Q:

What causes surface tension in water?

A:

Quick Answer

The forces that attract water molecules to one another cause surface tension. Water molecules can form hydrogen bonds with each other, and each molecule is attracted to those around it. Molecules at the surface are more attracted to water than the surrounding air, creating surface tension.

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Full Answer

The bonds formed by the water molecules at the surface of a volume of water are strong enough to create some unique effects. When water falls through the air in small amounts, instead of falling in a stream, the water tends to form spherical droplets due to the surface tension created by hydrogen bonds. As the water falls through the air, gravity distorts the sphere into the familiar raindrop shape. The same property allows objects that are light enough to float on the surface of the water without breaking the surface. Some insects, for instance, can run across the surface of still water due to the fact that their weight is insufficient to break the tension created by hydrogen bonds on the surface.

The reason hot water seems to wash clothes and dishes more completely than cold water is due to surface tension. Heated water molecules vibrate and move around, reducing the surface tension and allowing the water to soak into soiled areas of clothing or dishes. Adding soap or detergent further decreases the surface tension, allowing the water to serve as a powerful solvent.

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Related Questions

  • Q:

    What causes surface tension?

    A:

    Surface tension is caused by the attraction between liquid molecules along the surface of the liquid. Most of the molecules in a liquid have several neighboring molecules that they interact with, but the molecules along the surface have no neighboring molecules above them, which increases the strength of the surface molecules with each other.

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  • Q:

    Why do humans float in water?

    A:

    Any body in water floats or sinks depending on the buoyant forces that push it up and the gravity that pulls it down. If the body is heavier than the water it displaces, it sinks. If the water the body displaces is heavier, then the body floats.

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  • Q:

    Why is the buoyant force greatest on something that is submerged?

    A:

    According to Archimedes' principle, buoyant forces are equal to the weight of water an object displaces; therefore, solid objects and watertight hollow vessels displace the greatest amount of water when submerged, maximizing the forces exerted on the object. If the object is less dense than water, it floats to the surface until the weight of the object and the buoyant forces reach equilibrium.

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  • Q:

    How does water evaporate?

    A:

    Water evaporates when molecules at the interface of water and air have enough energy to escape the forces that hold them together in the liquid. Evaporation, along with boiling, is a type of vaporization.

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