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

- Polarity Demo WS

- Milk, Soap, Food Coloring, Pie Tin,

Photographs and Movies

References

Color changing milk