| Surface tension |
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Related to cohesion is surface tension, a measure of how difficult it is to stretch or break the surface of liquid. Water has a greater surface tension than most other liquids. At the interface between water and air is an ordered arrangement of water molecules, hydrogen-bonded to one another and to the water below. This makes the water behave as though coated with an invisible film. You can observe the surface tension of water by gently laying a dry paper clip on the surface of some still water. If you’re careful enough, the clip will rest on the surface, pushing the surface down slightly but not sinking. In a more biological example, some animals can stand, walk, or run on water without breaking the surface. This elastic tendency found at the surface of a liquid, such as water, is known as surface tension. |
The high surface tension of water, resulting from the collective strength of its hydrogen bonds, allows the water strider to walk on the surface of a pond. The slight depression in the surface is caused by the weight of the water strider. |
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