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Can someone please help me with this question regarding hydrophobic molecules in water? CHEM/BIO- IM STUCK!!!


Which is the most accurate statement of the phenomenon underlying 'hydrophobicity', the clustering of oily molecules in the presence of water?
Select one:
a. it's all about size--oil molecules are long, so interact more with other long oil molecules
b. oil molecules interact tightly, causing clusters from which water is excluded
c. water molecules lose opportunities to form bonds with each other when 'interrupted' by oily/hydrophobic ones
d. water molecules 'flee' oil molecules, leaving the oils together
e. like attracts like--water molecules bond to other waters, and oils to other oils.

I believe it is either c. or d., but I am not sure which. In fact, I am leaning more towards d, since hydrophobic molecules do not really have positive interactions with each other and water molecules just want to avoid them since they have nothing to offer in terms of positive/negative partial charges.
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4 Answers

Hi Angelica!
 
I think you are narrowing it down very well.  From all that I have learned about the hydrophobic effect and its use in soaps and detergents, I think the answer c is the closest, since it deals with how water is freer to form hydrogen bonds away from the nonpolar molecules.  So they more readily form bonds with each other away from the hydrophobic material.  So, if I were choosing, I would choose c.
Hydrophobic is a term that applies to  lipid molecules, especially saturated fatty acids where all hydrogen bonds are occupied and cannot bond with oxygen molecules to form water. 
 
So if someone is trying to dissolve oil or liquefied butter in water then either will  form separate layers and the substances would be known as hydrophobic, the substances that repel water and form two layers when added to water. 
 
The definition of hydrophobicity would be the property of lipid molecules or fats/fatty acids to remain separate  with water molecules in a mixture, in other words it is their inability  form a homogeneous solution due to unavailability of hydrogen molecules in their structure. 
 
 
Hydro means water.  Phobia means fear.  The oil is 'afraid' of the water so it groups together to try to avoid it and stick by the oil.  d.
Its e. Both types of molecules form their own bonds or interactions with other molecules with similar functional groups.
Hydrogen bonds for water and hydrophobic for non polar molecules.
 
This is why phospholipids are an imporyant component of cell membranes. Their charged, polar heads interact with water in the cytosol and the environment but their nonpolar tails pack clisely together