Solid: A substance which has the melting point above the room temperature under normal pressure is called a solid. Ex: iron, rubber, plastic etc.
Rigidity in solids: The constituent particles in solids have fixed positions. They can’t move like those in fluids(Liquids & Gases). These particles can only oscillate about there mean positions. This property of solid leads to rigidity. Only due to this the solids have definite shape and volume.
Existence of a state: At the given temperature & pressure, the state of a matter depends upon two factors – the intermolecular forces & thermal energy.
The intermolecular forces are for keeping the constituent particles(molecules or ions or atoms) together.
Thermal energy is responsible for keeping them apart due to which they move faster.
When the temperature is low, the thermal energy is also low. In such a situation intermolecular forces become very strong and they bring the constituent particles very close. Thus, the particles are at fixed positions and a definite shape is formed.
Properties of solids: Solids have following properties:
I. They has definite mass, volume & shape.
II. The intermolecular distances are short.
III. Intermolecular forces are very strong.
IV. The constituent particles have fixed positions and can only oscillate about their mean positions.
Types of solids: Solids can be classified as two types: 1.Crystalline solids & 2.Amorphous solids
1.Crystalline Solids: A solid made up of a large number of crystals is called a crystalline solid. A crystal is an ordered arrangement of particles(molecules, atoms or ions).
Ex: Sodium Chloride(NaCl), quartz etc
2.Amorphous solid: A solid is called amorphous when its constituent particles are irregularly arranged.
Ex: Quartz glass, rubber, plastic etc
Difference between crystalline & amorphous solids:
|Property||Crystalline Solids||Amorphous Solids|
|Shape||Definite Geometrical Shape||Irregular Shape|
|Nature||True solids||Pseudo solids or super cooled liquids|
|Melting Point||Melt at a sharp & characteristic temperature||Melt over a certain range of temperature|
|Heat of fusion||Have definite and characteristic heat of fusion||Don’t have a definite heat of fusion|
|Order of arrangement||Long range order||Only short range order|
|Cleavage Property||Have a clean cleavage when cut||Have irregular cleavage when cut|