. Having to write our first lab notebook and I was so co fused as to why melting point depresses. Really effective as I am a visual learner, and you instruction was simple, concise and to the point. Thank you.
Thanks, Professor Davis, I haven't watched the whole video yet, I am sure this video is going to be useful for me already. Please keep helping students by making these kinds of videos! You saved a lot of my time
so glad you appreciated it! I am hoping to produce a few more videos later this summer. Don't forget to subscribe to get notifications when new videos go up!
loved this video. you hinted that you would go into more detail of the "range of melting temps" (2:40) for impure mixtures. i would find that information interesting. I looked around for a bit but couldn't find anything like that. did you ever make a video on that?
so if a compound is pure and an impurity with a much higher melting point is added, will the melting point of the new solvent be somewhere in the middle?
+Orgo Keigxan Theoretically, not necessarily. In a very simple, very well-behaved system like the one you describe, the melting point of the pure sample would still be depressed by the addition of a SLIGHT amount of the high-melting impurity. But here is the catch, the eutectic composition of such a mixture is likely to be very close to the original pure compound (maybe 95%, for example), so depression of its melting point is only observed when a very small amount of the second compound is added. Once you cross the eutectic point, melting points will begin to increase again and our assumptions about depression go out the window! This is exactly why only a small amount of standard is added during mixed melting point tests. If you cross the eutectic your results will be ambiguous. If you are performing a mixed melting point analysis, then obviously you aren't sure what you have or what its phase diagram looks like. So, to be sure that melting point depression happens for every additive except for the original compound, we only add a pinch of standard just in case we are wrong!
