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hydrophobic and hydrophilic properties of membranes (Naked Grapes)- Jen Hinerman

Author

Jen Hinerman

Principle(s) Illustrated

  1. Polarity
  2. Phospholipids 
  3. cell membranes

Standards

California Standards 1a:

Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.

Questioning Script

Prior knowledge & experience:

Students have been introduced to polarity and phospholipids

Root question:

What will happen to a grape in 7-up?

What will happen to a PEELED grape in 7-up?

Target response:

Grape will float, peeled will sink.  
 

Explanation:

The waxy cuticle of the grape's skin is hydrophobic.  This pushes the water in the soda away, allowing more carbon dioxide molecules to congregate on the surface of the skin.  Because the Carbon dioxide is less dense than the water, the bubbles give bouyant force to the grape causing it to rise up to the surface.  The peeled grape lackes the hydrophobic coating and is hydrophilic to the water of the soda.  The water of the soda coats the peeled grape and no bubble can congregate around the grape to lift it up.

  

Common Misconceptions:

students will think both will sink, or that the peeled will float as well.

Photographs and Movies


 

References

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