Characteristics of States of Matter

We are surrounded by matter. Everything around us, including ourselves, is matter. Although all matter is different, there are a series of characteristics that allow us to classify it according to its state of aggregation, that is, how its molecules are held together.

There are several general criteria for classifying and describing characteristics of states of matter. These are Volume, Shape and Compressibility and Molecular Cohesion. Volume refers to the place a body occupies in space, which can be constant, expand, or contract. The shape is taken into consideration in that the matter in question can acquire the shape of the container that contains it, filling everything, or that it retains its own shape. Compressibility is the ability of a body to be compressed, to occupy a smaller volume. Cohesion refers to the force with which the molecules that make up matter bind together. These bonds can be strong or weak.

Solid state characteristics of matter

In the solid state, the molecules of matter maintain strong forces of cohesion with each other, which allows them to have a shape and volume constant, that is, they retain their own shape, their volume is always the same and they are incompressible, that is, they cannot be compressed and reduced its volume. Due to the cohesion of their molecules, it is common that when they change their shape they reach a point where they break, since their molecules do not slide easily over each other. Examples of this state of matter are metals, wood or plastic.

• Its molecules have very strong cohesion forces, so they are very close together.
• They have a constant shape.
• They have constant volume
• They cannot be compressed.
• Its molecules have little mobility, so, although they can stretch, with the application of force they tend to break.

Characteristics of the liquid state of matter

In the liquid state the cohesion forces between the molecules are lower, allowing them to slide over each other. This sliding capacity of the molecules allows them to maintain a constant volume and at the same time adopt the shape of the container that contains them, filling their gaps. They are also incompressible and cannot reduce their volume. They are fluid, so if their jet is interrupted and then continued, it coalesces to form a single body. Examples of liquids are water, mercury, or volcanic magma.

• Its molecules have strong cohesion forces, so they are very close together, but they can slide over each other.
• They have no definite shape, so they take the shape of the container that contains them.
• They have constant volume
• They cannot be compressed
• Their molecules are highly mobile, so they tend to stick together even if their flow is interrupted or a force is applied.

Characteristics of the gaseous state of matter

In this state of matter, the cohesion of the molecules is very weak, so they are widely separated from each other. They do not have a defined shape, being able to adopt that of the container that contains them. By having weak cohesion forces that tend to repel each other, their volume is not constant either, occupying the largest possible volume, but at the same time it can be compressed to occupy a very small. Examples of matter in a gaseous state are air, cooking gas, or smoke.

• Its molecules have weak cohesion forces, so they are separated and move freely.
• They have no definite shape, so they take the shape of the container that contains them.
• Being so far apart, they do not have a constant volume, so they can be compressed and occupy a smaller volume.
• Due to their molecular separation, they do not conduct electricity.

Characteristics of the plasma state of matter

We hear this word a lot these days, especially when we hear about flat-screen televisions. Plasma is a fourth state of matter. Under certain conditions the plasma state is similar to the gaseous state: its molecular cohesion is very weak, has no definite shape, acquires the shape of the container that contains it and is compressible. Under general conditions, a gas has a low level of ionization, so its molecules are stable and the gas is not a conductor of electricity. The difference with the gaseous state is that in plasma most of its molecules are ionized, which means that they have electrical charges, that when subjected to a magnetic or electric field, they will react by accelerating the particles and causing shocks that will make them release particles subatomic. This phenomenon is used in inventions such as energy-saving lamps, where the filaments produce an electric field that when accelerating the molecules of the mercury vapor inside the lamp, causing them to collide and emit photons, that is, light. This same principle is applied to plasma screens, where each pixel (each color point) is made up of three cells, one for each color (green, red and blue); Each one of them contains neon or xenon gas, which, when subjected to polarization and due to voltage differences, emit photons; the combination of cells that emit photons and the number of emitted photons is what allows any color to be displayed in that pixel.

• They share the general characteristics of gases.
• Its molecules have weak cohesion forces, so they are separated and move freely.
• They have no definite shape, so they take the shape of the container that contains them.
• Being so far apart, they do not have a constant volume, so they can be compressed and occupy a smaller volume.
• Its molecules are ionized, so it is a conductor of electricity.

Another criterion to take into consideration to describe the aggregation states of matter are those of temperature and pressure, since the same body can have different states if the temperature or pressure to which it is subjected varies. An example of this is water. At average temperatures (between 1 ° C and 90 ° C) water is liquid. When the temperature increases, it evaporates and becomes a gaseous state. This evaporation point is in relation to the height above sea level. At sea level, water boils at 100 ° C, while with increasing height, the boiling point decreases; For example, at an altitude of 2,000 meters (as in Mexico City) the boiling point is 92 ° C. On the other hand, water acquires the solid state when it is at very low temperatures. From 0 ° C the water freezes and solidifies. It will stay solid as long as it maintains those low temperatures. As the temperature increases, it returns to the liquid state.

Changes in the aggregation state of matter:

Not all matter changes state in the same way. Some can go from solids to gases without going through the liquid state, for example. The names of the state changes are as follows:

Fusion. It is when a solid goes to the liquid state by the action of heat. This is what happens for example when iron is heated to more than 4,500 ° C.

Solidification. It is what happens when a liquid goes to the solid state, generally when its temperature decreases. This is what happens when the water reaches temperatures of 0 ° or less.

Evaporation. It is when a liquid, after increasing its temperature, becomes a gaseous state. It happens for example with ammonia, which evaporates at room temperature.

Sublimation. It is when a solid goes to the gaseous state without going through the liquid state. This is noticeable with solid CO2 (also called dry ice).

Reverse sublimation. It is the reverse process to the previous one, when a gas passes to the solid state without going through the liquid. This happens for example when iodine vapors are subjected to low temperatures, forming iodine crystals.

Condensation. This happens when a vapor lowers its temperature, taking its liquid form, more stable at that temperature. This is what happens to water vapor when the temperature is reduced to less than 90 or 100 ° C.

Liquefaction. In this process, a matter that under normal conditions of temperature and atmospheric pressure is a gas, is subjected to high pressures and low temperatures, making it take the liquid state. It is the process to which liquefied petroleum gas is subjected to be transported and stored for domestic use in stoves.