substances having same crystalline structure are called isomorphous
single substance that crystallizes in two or more forms under different conditions are called polymorphous
true solids
may or may not be isotropic
heat of fusion -definite depends on- arrangement of particles
characteristics shape due to orderly regular long-range arrangement of constituent particle
homogeneous solid in which constituent particles atoms ions are molecules are arranged in a definite repeating pattern
classification
molecular solids
ionic solids
metallic solids
covalent solids
high melting point and depending upon available availability of mobile electrons - conductors / insulators
examples- Diamond graphite and fullerene
MP of diamond 3550 degree Celsius
graphite is used as lubricant &it is also used in Ribbons for printing in computers and typewriters, in lead pencils.
fullerene + potassium---> K35 C60- superconductor at 18 Kelvin, tubes of fullerene + graphite> nanotubes >used as high strength materials, electric conductors, molecular sensors, semiconductors
fullerene- soccer ball- Hollow sphere- C60.
amorphous solids
irregular shape due to short range orderly arrangement
pseudo solids or cooled liquids
isotropic like liquids
heat of fusion is not definite
substances that appear like solids but do not have well developed perfectly ordered crystalline structure