Question

Why is oil preferred for frying and not water?

Answer 1

We prefer oil frying and not water because the boiling point of oil is much higher than the boiling point of water. Average boiling point of oil is 200 degree Celsius and the boiling point of water is 100 degree Celsius. So when we put any vegetation or water into the boiled oil, the oil evaporates the water by its high temperature. Hence, this is the key point of frying the oil and not the water.

Complete answer:
When oil and water is at normal temperature then oil floats on the water due to their density. Where the density of oil is 921 kg per cubic meter and density of water is 1000 kg per cubic meter. Density is the ratio of mass of body and volume of that body.
Water ($H_2O$) is a stubby molecule with a slightly positive charge on the hydrogen (H) and slightly negative charge on the Oxygen. The negative poles on each water molecule are attracted to the positive moles on other molecules and as a result, they knit tightly together with hydrogen bonds. oil floats on water because of its low density, by this occurrence super tight hydrogen bonds are formed between water molecules and hold them closer together, the bonds between the fatty acid molecules that primarily make oil.

Note:
As for oil, it is a non-polar chemical. Since the atoms in the fatty acids in oil share their electrons nicely, they have no charge or at least not enough to make the whole molecular polar. Given their lack of positive and negative charge, they are not attracted to polar molecules, like water.