nserv3 - Surface Tension Some consequences of surface...

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Surface Tension Some consequences of surface tension.
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At the interface between a liquid and a gas, or between immiscible liquids, cohesive forces acting on the liquid molecules are unbalanced. The apparent physical consequence of this unbalanced force is the creation of a surface tension/hypothetical skin . A tensile force due to molecular attraction may be considered to be acting in the plane of the surface along any line. For a given liquid, the surface tension depends on the temperature as well as the other fluid in contact .
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Due to surface tension, a steel needle may float on a liquid surface. Similarly, a small droplet of mercury will form into a sphere due to large cohesive forces holding the molecules together.
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The origin of surface tension Figure shows a liquid in contact with its vapor. There is a gradual change of properties in the interface region between the phases, which is about 1nm thick. Molecules are attracted to each other: those at the surface of a liquid have no molecules above them, resulting in a net attractive force inwards. We just noted that: At the interface between a liquid and a gas, or between immiscible liquids, cohesive forces acting on the liquid molecules are unbalanced.
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When the lower end of a vertical glass tube is placed in a liquid such as water , a concave meniscus forms . Surface tension pulls the liquid column up until there is a sufficient mass of liquid for gravitational forces to overcome the intermolecular forces. Capillary action of water compared to mercury With some pairs of materials, such as mercury and glass, the interatomic forces within the liquid exceed those between the solid and the liquid, so a convex meniscus forms and capillary action works in reverse The edge of the water that sticks up above the water's surface is called a " meniscus ."
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The weight of the liquid column is approximately: W=mg= ρ Vg= ρ g( π r 2 h) Equating the vertical component of the surface tension force to the weight gives: W=F surface 2r 2 π r σ s θ ρ g( π r 2 h)= 2 π r σ s cos θ
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nserv3 - Surface Tension Some consequences of surface...

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