Solid (Concept and Definition)

We explain what solids are, what their properties are and multiple examples. Also, what are the other states of matter.

Solids can be all kinds of sizes, such as sand and rocks. — The key to the physics of solids is in the organization of their particles.

What is a solid?

The solid state (from Latin solidus“solid” or “firm”) is one of the four states of aggregation of matter, along with the liquid, gaseous and plasmatic states, that is, one of the four ways in which matter appears in the universe. But unlike the other three states, the solid They have a rigid structure, resistant to changes in shape and volume and totally lacking in fluidity.because its particles are organized in a very narrow and intense way, within their own three-dimensional structure.

The key to the physics of solids is in the organization of their particles, which can be of three essential types:

Crystalline solids. They are those whose particles are arranged based on a stable and recurring pattern, forming geometric structures called crystals. The latter add to each other to form an even larger pattern, preserving their stability and joint resistance.
Semi-crystalline solids. They are those whose particles have a certain tendency to organize into patterns, but which do not repeat completely, so they do not form crystals.
amorphous solids. They are those whose particles are not ordered in any perceptible way, but rather have an irregular structure, without established patterns.

A substance can acquire a solid state if the pressure and temperature conditions surrounding it are appropriate: a piece of ice is solid, for example, but if it is heated it melts and becomes a liquid state, and vice versa. The same thing happens with certain gases through the process called deposition or reverse sublimation: they go into a solid state forming crystals, as happens with water vapor on a particularly cold day.

Properties of solids

The pencils use solid wood and solid graphite. — Different solids have different degrees of hardness and malleability.

Solids have different physical properties, according to their nature and the composition of their atoms. These properties, in general, are usually the following:

Fixed and defined shape and volumeso they present a certain degree of resistance to deformation and the action of forces on their surface.
High densitycompared to liquids and especially gases, since their particles are very close and cohesive.
Hardness and tenacitythat is, respectively, a certain degree of resistance to penetration, abrasion, cutting and permanent deformation, and also to the propagation of cracks or fissures.
Malleability and ductilitythat is, a certain degree of tolerance to deformation, whether in sheets or threads of the material, which allows them to be used as raw material.
Rigidity, fragility and/or elasticitywhich means that some solids resist deformation (rigid solids) and can break under the action of a force (brittle solids), while others can temporarily lose their shape and recover it once the force acting on them ceases. (elastic solids).
Incompressibilitythat is, solids cannot be compressed.

Examples of solids

Some examples of solid substances of different types are:

Metals, such as iron, silver, gold and possible alloys between them, with the exception of mercury.
Wood and cork, and other materials of plant origin.
Plastics created by humans, such as polystyrene or polyurethane.
Rocks and minerals found underground, such as bauxite or onyx.
Ice, both that formed by water and carbon dioxide (“dry ice”).
Concrete and concrete, formed by mixtures of different binding particles.
Pure carbon crystals, as is the case with diamonds.
Ceramic materials such as earthenware, terracotta or brick.
Decorative stones such as agate, jade, obsidian, among others.
Polymers of plant origin such as cellulose from the leaves and stems of plants.
The bones of the body of vertebrate animals, including humans.
The calcareous shells of bivalves and other marine creatures.
Paper, cardboard and other industrialized derivatives of plant fiber.
Both natural and synthetic fabrics.
Salt and sugar crystals.
Amber and other fossilized resins.
The plaster and clay once they have been left to dry in the open air.
Pearls formed from mother-of-pearl inside the shells of oysters.
The hair and fur of humans and animals.
The chitin shell of insects and other arthropods.
Sand, gravel and other remains of rock erosion.
Plutonium and other long-lived radioactive materials.
Glass in its different types.
The seeds of the plants.
Earth's magma once it has cooled enough.
Composite synthetic materials, such as graphite rayon or acrylonitrile butadiene styrene (ABS).
Some metalloid elements such as silicon, germanium and tellurium.
The cartilage, teeth and nails of the human body.
The rigid layers of frozen terrestrial soil, known as permafrost.
Meteorites and other sidereal objects.

Other states of matter

In addition to the solid state, matter can exist in three other physical states:

The liquid statein which the particles are organized loosely, although not too loosely: somewhere between solids and gases. Liquids are fluid, they have no defined shape (they take on the shape of the container that contains them) and are incompressible. Liquids can become solids through the loss of heat (freezing) or gases through the increase of heat (evaporation).
The gaseous statein which the particles are much more dispersed and separated than in the liquid state, so the substance does not have its own shape and volume, but rather adopts those of the container or environment that contains it. Gases have a weak interaction between their particles, but through increased pressure they can be forced to acquire liquid form (liquefaction).
The plasma statein which the particles are in a gas-like dispersion state, but at the same time are electromagnetically charged (ionized). Plasma is the state of aggregation of the most abundant matter in the universe, whose great and main example is the Sun.

Continue with: Intensive and extensive properties of matter