What physical property causes a liquid free surface to minimize its area and contract_____________?
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Answer: D. surface tension
Explanation
Surface tension is the cohesive property that causes liquid surfaces to behave like stretched membranes. Cohesive forces among internal molecules pull surface molecules inward, minimizing the total exposed surface area. This minimization effect forces free liquid droplets to form spherical shapes whenever possible. Cohesion refers to the intermolecular attraction between like molecules within a liquid substance. Surface tension has units of force per unit length or energy per unit area. Molecules deep inside the liquid experience balanced forces, whereas surface molecules experience a net inward pull.
Small insects walk across water ponds because surface tension supports their weight without breaking the interface. Droplets of morning dew form nearly spherical beads on plant leaves due to surface minimization. Industrial cleaning processes often add surfactants to lower surface tension and improve wetting capabilities. Option B describes adhesion, which is the attraction between dissimilar molecules like liquid and solid walls. Option C refers to viscosity, which measures resistance to flow rather than surface area minimization. Option E describes general material elasticity rather than the specific liquid surface phenomenon.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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