Have you ever wondered why do oil and water not mix? You can try this experiment, it is kind of fun actually. All you need is some water and oil, and try mixing them together. Well, there is a scientific explanation behind this not-together-ship between these two. Not really scientific, but it related to chemical thingy so here is why.
Oil and water do not mix because the molecules or tiny particles of them are so different from each other. The molecules in oil are much bigger and contain many more atoms compared to water. So, 2 different liquids are able to mix with each other because they have similar types of molecules. For example, milk and water. But in case of oil and water, their molecules prefer to stay apart instead of mixing.
If you try the experiment, you will see that there are circle patches of oil floating on top of the water. That is because of another characteristic of molecules that produce ‘surface tension’. This tension is a cohesive force that is caused by the attraction of the molecules to each other. They cling so tightly that they produce a surface layer which acts like an elastic skin.
Short and precise, I hope that this help clear your doubt in case you are curious about this.