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Give reasons for the following:
The energy required to vapourise one mole of copper is smaller than that of energy required to vapourise one mole of diamond.


The bonding have great influence on the any substance. Copper is a metallic solid having metallic bonds while diamond is a covalent solid having covalent bonds. Metallic bonds are weaker than covalent bonds thus lesser amount of energy is required to break metallic bonds than covalent bonds.
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Explain the following with suitable examples:
Piezoelectric effect (or pressure electricity)

Piezoelectric effect (or pressure electricity):
The word piezoelectricitymeans electricity resulting from pressure.
Insulators do not conduct electricity be the electrons present in them are held tightly to the individual atoms or ions and do not move. However, when an electric field is applied polarisation takes place and newly formed dipoles may align themselves in an ordered manner so that such crystals have a net moment.
When mechanical stress is applied on a polar crystals so as to deform them, electricity produced due to displacement of ions. This is known as piezoelectric effect and electric so this produced is known as Piezo electricity or pressure electricity. Example are : titanium, barium and lead, lead zirconate (PbZrO3), ammonium dihydrogen phosphate and quartz.

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Give reasons for the following:
All metals have metallic bonds but some metals are soft and having low melting points and some are hard and having high melting points.

The strength of metallic bond depends upon the numbr of valence electrons of the metal atom and the magnitude of forces binding these electrons to the nuclei. Thus the strength of metallic bond in different metals may be weak or strong, hence their nature (soft or hard) and their melting points may be different.
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Explain the following with suitable examples:
Antifluorite structure 

Antifluorite structure: 
The antifluorite structure is the opposite arrangment with anion in FCC array with coordination number 8 and cation in the tetrahedral holes with coordination number 4. example of the antifluorite structure are K2O, LiO, Na2O and K2S.
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Give reasons for the following:
Molecular solids are generally soft and easily compressible.

A molecular soild consist of small, non-polar covalent molecule and is held together by landon dispersion forces. thus the force of attraction between the molecule is less de to this reason molecular soilds are generally soft and easily compressible.
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