As we discussed in Lesson 2, water really only dissolves polar or charged molecules.
Scientist You Should Know
Dr. Herbert S. Smitherman (1937-2010) invented Crest toothpaste, among other products during his career at Proctor and Gamble. These products also include a sulfonated detergent. Organic chemistry is a big part of cleaning because of how oily stains don’t dissolve in water.
https://www.theroot.com/did-a-black-man-invent-crest-toothpaste-1790877449
https://blackthen.com/dr-smitherman-herbert-first-black-doctorate-level-physicist-chemist-proctor-gamble/
https://blackamericaweb.com/2015/10/21/little-known-black-history-fact-dr-herbert-smitherman/
Introducing the Topic
Soap connects water to nonpolar molecules like oils, many soil particles, and odorous aromatic compounds. That’s because it has a polar “head” and one or more nonpolar “tail(s).” (More on how it relates to cell membranes in future lessons)
Here’s the engineer’s version:
Experiencing the science
It’s an oldie, but a goodie: Bubble blowing. Use a journal to record observations. Measure, try different tools, contemplate the variables. Describe the system. What can be changed? What can be measured?
Responding/analyzing
Multisensory
Run a bubble bath. What works best? What doesn’t work? Now get in. Make a bubble beard. Make a bubble sculpture. Hold an armload of bubbles. Are they heavy? Can you feel them at all? Close your eyes.
Creative
Soap making is an ancient artisan technique. Look up some recipes for making soap. Some of them will involve the saponification itself. Others, like this one, will start with a soap already made:
https://tinkercast.com/resource/craft-play-dough-soap/
Here’s a cool story about a woman who made a big impact on haircare history:
https://tinkercast.com/podcasts/wewow-day-2-lets-meet-entrepreneur-madam-cj-walker/
Verbal
Make a timeline of the history of soap. Make sure you remember to look out for women in the story, especially women of color. These people often get erased when history gets told, but they were definitely there. Especially when it came to domestic tasks like cleaning.
Analytical
There is a super popular introduction to experimental design lab out there called Bubble-ology. It got introduced at the IB sciences conference I attended, and it pops up a lot in “inquiry lab” instruction. The key is to blow the bubble onto a surface so that you get a nice round impression you can measure.
Like at time stamp 6:15 of this video (I dislike that the guy says “prove.” Scientists can “disprove” or “support” or “illustrate,” but we don’t prove anything.)
A lot of people compare brands of dish soap. This can make a bar graph. I love a scatter plot and a regression, myself, so I like to recommend changing soap concentration as the independent variable. You can then measure the diameter of the biggest bubble possible. Replicate each concentration.