My Notes
Categories
This is a short presentation that outlines the major chemical reactions of soapmaking. Included are instructions for making two soaps, one from canola oil, the other from coconut oil. These two soaps have very different hardnesses, which can be explained by examining the structures of the oils. If you have never made soap before, it isn't that difficult, but it does use concentrated NaOH so is very caustic before the reaction is done. The linked websited have good instructions for soapmaking as well.
The powerpoint is annotated with notes and suggestions. There is a student handout too.
Questions are provided that students could do as homework. The answers are included as faculty only files.
| Attachment | Size |
|---|---|
| powerpoint for a lecture/demonstration | 4.65 MB |
| student handout or online resource | 407.43 KB |
1. Identify the major functional groups found in soap and used in soapmaking
2. Explain how soap works at the molecular level
3. Draw balanced chemical reactions for the soapmaking process
4. Calculate various metrics for soap and relate them to the soap’s properties
5. Compare different ways of calculating the molecular weight of soap and polymers
This was used as the first day in a two-day module in first-year chemistry. The second day used in-class small group work to calculate some of the metrics in soap and further examine the chemistry of soap. For 2016, I am adding a third day to finish up calculations and have groups report back on their findings.
Evaluation
There was no evaluation on the lecture/demo. The exercises were graded according to the provided key. The answer key here is the same as the first answer key in the linked in-class activity.
Students were generally able to do the calculations without too much trouble, once they realized it was just a limiting reagent calculation. I got several actual "cartoons" for the 2nd part, and I awarded bonus points for students who were creative and drew me a 1 or 4 panel comic strip.
It is MUCH quicker to reach trace for canola oil (5 min) than for coconut oil (> 15-20 min). When the coconut reaches the consistency of about glue (5-10 min), you can pour it and it will set up nicely. The canola soap will reach a pudding-like consistency and you can either pour it or spoon it into the container. For an in-class demo, making canola will work better.
for class demo, its easiest to use only a single color, but if you want to extend this to home soap making, you can color only half and have a 2 color soap. Pour it in alternating lines and then drag between the layers with a dowel, chopstick, or plastic knife.