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Why do the window glass of old old build...

Why do the window glass of old old building (a) look milky and (b) become thick at the bottom?

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a. Due to heating during the day and cooling at night, i.e., annealing over a number of years, glass acquires some crystalline character.
b. Glass is not a true solid but a super cooling liquid of high viscosity (called pseudosolid). Therefore, it has the property to flow (i.e., fluidity).
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CENGAGE CHEMISTRY ENGLISH-NCERT BASED EXERCISE-Short Answer Type Questions
  1. Do all metals posses a closed packed structure?

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  2. Why do some substance exist as solids?

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  3. Why do the window glass of old old building (a) look milky and (b) bec...

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  4. Why the melting points of NaF and MgO (990^(@)C and 2640^(@)C) are so ...

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  5. How many types of centred unit cells exist?

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  6. How many types of two-dimensional lattice exist? Why pentagonal lattic...

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  7. How many TVs and OV s occur per unit cell and per atom in a closest pa...

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  8. Where the TVs and OV s are located in a closet packed structure?

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  9. What is the distance between two TVs?

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  10. In an hcp structure, calculate Z("eff)

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  11. In a diamond cubic (dc) structure, calculate Z("eff")

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  12. What is the ratio of (TV//OV)("occupied") in spinel an inverse spinel...

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  13. What is the CN of cation and anion in a corundum structure?

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  14. What is the occurrence of different forms of the same compound called?

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  15. How many allotropic forms of Carbon exist?

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  16. How can a substance be made amorphous?

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  17. Why does ZnO show increased electrical conductivity and turns yellow o...

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  18. Why NiO and FeO are nonstroichiometric with the formula Ni(0.98)O and ...

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  19. Why the defectsof the crystalline solids are called thermodynamic defe...

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  20. Why stoichiometric defects are also called intrinsic defects?

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