Any change in the state of matter is associated with metamorphoses of temperature and pressure. One substance can be represented in the following aggregate states: solid, liquid, gaseous.
Note that, as the transition proceeds, there is no change in the composition of the substance. The transition of a substance from a liquid to a solid state is accompanied only by a change in the forces of intermolecular interaction, the arrangement of molecules. The transformation from one state to another is called a phase transition.
Melting
This process involves the conversion of a solid into a liquid. Its implementation requires an elevated temperature.
For example, one can observe in nature such a state of matter. Physics easily explains the process of melting snowflakes under the action of spring rays. Small ice crystals that make up the snow, after warming the air to zero, begin to collapse. Melting occurs gradually. First, ice absorbs thermal energy. As the temperature changes, ice is completely transformed into liquid water.
It is accompanied by a significant increase in the particle velocity, thermal energy, and an increase in internal energy.
After reaching an indicator called the melting point, the structure of the solid breaks. The molecules have a lot of freedom, they “jump”, occupying different positions. The molten substance has a greater energy reserve than in the solid state.
Hardening temperature
The transition of a substance from a liquid to a solid state is carried out at a certain temperature value. If heat is removed from the body, then it solidifies (crystallizes).
The hardening temperature is considered one of the most important characteristics.
Crystallization
The transition of a substance from a liquid state to a solid position is called crystallization. When the heat transfer of the liquid ceases, a temperature decreases to a certain value. The phase transition of a substance from a liquid state to a solid in physics is called crystallization. When considering a substance that does not contain impurities, the melting temperature corresponds to the crystallization index.
Both processes proceed gradually. The crystallization process is accompanied by a decrease in the average kinetic energy of the molecules contained in the liquid. The attractive forces due to which particles are held in a strict order inherent in solids increase. After the particles have an ordered arrangement, a crystal will form.
The state of aggregation is the physical form of a substance, presented in a certain range of pressures and temperatures. It is characterized by quantitative properties that are changed at selected intervals:
- the ability of a substance to change shape and volume;
- absence (presence) of long-range or short-range order.
The crystallization process is associated with entropy, free energy, density, and other physical quantities.
In addition to liquids, solids, gaseous form, another aggregate state is isolated - plasma. Gases can pass into it in case of temperature increase at constant pressure.
The framework between the various states of matter is far from always strict. In physics, the existence of amorphous bodies, capable of preserving the structure of a liquid having a small fluidity, has been confirmed. Liquid crystals have the ability to polarize the electromagnetic radiation that passes through them.
Conclusion
In order to describe various states in physics, the definition of the thermodynamic phase is used. Critical phenomena are called states that describe the transformation of one phase into another. Rigid bodies are characterized by maintaining their average position over a long period of time. They will make minor vibrations (with minimal amplitude) around the equilibrium position. Crystals have a certain form, which will change when they transition to a liquid state. Information on boiling (melting) temperatures allows physicists to use transitions from one state of aggregation to another for practical purposes.