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Topic: Surface tension


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  Surface tension - Wikipedia, the free encyclopedia
In physics, surface tension is an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet.
Surface tension is caused by the attraction between the molecules of the liquid by various intermolecular forces.
Surface tension is represented by the symbol σ, γ or T and is defined as the force along a line of unit length where the force is parallel to the surface but perpendicular to the line.
en.wikipedia.org /wiki/Surface_tension   (2941 words)

  
 Hexapedia - Surface tension (via CobWeb/3.1 planetlab1.netlab.uky.edu)   (Site not responding. Last check: 2007-10-12)
Surface tension is caused by the attraction between the molecules of the liquid, due to various intermolecular forces.
At the surface of the liquid, the molecules are pulled inwards by other molecules deeper inside the liquid, but there are no liquid molecules on the outside to balance these forces, so the surface molecules are subject to an inward force of molecular attraction which is balanced by the resistance of the liquid to compression.
Surface tension is measured in newton per meter (Nm), is represented by the symbol σ or γ or T and is defined as the force along a line of unit length perpendicular to the surface or work done per unit area.
www.hexafind.com.cob-web.org:8888 /encyclopedia/surface_tension   (369 words)

  
 PRA: In Can: Surface Tension
Surface energy is quantified in terms of the forces acting on a unit length at the solid-air or the solid-liquid interface.
The numerical difference between the surface tension of a coating and the surface energy of a substrate has a profound effect on the way in which the liquid coating flows out over the substrate and on the strength of the adhesive bond between the substrate and the dry film.
The surface tension of the liquid is then calculated by dividing the surface tension force by the wetted length of the plate.
www.pra.org.uk /technical/testingincansurfacetension.htm   (1854 words)

  
 Surface Tension
Surface tension is a measurement of the cohesive energy present at an interface.
The measurement of surface and interfacial tension as performed by a tensiometer is based on force measurements of the interaction of a probe with the surface of interface of two fluids.
With any of the techniques described herein you may perform interfacial tension measurements just like surface tension measurements by insuring that the bulk of the probe is submersed in the light phase prior to beginning the experiment.
www.ksvinc.com /surface_tension1.htm   (1403 words)

  
 Surface Tension
The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension.
Surface tension is typically measured in dynes/cm, the force in dynes required to break a film of length 1 cm.
The surface tension of water is 72 dynes/cm at 25°C.
hyperphysics.phy-astr.gsu.edu /hbase/surten.html   (694 words)

  
 Surface Tension
As a result, the surface is in tension, which causes it to contract to a minimum area consistent with the mass of material and the container walls.
The surface tension is defined as the force per unit length (usually dynes/cm) in the plane of the surface and is represented by the symbol
Surface tensions for most organic liquids are between 25 and 40 dynes/cm at room temperature, although polyhydric alcohols range up to 65 dynes/cm.
www.pirika.com /chem/TCPEE/ST/ourST.htm   (237 words)

  
 Surface Tension of Water
Surface tension refers to the fact that the surface of the liquid water is pulled tightly together by attractions from inside.
Discuss and conclude that the alcohol and the soap weakened the surface tension of the water at one point and the increased surface tension on the other part of the water contracts the surface and pulls the talcum powder with it.
Because the surface tension was stronger in front of the boat, the boat was moved forward.
www.iit.edu /~smile/ch9510.html   (977 words)

  
 Surface tension, or interfacial tension (, )
The tension acting in the surface of tension is called the surface tension or interfacial tension and is expressed in terms of force per unit length.
In particular, surface tension is the intensive factor in the differential expression for the work required to increase the area of the surface of tension.
The surface tension may, therefore, also be expressed in terms of energy per unit area: it is not, however, in general equal either to the surface energy or to the surface Helmholtz energy per unit area (see §1.2.6).
www.iupac.org /reports/2001/colloid_2001/manual_of_s_and_t/node23.html   (322 words)

  
 Laboratory 1 - Surface Tension
The molecules at the surface of a liquid are subjected to an unbalanced force of molecular attraction as the molecules of the liquid tend to pull those at the surface inward while the vapor does not have as strong an attraction.
Conventionally the tension between the liquid and the atmosphere is called surface tension while the tension between one liquid and another is called interfacial tension.
If you are making a surface tension measurement begin to lower the platform that the beaker is on and add tension to the ring to maintain the ring in position until the ring breaks free of the liquid.
pharmacy.wilkes.edu /kibbeweb/lab2.html   (1660 words)

  
 Surface Tension and Detergent
The surface tension of water is dramatically reduced by the addition of soap or detergent.
Martha Croll ==================================================== The surface tension is determined by what molecules are present in the one or so layers of molecules at the surface of the interface between a liquid and its vapor or air from the atmosphere.
Now molecules that are surface active (surf-act-ants) or detergents have two properties that cause them to reduce the surface tension of water.
www.newton.dep.anl.gov /askasci/phy00/phy00627.htm   (892 words)

  
 SensaDyne: Why Surface Tension Is Important
Fluid surface tension is the tangential force that keeps a fluid together at the air/fluid interface.
A positive spreading coefficient results when the dynamic surface tension of the ink is lower than the surface energy of the substrate.
Surface tension relates directly to a wide range of practical relationships and applications, so that even when a specific surface tension value itself is not of direct interest, it relates directly to another important property of the chemical or formulation.
www.sensadyne.com /why.html   (819 words)

  
 SITA Messtechnik - Basics of Surface Tension   (Site not responding. Last check: 2007-10-12)
Surface tension is a quantity which we often deal with in daily life without realizing it.
Surface tension is created through the attraction of the molecules in liquids to each other.
Therefore, surface tension is defined as the energy needed to increase the surface by a defined value.
www.online-tensiometer.com /oberfl/surface_tension.html   (225 words)

  
 Some Things to Remember About Dynamic Surface Tension
Surface tension describes the cohesive behavior of the surface of the ink or coating.
Therefore, an ink can have a surface tension of 25 dynes/cm, but when it is subject to a dynamic condition, such as a printing press, its “dynamic” surface tension behaves like it has a value of 40 dynes/cm.
The pressurized gas forms bubbles in the liquid, and the differential pressure of the bubbles is measured and equated to the liquid's surface tension.
www.pffc-online.com /mag/paper_things_remember_dynamic/index.html   (680 words)

  
 Surface Tension
The pressure difference between the inside and outside of a bubble depends upon the surface tension and the radius of the bubble.
Surface tension is responsible for the shape of liquid droplets.
Surface tension and adhesion determine the shape of this drop on a twig.
hyperphysics.phy-astr.gsu.edu /hbase/surten2.html   (579 words)

  
 NASA Quest > Space Team Online   (Site not responding. Last check: 2007-10-12)
To study surface tension and the fluid flows caused by differences in surface tension.
Molecules on the surface of a liquid are attracted to their neighbors in such a way as to cause the surface to behave like an elastic membrane.
Surface tension is what allows objects such as needles, razor blades, water bugs, and pepper to float on the surface of liquids.
quest.arc.nasa.gov /space/teachers/mg/9tension.html   (499 words)

  
 Surface Tension   (Site not responding. Last check: 2007-10-12)
Surface tension is measured as the energy required to increase the surface area of a liquid by a unit of area.
The unbalanced attraction of molecules at the surface of a liquid tends to pull the molecules back into the bulk liquid leaving the minimum number of molecules on the surface.
Water does not wet waxed surfaces because the cohesive forces within the drops are stronger than the adhesive forces between the drops and the wax.
www.chem.purdue.edu /gchelp/liquids/tension.html   (418 words)

  
 AllRefer.com - surface tension (Physics) - Encyclopedia
surface tension, tendency of liquids to reduce their exposed surface to the smallest possible area.
The surface then appears to act like an extremely thin membrane, and the small volume of water that makes up a drop assumes the shape of a sphere, held constant when an equilibrium between the internal pressure and that due to surface tension is reached.
Because of surface tension, various small insects are able to skate across the surface of a pond, objects of greater density than water can be made to float, and molten lead when dropped into a cool liquid forms suddenly into shot.
reference.allrefer.com /encyclopedia/S/surfacet.html   (270 words)

  
 Surface Tension
Larger drops of water that sit on a non-wetted surface are not spherical - the shape is the result of the combination of the surface effect with the force of gravity.
The surface is dimpled by their weight until it provides an upward force equal to the weight.
The reason that surface tension affects only small objects is that it is confined to a layer only a few molecules thick.
www.branta.connectfree.co.uk /surface_tension.htm   (1920 words)

  
 Optical control for microfluidic devices powered by surface tension   (Site not responding. Last check: 2007-10-12)
Surface tension, a relatively strong force at micron size scales, would then cause nanoliter volumes of fluid to flow from the cooler areas to warmer areas through thermocapillary action.
Temperature variations arise from light absorption and induce surface tension gradients that drive the flow from the brighter (hotter) to darker (cooler) regions on the substrate.
And because the surface tension effects are strong at the micron scale, they could produce flow rates higher than channel-based microarrays, which must overcome large frictional forces.
gtresearchnews.gatech.edu /newsrelease/surfacetension.htm   (931 words)

  
 Surface Tension
The tension at the surface is 2πrγ, and this must be balanced by a higher pressure p over the diametral plane.
Surface tension encourages the evaporation of small droplets (the added pressure inside a convex surface), and the collapse of small bubbles, for the same reason.
If the surface of a body of water is deformed in a wavelike manner, the higher parts will create a positive pressure from surface tension and their curvature, and the lower parts a negative pressure for the same reason.
www.du.edu /~jcalvert/phys/surftens.htm   (1551 words)

  
 Surface Tension
Surface tension is a measure of the cohesive energy of a liquid.
When one fluid is a gas the tension is termed surface tension, when both fluids are liquids it is termed interfacial tension.
Surface tension is calculated from the force on the balance.
www.ksvinc.com /surface_tension.htm   (257 words)

  
 Surface Tension
The surface tension at that very small area of the straight pin is not large enough to hold the needle afloat.
When the cradle serves to balance the straight pin on the water surface the forces between the water molecules under and around the straight pin are large enough to hold the needle afloat.
However, the surface tension of water is much greater than that of soapy water.
www.iit.edu /~smile/ph9205.html   (745 words)

  
 The Pocket Goniometer
The surface tension of a liquid can be directly measured from the shape of a pendant droplet, which is about to fall off the dispensing tip.
The surface tension can be regarded as a 'contractional force' holding the liquid molecules together like a plastic bag.
It is good practice to check the test liquid from time to time to make sure the surface tension has not decreased because of contamination or aging as a lower surface tension will result in lower contact angles.
www.pocketgoniometer.com /main.php?cont=surfacetension&lang=en   (219 words)

  
 Advanced PCB Resources:Surface Tension
Surface tension is caused by the attraction between
Dimensional analysis shows that the units of surface tension (N·m-1) are equivalent to joules per square metre (J·m-2).
If a surface with surface tension s is expanded by a unit area, then the increase in the surface's stored energy is also equal to s.
www.advancedpcb.com /surface-tension.html   (356 words)

  
 Science Center, Surface Tension
The surface tension of water is caused by the attraction of water molecules to each other.
This occurs because the dish soap reduces the surface tension in the dish, moving the pepper to the edge of the dish.
This demonstrates that because of the water's property of surface tension, small objects are able to float on the surface, but when the surface tension is reduced by the dish soap, the object will sink.
www.simplot.com /education_council/surface_tension.cfm   (150 words)

  
 Surface Tension   (Site not responding. Last check: 2007-10-12)
Surface Tension Lisa C. Ingram Frederick Douglass Middle Academy 8848 S. Marshfield 543 N. Waller Chicago IL 60620 Chicago IL 60644 (312)238-9083 (312)534-6176 Objective: To understand the concept "Surface Tension", through several experiments.
It weakens the surface tension, and the film carries the toothpicks away with it.
Answer: Surface tension builds around the cup, until it is broken with a penny.
www.iit.edu /~smile/ph9509.html   (500 words)

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