liquid state

Chemistry

2022

We explain what the liquid state is and what are the physical characteristics of this state of matter. Examples of liquids.

Water, the quintessential liquid at room temperature.

What is the liquid state?

A liquid state (or simply liquid) is called a state of matter that is considered intermediate between the solid state and the gaseous, since their particles they are close enough together to retain minimal cohesion, while being dispersed enough to allow for fluidity and change of shape.

The particles of a liquid compound are further apart than those of a solid compound, but closer together than those of a gaseous compound. For this reason solid compounds are rigid and gases are dispersed. For a solid to become a liquid it is necessary to supply caloric energy until the fusion. On the other hand, for a gas to become a liquid it is necessary to subtract heat energy from it until the condensation.

Another way to move a compound from one state to another is by varying the conditions of Pressure. For example, if the pressure of a gas is increased, maintaining a certain temperature, its particles will start to get closer together, they will start to interact and it will probably go into a liquid state.

Many compounds remain in a liquid state at normal temperature (25 ⁰C). An example of this is water. But by lowering its temperature by withdrawing heat, can be turned into solid by freezing or solidification. On the other hand, by increasing their temperature by supplying heat, they can become gases by evaporation.

Physical characteristics of the liquid state

Matter in a liquid state has the following fundamental physical characteristics:

  • Shape. Liquids do not have a definite shape, so they acquire that of the container in which they are contained. A glass of water will have the shape of a glass, but a falling drop of water will have a hemispherical shape due to the surface tension of this liquid and the gravity.
  • Fluency. It is a unique characteristic of liquids and gases, which allows them to pass spontaneously from one container to another. This can occur through narrow channels or in a variable shape, since liquid particles, being shapeless, can slip, move and slide.
  • Viscosity. The viscosity of liquids is their endurance to flow and deform. This occurs due to the internal forces of its particles, whose action slows its deformation when it is poured or dropped. Thus, more viscous liquids (such as Petroleum or pitch) flow slowly, as their particles adhere more to each other. In contrast, low-viscosity liquids (such as Water and the alcohol) flow rapidly.
  • Adherence. Liquids can stick to surfaces. An example of this is the drops that remain on objects after being immersed in a liquid.
  • Surface tension. It is a property of the surface of liquids. It consists of the resistance that liquids put to increase their surface area per unit area. This explains why some liquids take certain shapes, such as the spherical shape of water droplets. Also due to surface tension, liquids have resistance to the penetration of objects up to a certain margin, as if it were an elastic layer. For this reason, some insects "walk" on the water and the fallen leaves of the trees remain on it without sinking. Surface tension is directly linked to density.
  • Density. It is the amount of mass that is in a certain volume of a substance. Density and cohesion forces (forces that hold the particles of solids and liquids together) are closely related. Cohesion is lower in liquids than in solids, but it still allows them to occupy a certain volume in space.

Examples of liquid state

Some examples of matter in a liquid state are:

  • Water. The most common substance on our planet and the universal solvent of known matter. It is the liquid par excellence at room temperature. There may be many dissolved substances in it, but its liquidity is preserved.
  • The Mercury. The only metal which at room temperature remains liquid, forming perfect drops of shiny silver color.
  • The urine. Urine is a yellowish liquid with a high content of urea and ammonia, in which toxic waste and metabolic waste are expelled from the body.
  • Milk. It is a nutritive substance that female dogs mammals they secrete through the mammary glands. It is a liquid of color white and high in fat.
  • Gasoline. It is one of the most popular derivatives of Petroleum. It is a substance rich in hydrocarbons and extremely fuel, which makes it an input for motors and other devices that generate movement or electricity.
  • Sulfuric acid. It is a type of acid commonly used in laboratories. It has a very high level of corrosivity and can be very harmful in contact with organic material living.
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