Oil spreads over the surface of water, whereas, water does not spread over the surface of oil. Why?

Q.     Oil spreads over the surface of water, whereas, water does not spread over the surface of oil. Why?

Ans.     The surface tension of the water is more than of oil. Therefore, when oil is poured over water, the greater value of surface tension of water pulls the oil in all direction and as such it spreads on the water. On the other hand, when water is poured over oil, it does not spread over it because the surface tension of oil being less than that of water, it is not able to pull water over it.    

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