answersLogoWhite

0


Best Answer

because most salad dresings are made up of vinegar and oil and since vinegar is water based it dose not mix with oil.Water molecules are dipolar, so they have one end that is partially positively charged (the hydrogens) and one end that is partially negatively charged (the oxygen). When you get a bunch of water molecules together they form a transient network of hydrogen-bonds, short-lived interactions between the oxygen of one water molecule and the hydrogen of a neighboring molecule. These hydrogen bonds explain water's unusually high boiling point, its decrease in density upon freezing, and its unusually high surface tension.

Oil is made of long hydrocarbons, which are nonpolar. Nonpolar molecules don't really have much incentive to stick to each other. They do experience very weak attractions called van der Waals forces when they are close to each other, but these are common to all molecules.

When you try to mix water and oil together the water "wants" to satisfy its hydrogen bonds. This is best done by sticking together with other water molecules. The hydrocarbons don't really "want" water there or not, but are happy to exclude water if it "wants" to go somewhere else. The result is a biphasic mixture. Oil ends up being the top layer because it is less dense than water, but there are also nonpolar liquids that are more dense than water, and in that case the aqueous phase would be the top layer. Sometimes the two densities are close enough that which one ends up being on the top is a matter of what else is dissolved in each solvent (seen sometimes in aqueous extractions with chloroform or dichloromethane--always check to make sure you've got the right phase before dumping the rest down the drain!)

User Avatar

Wiki User

15y ago
This answer is:
User Avatar
More answers
User Avatar

Wiki User

15y ago

less dense stuff goes to the top. in this case the oil. then the other stuff goes to the bottom. this is because the two ingreadients don't mix. but when they do, it's only for a short time The answer above isn't quite right. The two mixtures are of different polarities. Oils and lipids are nonpolar while watery substances such as vinegar (mostly water) are polar. That's where the density part comes in. Because of their polarity, they cannot mix which means the less dense substance is on top and the dense substance is on the bottom respectively. Do NOT think that just because the two different substances have different densities, they won't mix. If they have the same polarity, then they will mix REGARDLESS of density.

This answer is:
User Avatar

User Avatar

Wiki User

12y ago

Because the density level of the ingredients have a very large difference. Even though the density of subbstance is a characteristic property of matter (no other substance in the world can have its density), the ingredients wouldn't separate because their density levels aren't that far appart; they are close.

hope that helps!

This answer is:
User Avatar

User Avatar

Wiki User

10y ago

Water is a polar molecular, but oil is a non-polar molecule. Only combinations of polar-polar or nonpolar-nonpolar can mix into a solution. Thus they remain separated.

This answer is:
User Avatar

User Avatar

Wiki User

13y ago

It's all about specific gravity, a liquid's equivalent to mass. Liquids with higher specific gravity will sink below liquids with lower specific gravity.

This answer is:
User Avatar

Add your answer:

Earn +20 pts
Q: Explain why an oil and vinegar salad dressing seperates?
Write your answer...
Submit
Still have questions?
magnify glass
imp