States of matter - Physical and Chemical phenomena

 States of matter - Physical and Chemical phenomena

Matter, depending on temperature and pressure conditions, is in three physical states: solid (s), liquid (l) and gas (g).

In the solid state:

 the structural particles (e.g. molecules) are at small distances from each other, are almost motionless, and the attractive forces that develop between them are strong. Thus, their shape and volume practically do not change, as long as the pressure and temperature conditions do not change.

In the liquid state:

 the structural particles are, compared to the solid state, at greater distances. Also, the attractive forces between the particles are weaker, resulting in greater mobility. Thus liquids have a defined volume, but they do not have a defined shape and each time they take the shape of the container in which they are placed.

Finally, in the gaseous state:

 the structural particles move disorderly in all directions, as cohesive forces are negligible. Thus in gases we have neither a defined shape nor a volume. In fact, significant volume changes occur here, when the temperature or the pressure changes. (figure 1.1)

1.1

Physical and chemical phenomena:

By analogy with the properties of substances, the phenomena (that is, changes in matter) are divided into physical and chemical phenomena.

In natural phenomena:

 only some of the physical properties of substances change, while their chemical composition is preserved.

For example, the evaporation of water is a natural phenomenon, as the only change that occurs is the change in the physical state of the water, from liquid to gas.

In chemical phenomena (chemical reactions):

 we have a radical change in the composition and properties of substances.

For example, when hydrogen burns in air, it turns into water, which has a different composition and different properties (physical and chemical) than hydrogen.