Solids are substances having definite shape and definite volume. In solids, the particles are
closely packed and the force of attraction between the particles is strong. So solids are rigid. Their
constituent particles (atoms, molecules or ions) have fixed positions and can only vibrate about
their mean positions.
Classification of solids
On the basis of orderly arrangement of particles, solids can be classified into two –
Crystalline solids and Amorphous solids
Crystalline solids
In these solids, the constituent particles have a well ordered arrangement throughout the
solid, i.e., they have a long range order. They consist of a large number of small crystals. They
have a definite geometrical shape, melting point and heat of fusion.
E.g.: Quartz, Diamond, Graphite, fullerene, NaCl, CuSO4.5H2O, ice, naphthalene, SiC etc.
Amorphous solids
In these solids, the ordered arrangement of constituent particles is only at some portions of
the solid, i.e., they have only a short range order. The structure of these solids is similar to that of
liquids. They have no definite geometrical shape, melting point and heat of fusion.
E.g.: Plastic, Glass (quartz glass), Rubber, amorphous silica, coal, charcoal, coke, PVC etc.
Like liquids amorphous solids have a tendency to flow, though very slowly. Therefore,
sometimes these are also called pseudo solids or super cooled liquids.
Glass panes fixed to windows or doors of old buildings are slightly thicker at the bottom
than at the top. This is because the glass flows down very slowly and makes the bottom portion
slightly thicker.
Amorphous solids on heating become crystalline at some temperature. Some glass objects
from ancient civilizations are found to become milky in appearance due to some crystallization.
Anisotropic and isotropic substances
Solids in which the physical properties like electrical conductance, refractive index etc are
different when measured in different directions are said to be anisotropic in nature. This is due to
the different arrangement of particles in different directions. Crystalline solids belong to this class
Solids in which the physical properties are same along any direction are said to be
isotropic in nature. This is due to the irregular arrangement of particles along different directions.
Amorphous solids belong to this class.
Differences between Crystalline solids and Amorphous solids
closely packed and the force of attraction between the particles is strong. So solids are rigid. Their
constituent particles (atoms, molecules or ions) have fixed positions and can only vibrate about
their mean positions.
Classification of solids
On the basis of orderly arrangement of particles, solids can be classified into two –
Crystalline solids and Amorphous solids
Crystalline solids
In these solids, the constituent particles have a well ordered arrangement throughout the
solid, i.e., they have a long range order. They consist of a large number of small crystals. They
have a definite geometrical shape, melting point and heat of fusion.
E.g.: Quartz, Diamond, Graphite, fullerene, NaCl, CuSO4.5H2O, ice, naphthalene, SiC etc.
Amorphous solids
In these solids, the ordered arrangement of constituent particles is only at some portions of
the solid, i.e., they have only a short range order. The structure of these solids is similar to that of
liquids. They have no definite geometrical shape, melting point and heat of fusion.
E.g.: Plastic, Glass (quartz glass), Rubber, amorphous silica, coal, charcoal, coke, PVC etc.
Like liquids amorphous solids have a tendency to flow, though very slowly. Therefore,
sometimes these are also called pseudo solids or super cooled liquids.
Glass panes fixed to windows or doors of old buildings are slightly thicker at the bottom
than at the top. This is because the glass flows down very slowly and makes the bottom portion
slightly thicker.
Amorphous solids on heating become crystalline at some temperature. Some glass objects
from ancient civilizations are found to become milky in appearance due to some crystallization.
Anisotropic and isotropic substances
Solids in which the physical properties like electrical conductance, refractive index etc are
different when measured in different directions are said to be anisotropic in nature. This is due to
the different arrangement of particles in different directions. Crystalline solids belong to this class
Solids in which the physical properties are same along any direction are said to be
isotropic in nature. This is due to the irregular arrangement of particles along different directions.
Amorphous solids belong to this class.
Differences between Crystalline solids and Amorphous solids
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