Liquid

Liquid

A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. The volume is definite if the temperature and pressure are constant. When a solid is heated above its melting point, it becomes liquid, given that the pressure is higher than the triple point of the substance. Intermolecular (or interatomic or interionic) forces are still important, but the molecules have enough energy to move relative to each other and the structure is mobile. This means that liquid is not definite in shape but rather conforms to the shape of its container. Its volume is usually greater than that of its corresponding solid (the anomalous expansion of water is a notable exception), and it will occupy the entirety of the bottom part of a container, displacing air. A distinctive property of the liquid state is surface tension, leading to wetting phenomena.

Characteristics

The density of a liquid is usually close to that of a solid, and much higher than in a gas. Therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, they are both called fluids. Although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist.

Applications

Liquids have a variety of uses, as lubricants, solvents, and coolants. In hydraulic systems, liquid is used to transmit power. In tribology, liquids are studied for their properties as lubricants. Liquids may also be used in processes such as painting and printing for their ability to evenly distribute themselves over a surface and for their ability to wet surfaces.

See also

• Fluid dynamics
• Phase (matter)
• Supercooling
• Supercritical fluid
• Triple point
• Viscosity

References

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