The Chemical Educator
© 1998 Springer-Verlag New York, Inc.
Practical Organic Chemistry for 'A' level Students. Presented by D.J.Chadwick; produced by the University of Liverpool. Published by The Royal Society of Chemistry, Letchworth, England SG6 1HN. Running time 40 mins. VHS or Beta format (PAL only). Price 29 pounds.
This video examines the practical techniques of melting point determination, recrystallization, and distillation with a view to good, safe, and efficient procedures for A-level (upper-level high school) students. It is an excellent video production on all scores and highly recommended as part of an introductory course for new A-level students. In the copy for review, the label on the video listed the three parts in the wrong order, a minor niggle! A fuller label listing durations of the three parts would be helpful in setting up the video.
The video begins with a few minutes that emphasize the importance of safe working procedures and highlight eye protection and the handling of chemical spillages.
Each of the three main sections that follow lasts approximately 15 minutes and is self-contained with title and credits. It is intended that these separate parts be viewed at appropriate and relevant moments in the course, rather than all in one session.
In the first section, Determination of Melting Point, the video examines the different types of apparatus the student may meet, explaining the working of each, and how the temperature is controlled and read. For the demonstrations, a Gallenkamp apparatus is used. There is good coverage of the preparation of the sample, and of the use and sealing of sample tubes. As is characteristic of this video, there are plenty of practical details and discussion.
The structure and sequencing is extremely well thought out. Great care in procedure is demonstrated throughout. Alternative methods where appropriate are also shown. Following both the rough and then accurate melting point determination, a mixed melting point measurement for component identification is demonstrated. The coverage is thorough, including points on how the student should record results.
The second section, Crystallization, opens with an excellent coverage of the manner of selection of a solvent for recrystallization based on dipole moment of the solvent molecule (referred to simply as solvent polarity). The dual naming of solvents with both IUPAC and common names seemed a little anachronistic for schools' use. Good environmental awareness was conveyed in the well-placed mention of escaping solvent fumes and how to minimize them. The value of a video production is especially evident in this section, where the key practical points can be made, and the longer processes of waiting for cooling, warming, and drying can be suitably edited out and shortened.
In the final section, Distillation, there is a suitable emphasis on the care of assembly of the Quickfit, and the basis of adjusting the level of heating and distillate collection procedure. I wish mention had been made, and instruction given, of the use of either silicone grease or PTFE tape on the Quickfit joints to prevent binding.
Overall, this is a valuable resource for the A-level chemistry teacher, particularly those new to the profession. In what is a model of clarity, these tours of organic techniques are extremely well devised, covering all the essential practical details. As a model lesson for trainee teachers, an analysis of this video emphasizes the importance of good planning and structure to any practical work, all well exemplified here. Good video editing has enabled a sharp concentration on the most important aspects. In terms of demonstrating the techniques, the production is faultless and well pitched for A-level students.