yes
Yes,slightly.
No we cannot mix water with oil.
short answer, your getting water in the oil.
Oil
Oil will not mix with water.
By separating funnel, pour the mixture of mustard oil and water into the separating funnel. Mustard oil being lighter than water floats on top. The stopcock is opened and water is allowed to separate out. The principle is that immiscible liquid separates out in layers depending upon the densities.
Oil is a lipid and lipids are hydrophobic (meaning they do not like water). Oil will "clump" together because it is trying not to mix with water. This is why you need an emulsifier like mustard to coat the oil so that it will mix with the vinegar. Once the oil is coated with mustard the oil droplet becomes less hydrophobic because the mustard surrounding it is hydrophillic (meaning it likes water).
Oil does not mix with water, not even salty sea water.
yes
Oil can't mix with water.
Oil can't mix with water.