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Name: Melinda H.
Status: student
Age: 17
Location: N/A
Country: N/A
Date: 2000


Question:
What role do intermolecular bonds play in why water and oil don't mix?


Replies:
Dear Melinda,

Intermolecular bonds are exactly the reason why they don't mix. Water molecules have strong bonds with one another, called "hydrogen bonds." This consists of an extraordinarily strong attraction that the hydrogens of one H2O have for oxygens of nearby H2O molecules. Oil molecules also have very strong bonds with one another, but not hydrogen bonds. Oil molecules are bonded to one another by what are called "London forces," or sometimes "dispersion forces." This is a little harder to explain in simple terms, but basically the large oil molecules tend to clump together because of these forces. However, an oil molecule does not hydrogen bond with a water molecule, and an oil molecule's dispersion attraction to a water molecule is weak compared to the oil-oil attraction. So, the water stays separate from the oil, giving rise to the old chemistry saying "like dissolves like."

best regards,
prof. topper



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