Water has a relatively high surface tension compared to oil. When oil is placed on water, the water molecules are strongly attracted to each other (high cohesive forces), causing the water surface to try to contract. The adhesive forces between oil and water molecules are greater than the cohesive forces within the oil, allowing the oil to be pulled outward and spread thinly across the water surface, driven by the attempt of the water surface to minimize its area. Oil spreads because its surface tension is lower than water's.
Oil spreads over the surface of water because :
Asked in UPPCS Prelims 1994 · Topic: Physical Properties of Materials (Viscosity and Surface Tension)
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Answer: D. Oil has less surface tension than water
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