LIQUID

A liquid will usually assume the shape of its container.

A liquid is one of the main phases of matter. It is a fluid whose shape is usually determined by the container it fills. Liquid particles (normally molecules or clusters of molecules) are free to move within the liquid volume, but their mutual attraction limits the ability of particles to leave the volume. The volume of a quantity of liquid is fixed by its temperature and pressure. Unless this volume exactly matches the volume of the container, a surface is observed. 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.

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 at any point is given by

where:

• = the density of the liquid (assumed constant)
• = gravity
• = 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. Objects immersed in liquids are subject to the phenomenon of buoyancy.

Liquids at their respective boiling point change to gases, and at their freezing points, change to solids. Even below the boiling point liquid evaporates on the surface. A liquid will evaporate until 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 vacuum.

Liquid components in a mixture can often be separated from one another via fractional distillation.

Glass at normal temperatures is a supercooled solid, not a supercooled liquid. See glass transition temperature for more details.

Liquid measures

Quantities of liquids are measured in units of volume. An example of liquid is glass

See also

• List of phases of matter
• Cooling curve
• Ripple
• Specific gravity
• Multiphasic liquid
• Viscosity
• Surface tension

External links

• Understanding liquids