Surface Tension

Essay by Zorric SiaHigh School, 11th gradeA, January 1997

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Surface Tension

My problem was to find out how to test or measure surface tension. I think the

reason of some of the force in surface tension is cohesion and gravity. Surface Tension is

the condition existing at the free surface of a liquid, resembling the properties of an

elastic skin under tension. The tension is the result of intermolecular forces exerting an

unbalanced inward pull on the individual surface molecules; this is reflected in the

considerable curvature at those edges where the liquid is in contact with the wall of a

vessel. Because of this property, certain insects can stand on the surface of water. A razor

blade can also be supported by the surface tension of water. The razor blade is not

floating: if pushed through the surface, it sinks through the water. More specifically, the

tension is the force per unit length of any straight line on the liquid surface that the

surface layers on the opposite sides of the line exert upon each other.

The tendency of

any liquid surface is to become as small as possible as a result of this tension, as in the

case of mercury, which forms an almost round ball when a small quantity is placed on a

horizontal surface. The near-perfect spherical shape of a soap bubble, which is the result

of the distribution of tension on the thin film of soap, is another example of this force;

surface tension alone can support a needle placed horizontally on a water surface.

Surface tension depends mainly upon the forces attraction between the particles

within the given liquid and also upon the gas, solid, or liquid in contact with it.

The molecules in a drop of water, for example, attract each other weakly. Water

molecules well inside the drop may be thought...