liquid: Wikis

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Encyclopedia

. The dotted line gives the anomalous behaviour of water. The green lines show how the freezing point can vary with pressure, and the blue line shows how the boiling point can vary with pressure. The red line shows the boundary where sublimation or deposition can occur.]]

Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material. The surface is a free surface where the liquid is not constrained by a container.[1]

Characteristics

A liquid's shape is determined by the container it fills. That is to say, liquid particles (normally molecules or clusters of molecules) are free to move about the volume, but they form a discrete surface that may not necessarily be the same as the vessel. The same cannot be said about a gas; it can also be considered a fluid(things that flows, including gas), but it must conform to the shape of the container entirely.

At a temperature below the boiling point, a liquid will evaporate until, if in a closed container, the concentration of the vapors belonging to the liquid reach an equilibrium partial pressure in the gas. Therefore no liquid can exist permanently in a complete vacuum. The surface of the liquid behaves as an elastic membrane in which surface tension appears, allowing the formation of drops and bubbles. Capillarity is another consequence of surface tension. Only liquids can display immiscibility. The most familiar mixture of two immiscible liquids in everyday life is the vegetable oil and water in Italian salad dressing. A familiar set of miscible liquids is water and alcohol. Only liquids display wetting properties. Liquids at their respective boiling point change to gases (except when superheating occurs), and at their freezing points, change to solids (except when supercooling occurs). Even below the boiling point liquid evaporates on the surface. Objects immersed in liquids are subject to the phenomenon of buoyancy, which is also observed in other fluids, but is especially strong in liquids due to their high density. Liquid components in a mixture can often be separated from one another via fractional distillation.

The volume of a quantity of liquid is fixed by its temperature and pressure. Unless this volume exactly matches the volume of the container, (one or more) surfaces are observed. Liquids in a gravitational field, like all fluids, exert pressure on the sides of a container as well as on anything within the liquid itself. This pressure is transmitted in all directions and increases with depth. In the study of fluid dynamics, liquids are often treated as incompressible, especially when studying incompressible flow.

If a liquid is at rest in a uniform gravitational field, the pressure $\ p$ at any point is given by

$\ p=\rho g z$

where:

$\ \rho$ = the density of the liquid (assumed constant)
$\ g$ = gravity
$\ z$ = the depth of the point below the surface.

Note that this formula assumes that the pressure at the free surface is zero, and that surface tension effects may be neglected.

Liquids generally expand when heated, and contract when cooled. Water between 0 °C and 4 °C is a notable exception. Liquids have little compressibility : water, for example, does not change its density appreciably unless subject to pressure of the order of hundreds bar.

Examples of everyday liquids besides water are mineral oil and gasoline. There are also mixtures such as milk, blood, and a wide variety of aqueous solutions such as household bleach. Only six elements are liquid at or about room temperature and pressure: mercury (densest liquid), bromine, francium, caesium, gallium and rubidium.[2] In terms of planetary habitability, liquid water is believed to be a necessity for the existence of life.

Liquid measures

Quantities of liquids are commonly measured in units of volume. These include the litre, not an SI unit, and the cubic metre (m³) which is an SI unit.

Notes

1. White, Frank (2003). Fluid mechanics. New York: McGraw-Hill. pp. p. 4. ISBN 0-07-240217-2.
2. Liquid Elements

Template:State of matter

Wiktionary

Up to date as of January 15, 2010

English

Wikipedia has an article on:

Wikipedia

A liquid—water—flowing out of a bottle

Etymology

< Middle English liquide < Old French liquide < Latin liquidus (fluid, liquid, moist) < liquere (to be liquid, be fluid).

Pronunciation

• IPA: /ˈlɪkwɪd/, SAMPA: /"lIkwId/
• enPR: lɪk'wɪd
• help, file

Noun

 Singular liquid Plural countable and uncountable; plural liquids

liquid (countable and uncountable; plural liquids)

1. (physics) A substance that is flowing, and keeping no shape, such as water; a substance of which the molecules, while not tending to separate from one another like those of a gas, readily change their relative position, and which therefore retains no definite shape, except that determined by the containing receptacle; an inelastic fluid.
A liquid can freeze to become a solid or evaporate into a gas.
2. (phonetics) An l or r sound.

Usage notes

The differentiation of a liquid as an incompressible fluid is not strictly correct, experiment having shown that liquids are compressible to a very limited extend. See fluid.

Translations

The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Help:How to check translations.

liquid (comparative more liquid, superlative most liquid)

 Positive liquid Comparative more liquid Superlative most liquid
1. Flowing freely like water; fluid; not solid and not gaseous; composed of particles that move freely among each other on the slightest pressure.
liquid nitrogen
2. (finance) Of an asset, easily sold or disposed of without losing value.
3. (finance) Of a market, having sufficient trading activity to make buying or selling easy.
The spot foreign exchange market is the world’s largest and most liquid financial market. With a daily trading volume of over \$1.5 trillion, the spot forex market can absorb trading sizes that dwarf the capacity of any other market.

Translations

The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Help:How to check translations.

• liquid in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913
• liquid in The Century Dictionary, The Century Co., New York, 1911

Simple English

File:Drinking
Water is a liquid

A liquid is a form of matter. It is settled between solid and gas. Liquid has an almost-fixed volume, but no set shape.[1]

Every small force makes a liquid change its shape by flowing. Because of that, gravity makes liquids always take the shape of the container. Fluids' components can freely move among themselves.[2]

Fluids that flow slowly have a high viscosity.[3] Some fluids like tar have such a high viscosity that they may seem solid.[4]

It is difficult to compress a liquid.

Examples of liquid are water, oils and blood.

If a liquid is at rest in a uniform gravitational field, the pressure p at any point is given by

p = ρgz

where ρ is the density of the liquid (assumed constant) and z is the depth of the point below the surface. Note that this formula assumes that the pressure at the free surface is zero.

References

1. "Definition of liquid - Chemistry Dictionary". chemicool.com. Retrieved 22 March 2010.
2. "Definition of Liquid". brainyquote.com. Retrieved 22 March 2010.
3. "Teacher Page: Viscosity". spacegrant.hawaii.edu. Retrieved 23 March 2010.
4. "Can you compress a liquid (water)?". physlink.com. Retrieved 23 March 2010.