Liquid
From Halbeeg, the open encyclopedia · Af-Soomaali
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A liquid is one of the ordinary states of matter, positioned between solid and gas. A liquid has a volume that remains constant, but lacks a fixed shape: it takes the shape of the container into which it is poured, and forms a level surface when at rest.
The small parts of a liquid (atoms or molecules) are close to one another, as in solids, but their bonds are not rigid or permanent. For this reason they can move, making the liquid flow. Compressing a liquid is difficult because the space between the parts is already small.
Key Properties
The most commonly measured properties of liquids include density, which is the mass per unit volume; viscosity, which describes how a liquid resists flow—the viscosity of oil is higher than that of water; and surface tension, which arises from the attraction between molecules and causes small drops to form into spherical shapes.
Change of State
When a solid's temperature reaches its melting point, it becomes a liquid. When a liquid is heated to its boiling point, it turns into gas. The reverse process is called condensation: gas becomes liquid, and liquid becomes solid (freezing). The temperature of the air or environment affects these transitions; for example, in mountainous regions where the air is very cold, water can freeze at a temperature lower than normal.
Pressure and Motion
A liquid in a container exerts pressure on the walls and bottom, and this pressure increases with depth. An object placed in a liquid experiences an upward force equal to the weight of the liquid it displaces—a principle known as Archimedes' principle, which explains why ships float. The study of the motion of liquids and gases is called fluid mechanics.
Importance and Uses
Water is the most common liquid on Earth and is a chemical essential to life, since the processes of living things occur in water-based solutions. Industries use liquids for dissolving materials, cooling machines, transmitting power (hydraulics), and as fuel for vehicles. Some liquids, such as mercury, are liquid at room temperature.