As we know that everything around us is made up of tiny particles known as molecules. The way two substances interact depends on the molecules that make up the substances. Therefore the molecular structure of water and oil determines the way that they interact with each other. Also, oil and water do not repel each other. We have seen lot many times that oil and water do not mix together or haven’t you noticed that when we wash oily hands in just water still oil remains in our hand. Why is it so? Let us find out from this article that why oil and water doesn’t mix together.
What is oil?
Oil is a hydrocarbon in liquid form which is greasy to touch and is formed by natural resources or the breakdown of fats. It is combustible that burns. It is used as a fuel i.e. petrol is made from oil only; in houses oil is used for cooking food and it act as lubricant also.
Why oil and water doesn’t mix together?

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Molecules of oil are bigger than that of water and therefore do not mix easily. On the other hand molecules of water are polar, i.e. it is positively charged at one end and negatively charged at the other whereas oil molecules do not have; as a consequence they tend to stay away from water molecules. Therefore, oil and water don’t mix together. Water molecules are made up of two hydrogen atoms and one oxygen atom each. Since only opposites attract, the water molecules stick to each other. Polar molecules only dissolve in polar solvents. Similarly, non-polar molecules only dissolve in non-polar solvents. Oil is made up of non-polar molecules having negative charges, or electrons, surrounding the molecule. And so oil molecule stick to each other. Even if you stir water and oil together, they will eventually separate in to two different layers.
But they can be forced to mix together by adding an emulsifier. This emulsion will create a stable mixture of water with droplets of oil spread through it or oil with droplets of water spread through it, does not settle out.
Why oil floats in water?

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When we put some oil in water instead of mixing it together, it starts floating on top of the water. Because it is less dense i.e. as spoonful of oil weighs less than a spoonful of water. When we sprinkle salt in water, now what will happen? Salt is denser than water, it weighs the oil down and makes it to sink. Once the salt dissolves in water, the oil floats back up to the top of the water.
From the article it is clear that why oil does not mix with water and floats on it.

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