Solid state

 This is the notes for Solid state.

Solid state

Solids are characterized by following properties 

1. Solids are composed of atoms, ions or molecules.
2. The constituent particles in solid are compactly close to each other.
3. Solids have fixed shape size and volume.
4. Solids are almost incompressible and rigid.
5. Particles of solids diffuse extremely slow into others solids.
6. The particles in solid do not have translatory motion.

Types of solids

• Ionic solids: if the particles of a crystalline solids are ions the solutions are called ionic solids. Example: NaCl, CsCl, MgCl2 etc.
• Covalent solids: if particles of a crystalline solids are atoms which are bounded by network of covalent bonds, the solid is called covalent solid. Example: graphite, diamond etc. 
• Molecular solids: if particles of a crystalline solids are molecules which are held together by vander wall force or hydrogen bonding, the solid is called a molecular solid. Example: Iodine, Ice etc.
• Metallic solids: in metallic solids, metallic cations are arranged in a definite pattern in a pool of free and mobile electrons. Example: various metals and alloys form metallic solid.

Anisotropy and Isotropy

Anisotropy: the solid substances which physical properties such as mechanical strength, optical activity, electrical and thermal conductivity, refractive index, thermal expansion etc are different in different direction are call anisotropic substances and the phenomenon is called anisotropy. Crystalline solid so anisotropic nature. For example sodium chloride, copper sulphate, Oxalic acid copper wire, diamond, graphite etc.

Isotropy: The solid substances whose physical properties such as mechanical strength, optical activity, electrical and thermal conductivity, refractive index, thermal expansion etc are same in all direction are called isotropic solids and the phenomenon is called isotropy. Amorphous substances show isotropic phenomenon.

Difference between crystalline solid and amorphous solid

Water of crystallization: 

 The number of molecules of water associated with one molecule of of anhydrous solid to give hydrated crystal is called number of water of crystallization. Crystals associated with water of crystallization are called hydrated salt.

Efflorescent, hygroscopic and deliquescent solids

Efflorescence: The spontaneous phenomenon in which hydrated solid substances lose one or more water molecule from crystallization at ordinary temperature when exposed to air is called Efflorescence and the chemical substance is called a fluorescent substance. For example: 

CuSO4 .5H2O---------〉 CuSO4 + 5H2O 

                     about 500°C

 Similarly FeSO4 .7H2O, Na2 SO4 .10H2O , etc show efflorescence

Hygroscopic: The spontaneous phenomenon in which a substance absorbs moisture to form hydrated substance on exposure to air is known as hygroscopy and the compound is known as hydroscopic substance. Anhydrous copper sulphate absorbs five molecules of water on exposed to air and becomes pentahydrate copper sulphate. 

 CuSO4 + 5H2O------- 〉CuSO4 .5H2O

Deliquescence: the spontaneous phenomenon in which a substance absorbs moisture till it changes to solution when exposed to air is known as deliquescence and the substance is called deliquescent substance. For example: NaOH, KOH, FeCl3 etc.

Crystallization and crystal growth

Crystallization: The process of forming crystal of a solute is called as crystallization. For example when a saturated solution of copper sulphate is heated up to crystallization point followed by cooling crystal of copper sulphate are obtained.

CuSO4 + H2O-------〉CuSO4 ,( saturated solution) 

CuSO4 ( saturated solution )------〉CuSO4 .5H2O (crystallization crystal)

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