Soap and Milk-Polarity (Amanda Hrezo)
Author
Amanda Hrezo
Principle(s) Illustrated
Polarity
Hydrophobic
Hydrophilic
Macromolecules
Standards
NGSS Science & engineering standards
Asking questions
Constructing explanations
NGSS Cross-cutting concept standards
Cause and Effect
Structure and Function
NGSS Disciplinary core idea standards
HS-PS1: Matter and Its Interactions
HS-LS1: Molecules to Organisms: Structure and Process
Questioning Script
Prior knowledge & experience:
Milk has nutrients
Soap cleans milk off of glasses
Root question:
What is happening when the soap is added to the milk?
Target response:
Milk is mostly water, but it also contains vitamins, minerals, proteins, and tiny droplets of fat suspended in solution. Fats and proteins are sensitive to changes in the surrounding solution (the milk). Milk fat is a non-polar molecule and that means it doesn’t dissolve in water. When soap is mixed in, however, the non-polar (hydrophobic) portion of micelles (molecular soap structures in solution) break up and collect the non-polar fat molecules.Then the polar surface of the micelle (hydrophilic) connects to a polar water molecule with the fat held inside the soap micelle. The molecules of fat bend, roll, twist, and contort in all directions as the soap molecules race around to join up with the fat molecules.(link)
Common Misconceptions:
Soap is drawn to all dirts
You should wet your hands before using soap
Milk is just milk
Applications
- Should you wet your hand before washing them with soap?
- clean up oil spills?
Materials and Resources
- Milk, Soap, Food Coloring, Pie Tin,