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प्रश्न
Under which situations can an amorphous substance change to crystalline form?
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उत्तर
| Property | Crystalline solids | Amorphous solids |
| Shape Melting point | Definite characteristic geometrical shape Melt at a sharp and characteristic temperature | Irregular shape Gradually soften over a range of temperature |
| Cleavage property | When cut with a sharp edged tool. they split into two pieces and the newly generated surfaces are plain and smooth | When cut with a sharp edged tool. they cut into two pieces with irregular surfaces |
| Heat of fusion | They have a definite and characteristic enthalpy of fusion | They do not have definite enthalpy of fusion |
| Anisotropy Nature Order in arrangement of constituent particles | Anisotropic in nature True solids Long range order |
Isotropic in nature Pseudo solids or super cooled liquids Only short range order |
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संबंधित प्रश्न
The relation a ≠ b ≠ c and α ≠ β ≠ γ represents which crystal system?
(A) Orthorhombic
(B) Tetragonal
(C) Triclinic
(D) Monoclinic
Classify the following as amorphous or crystalline solids:
Polyurethane, naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper.
Define the term ‘amorphous’.
‘Stability of a crystal is reflected in the magnitude of its melting points.’ Comment. Collect melting points of solid water, ethyl alcohol, diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules?
Write any two differences between amorphous solids and crystalline solids
Why does sodium chloride on heating with sodium vapours acquire yellow colour?
Assertion: Stability of a crystal is reflected in the magnitude of its melting.
Reason: The stability of a crystal depends upon the strength of the interparticle attractive force.
A crystalline solid ____________.
Which of the following is not a crystalline solid?
The sharp melting point of crystalline solids is due to ______.
Which of the following amorphous solid is used as photovoltaic material for conversion of sunlight into electricity?
Which one of the following is non-crystalline or amorphous?
Amorphous solids are ______.
Which of the following is true about the value of refractive index of quartz glass?
Amorphous solid can also be called:
(i) pseudo solids
(ii) true solids
(iii) supercooled liquids
(iv) supercooled solids
Which of the following features are not shown by quartz glass?
(i) This is a crystalline solid.
(ii) Refractive index is same in all the directions.
(iii) This has definite heat of fusion.
(iv) This is also called super cooled liquid.
The property of crystalline solid is not ______.
Assertion A: Sharp glass edge becomes smooth on heating it upto its melting point.
Reason R: The viscosity of glass decreases on melting.
Choose the most appropriate answer from the options given below.
An ionic solid AB2 isomorphous to the rutile structure (a tetragonal system with the effective number of formula units = 2) has edge lengths of the unit cell of 4Å, 4Å and 7Å. The density of the substance is ______ mg/cc. (if its formula weight is 80. The NA = 6 × 1023 and express your answer in mg/cc using four significant digits.)
