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The Chemistry of Toothpaste


 

































We are enjoying reading The Toothpaste Millionaire, by Jean Merrill; Rufus and Kate prove that you are never too young to have good ideas or succeed in business. Together they develop a simple recipe for toothpaste, manufacture, market, and sell their product and make millions -all before the eighth grade!
A great activity to go with this book is making your own toothpaste! Provide your students with these ingredients:

  • calcium carbonate
  • a mixture of 3 parts baking soda to 1 part salt 
  • glycerin
  • soap (Ivory Snow)
Have them test the ingredients for:

  • their texture
  • their ability to create suds
  • taste
and have them record the results on a scale from 1-5 (1 being the least and 5 the most). We had a wide variance in the outcome of these tests, which goes to show you that different people look for different things in their toothpaste and have different tastes.

 










The last test for toothpaste ingredients is a test for cleaning ability. Stain some tiles (the kind you use in bathrooms- you can get them at a hardware store) withsome blueberry syrup and then use the different materials to test how well they cleaned the stains. We found that they all cleaned well but soap and calcium carbonate tied for first place, with baking soda and salt in second place.

Now that your students have all the test results in for texture, suds, taste and cleaning ability, they can decide how much of each ingredient to add to their own toothpaste formulas.



Your students now have to choose how much of each ingredient to add, based on the testing they have done. Each ingredient (calcium carbonate, a mixture of 3 parts baking soda to 1 part salt, glycerin and soap {Ivory Snow}) has strengths and weaknesses and they have to choose how much of each ingredient to add based on which qualities (taste, texture, sudsing ability, cleaning ability) meant the most to them. They also have a lot of flavors to choose from. We just used regular McCormick's flavorings (coconut, cinnamon, peppermint, lemon, vanilla, chocolate to name a few). No sweeteners of any kind were added.

The youngest writes down what he has put in.

The oldest is having fun mixing her formula, despite the fact that this science activity is designed for younger students.

A young student product tests.
All activities and photos are from 5/2008

The results we had were that none of them were ready to turn in the store bought toothpaste for their own creations, but they had a better understanding about what factors go into making a good toothpaste, or perhaps, more importantly, the skills used by a scientist.


Related Posts:

Source:
  • GEMS Guide Secret Formulas    Grades 1–3 
    Students eagerly investigate the properties of substances as they make their own personal brands of paste, toothpaste, cola, and ice cream. The activities have been designed to convey key science/mathematics skills and concepts, provide motivating real-life experiences with chemistry, and build comprehension of cause and effect, central to later understanding of controlled experimentation. Secret Formulas speaks to the need expressed by many primary school teachers for more high-quality physical science activities.

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