Why is Oil not soluble in water?

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Why is Oil not soluble in water?

Notice that when there is an oil spill from a tanker, it shows up in the surface of the ocean or when you put olive oil in your salad, it separates itself from the dressing or when it rains, small puddles of oil are seen in the road making it slippery. No matter how much you shake it or combine the two, water and oil won’t just mix.

There are two basic reasons why oil is not soluble in water: (1) oil is hydrophobic or water fearing”, (2) oil is non-polar while water is polar.

Hydrophobic or water fearing”. Most oil is not soluble in water because they are water fearing” or hydrophobic in nature and this goes for all lipids.

Oil is composed of a long chain of hydrocarbon molecules usually 8 Carbon atoms (substances made from entirely hydrogen and carbon) which do not carry an electric charge. This molecules are hydrophobic, they are immiscible in water which means they don’t like’ making contact with water.

Due to the lack of charge, no attraction between the water molecules and the long carbon chains can be formed because oil molecules are more attracted to each other than to water molecules and vice versa thus they cannot mix because they can’t create any bond with each other.

Difference in Polarity. Basically, oil is non-polar while water is polar. This difference greatly affects the solubility of oil in water. Whether a solute dissolves or not, it follows a certain rule like dissolves like”. Unless the solute and solvent are both polar or both nonpolar; then the solute will not dissolve.

A polar substance has two kinds of poles’ like in a magnet. When another substance is polar, the poles of this two substance attract each other resulting in a mixture of both substances.

Oil on the other hand is non-polar. It contains no poles that can attract the water molecules which is why is cannot dissolve in water. Rather it floats like ice due to its smaller density.

In conclusion, oil is not soluble in water because it is hydrophobic in nature. Another reason is because is because of the difference in polarity of oil and water.

Author: joanna

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