Liquids and solids are both highly compressible liquids

Liquids have little compressibility. Water, for example, will compress by only This incompressible nature makes a liquid suitable for transmitting hydraulic power, because very little of the energy is lost in the form of compression.

Because liquids have little elasticity they can literally be pulled apart in areas of high turbulence or a dramatic change in direction, such as the trailing edge of a boat propeller or a sharp corner in a pipe.

A liquid in an area of low pressure vacuum vaporizes and forms bubbles, which then collapse as they enter high pressure areas. This causes liquid to fill the cavities left by the bubbles with tremendous localized force, eroding any adjacent solid surface. In a gravitational field , liquids 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. If a liquid is at rest in a uniform gravitational field, the pressure, p , at any depth, z , is given by. Note that this formula assumes that the pressure at the free surface is zero, and that surface tension effects may be neglected.

Objects immersed in liquids are subject to the phenomenon of buoyancy. Buoyancy is also observed in other fluids, but is especially strong in liquids due to their high density.

Unless the volume of a liquid exactly matches the volume of its container, one or more surfaces are observed. The surface of a liquid behaves like an elastic membrane in which surface tension appears, allowing the formation of drops and bubbles. Surface waves , capillary action , wetting , and ripples are other consequences of surface tension. In a confined liquid , defined by geometric constraints on a nanoscopic scale, most molecules sense some surface effects, which can result in physical properties grossly deviating from those of the bulk liquid.

A free surface is the surface of a fluid that is subject to both zero perpendicular normal stress and parallel shear stress, such as the boundary between, e. The liquid level as in, e. It may be measured with a level sensor. Viscosity measures the resistance of a liquid which is being deformed by either shear stress [14] or extensional stress. When a liquid is supercooled towards the glass transition , the viscosity increases dramatically.

The liquid then becomes a viscoelastic medium that shows both the elasticity of a solid and the fluidity of a liquid, depending on the time scale of observation or on the frequency of perturbation. At a temperature below the boiling point , any matter in liquid form will evaporate until the condensation of gas above reach an equilibrium. At this point the gas will condense at the same rate as the liquid evaporates.

Thus, a liquid cannot exist permanently if the evaporated liquid is continually removed. A liquid at its boiling point will evaporate more quickly than the gas can condense at the current pressure. A liquid at or above its boiling point will normally boil, though superheating can prevent this in certain circumstances. At a temperature below the freezing point, a liquid will tend to crystallize , changing to its solid form.

Unlike the transition to gas, there is no equilibrium at this transition under constant pressure, so unless supercooling occurs, the liquid will eventually completely crystallize.

Note that this is only true under constant pressure, so e. For the opposite transition from solid to liquid, see melting. The phase diagram explains why liquids do not exist in space or any other vacuum.

Since the pressure is zero except on surfaces or interiors of planets and moons water and other liquids exposed to space will either immediately boil or freeze depending on the temperature. In regions of space near the earth, water will freeze if the sun is not shining directly on it and vapourize sublime as soon as it is in sunlight.

If water exists as ice on the moon, it can only exist in shadowed holes where the sun never shines and where the surrounding rock doesn't heat it up too much.

At some point near the orbit of Saturn, the light from the sun is too faint to sublime ice to water vapour. This is evident from the longevity of the ice that composes Saturn's rings.

Liquids can display immiscibility. The most familiar mixture of two immiscible liquids in everyday life is the vegetable oil and water [16] in Italian salad dressing. In a liquid, atoms do not form a crystalline lattice, nor do they show any other form of long-range order. This is evidenced by the absence of Bragg peaks in X-ray and neutron diffraction.

Under normal conditions, the diffraction pattern has circular symmetry, expressing the isotropy of the liquid. In radial direction, the diffraction intensity smoothly oscillates.

The oscillations of S q express the near order of the liquid, i. A more intuitive description of these correlations is given by the radial distribution function g r , which is basically the Fourier transform of S q. It represents a spatial average of a temporal snapshot of pair correlations in the liquid. If K is frequency independent then the liquid behaves as a linear medium , so that sound propagates without dissipation and without mode coupling.

In reality, any liquid shows some dispersion: In normal liquids, most of this cross over takes place at frequencies between GHz and THz, sometimes called hypersound.

At sub-GHz frequencies, a normal liquid cannot sustain shear waves: This is sometimes seen as the defining property of a liquid. According to the Kramers-Kronig relation , the dispersion in the sound velocity given by the real part of K or G goes along with a maximum in the sound attenuation dissipation, given by the imaginary part of K or G. According to linear response theory , the Fourier transform of K or G describes how the system returns to equilibrium after an external perturbation; for this reason, the dispersion step in the GHz..

On supercooling a liquid towards the glass transition, the crossover from liquid-like to solid-like response moves from GHz to MHz, kHz, Hz, This is the microscopic explanation for the above-mentioned viscoelastic behaviour of glass-forming liquids.

Descriptions of viscosity in terms of molecular "free space" within the liquid [19] were modified as needed in order to account for liquids whose molecules are known to be "associated" in the liquid state at ordinary temperatures. When various molecules combine together to form an associated molecule, they enclose within a semi-rigid system a certain amount of space which before was available as free space for mobile molecules.

Thus, increase in viscosity upon cooling due to the tendency of most substances to become associated on cooling. Similar arguments could be used to describe the effects of pressure on viscosity, where it may be assumed that the viscosity is chiefly a function of the volume for liquids with a finite compressibility.

An increasing viscosity with rise of pressure is therefore expected. In addition, if the volume is expanded by heat but reduced again by pressure, the viscosity remains the same. The local tendency to orientation of molecules in small groups lends the liquid as referred to previously a certain degree of association.

This association results in a considerable "internal pressure" within a liquid, which is due almost entirely to those molecules which, on account of their temporary low velocities following the Maxwell distribution have coalesced with other molecules.

The internal pressure between several such molecules might correspond to that between a group of molecules in the solid form.

From Wikipedia, the free encyclopedia. For other uses, see Liquid disambiguation. Surface tension Capillary action. This section possibly contains original research. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. October Learn how and when to remove this template message.

This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. Workman Publishing, p. Van Nostrand Company p. Huang — American Institute of Aeronautics and Astronautics p. Surfactants are commonly found in soaps and detergents. Solvents like alcohol are often used as antimicrobials. They are found in cosmetics, inks , and liquid dye lasers.

They are used in the food industry, in processes such as the extraction of vegetable oil. Liquids tend to have better thermal conductivity than gases, and the ability to flow makes a liquid suitable for removing excess heat from mechanical components. The heat can be removed by channeling the liquid through a heat exchanger , such as a radiator , or the heat can be removed with the liquid during evaporation.

During perspiration , sweat removes heat from the human body by evaporating. In the heating, ventilation, and air-conditioning industry HVAC , liquids such as water are used to transfer heat from one area to another. Liquid is the primary component of hydraulic systems, which take advantage of Pascal's law to provide fluid power.

Devices such as pumps and waterwheels have been used to change liquid motion into mechanical work since ancient times. Oils are forced through hydraulic pumps , which transmit this force to hydraulic cylinders. Hydraulics can be found in many applications, such as automotive brakes and transmissions , heavy equipment , and airplane control systems.

Various hydraulic presses are used extensively in repair and manufacturing, for lifting, pressing, clamping and forming. Liquids are sometimes used in measuring devices.

A thermometer often uses the thermal expansion of liquids, such as mercury , combined with their ability to flow to indicate temperature. A manometer uses the weight of the liquid to indicate air pressure. Quantities of liquids are measured in units of volume. The volume of a quantity of liquid is fixed by its temperature and pressure. Liquids generally expand when heated, and contract when cooled. Liquids have little compressibility. Water, for example, will compress by only This incompressible nature makes a liquid suitable for transmitting hydraulic power, because very little of the energy is lost in the form of compression.

The banging of pipes, called water hammer , occurs when a valve is suddenly closed, creating a huge pressure-spike at the valve that travels backward through the system at just under the speed of sound. Another phenomenon caused by liquid's incompressibility is cavitation. Because liquids have little elasticity they can literally be pulled apart in areas of high turbulence or a dramatic change in direction, such as the trailing edge of a boat propeller or a sharp corner in a pipe.

In a gravitational field , liquids 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. If a liquid is at rest in a uniform gravitational field, the pressure, p , at any depth, z , is given by. Note that this formula assumes that the pressure at the free surface is zero, and that surface tension effects may be neglected.

Objects immersed in liquids are subject to the phenomenon of buoyancy. Buoyancy is also observed in other fluids, but is especially strong in liquids due to their high density. Unless the volume of a liquid exactly matches the volume of its container, one or more surfaces are observed. The surface of a liquid behaves like an elastic membrane in which surface tension appears, allowing the formation of drops and bubbles. Surface waves , capillary action , wetting , and ripples are other consequences of surface tension.

In a confined liquid , defined by geometric constraints on a nanoscopic scale, most molecules sense some surface effects, which can result in physical properties grossly deviating from those of the bulk liquid.

Viscosity measures the resistance of a liquid which is being deformed by either shear stress [14] or extensional stress. When a liquid is supercooled towards the glass transition , the viscosity increases dramatically.

At this point the gas will condense at the same rate as the liquid evaporates. Thus, a liquid cannot exist permanently if the evaporated liquid is continually removed. A liquid at its boiling point will evaporate more quickly than the gas can condense at the current pressure. A liquid at or above its boiling point will normally boil, though superheating can prevent this in certain circumstances. At a temperature below the freezing point, a liquid will tend to crystallize , changing to its solid form.

Unlike the transition to gas, there is no equilibrium at this transition under constant pressure, so unless supercooling occurs, the liquid will eventually completely crystallize. Note that this is only true under constant pressure, so e. For the opposite transition from solid to liquid, see melting.

The phase diagram explains why liquids do not exist in space or any other vacuum. Since the pressure is zero except on surfaces or interiors of planets and moons water and other liquids exposed to space will either immediately boil or freeze depending on the temperature. In regions of space near the earth, water will freeze if the sun is not shining directly on it and vapourize sublime as soon as it is in sunlight. If water exists as ice on the moon, it can only exist in shadowed holes where the sun never shines and where the surrounding rock doesn't heat it up too much.

At some point near the orbit of Saturn, the light from the sun is too faint to sublime ice to water vapour. This is evident from the longevity of the ice that composes Saturn's rings. Liquids can display immiscibility. The most familiar mixture of two immiscible liquids in everyday life is the vegetable oil and water [16] in Italian salad dressing. In a liquid, atoms do not form a crystalline lattice, nor do they show any other form of long-range order.

This is evidenced by the absence of Bragg peaks in X-ray and neutron diffraction. Under normal conditions, the diffraction pattern has circular symmetry, expressing the isotropy of the liquid. In radial direction, the diffraction intensity smoothly oscillates. The oscillations of S q express the near order of the liquid, i. A more intuitive description of these correlations is given by the radial distribution function g r , which is basically the Fourier transform of S q.

It represents a spatial average of a temporal snapshot of pair correlations in the liquid. If K is frequency independent then the liquid behaves as a linear medium , so that sound propagates without dissipation and without mode coupling.

In reality, any liquid shows some dispersion: In normal liquids, most of this cross over takes place at frequencies between GHz and THz, sometimes called hypersound. At sub-GHz frequencies, a normal liquid cannot sustain shear waves: This is sometimes seen as the defining property of a liquid.

According to the Kramers-Kronig relation , the dispersion in the sound velocity given by the real part of K or G goes along with a maximum in the sound attenuation dissipation, given by the imaginary part of K or G. According to linear response theory , the Fourier transform of K or G describes how the system returns to equilibrium after an external perturbation; for this reason, the dispersion step in the GHz..

THz region is also called structural relaxation. According to the fluctuation-dissipation theorem , relaxation towards equilibrium is intimately connected to fluctuations in equilibrium. The density fluctuations associated with sound waves can be experimentally observed by Brillouin scattering. On supercooling a liquid towards the glass transition, the crossover from liquid-like to solid-like response moves from GHz to MHz, kHz, Hz, This is the microscopic explanation for the above-mentioned viscoelastic behaviour of glass-forming liquids.