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CBSE Worksheet -01 CLASS - XII CHEMISTRY (The Solid State)
Worksheet - 1
Topic: Solids and their classification.
1. What are fluids? Give examples. [1]
2. Solids are rigid why? [1]
3. How are solids classified? [1]
4. Define the term amorphous with example. [1]
5. The window panes of the old buildings are thick at the bottom. Why? [2]
6. The stability of a crystal is reflected in the magnitude of its melting point. Explain. [2]
7. Graphite is soft and good conductor of electricity. Explain. [2]
8. Ionic solids are good conductors in molten state and in aqueous solutions but not in solid state. Why? [2]
9. Differentiate between amorphous and crystalline solids with reference to
(1) Melting point
(2) Cleavage property
(3) Nature. [3]
10. How are crystalline solids classified on the basis of nature of bonding?Explain with examples. [3]
[ANSWERS]
Ans 1: Substances which flow are fluids e.g. liquids and gases.
Ans 2: Rigidity in solids is due to fixed positions of the constituent particles and their oscillations about their mean positions
Ans 3: Solids may be classified into two categories – crystalline and amorphous.
Ans 4: Amorphous means disordered and random arrangement of particles for example – silica, plastic, rubber
Ans 5: Glass panes of old buildings are thicker at the bottom than at the top as from is an amorphous solid and flows down very slowly and makes the bottom portion thicker.
Ans 6: Melting point of a solid gives an idea about the intermolecular forces acting between particles. When these forces are strong, the melting point is higher and when these forces are weak, low melting point is observed. Higher is the melting point, more stable the solid is.
Ans 7: Graphite is soft and good conductor due to its typical structure here carbon atoms are arranged in different layers and each atom a covalently bonded to three of its neighbouring atoms in the same layer. The fourth electron of each atom is free to move about due to which it conducts electricity. Different layers can slide over the other which makes it a soft solid.
Ans 8: In the solid state, the ions in the ionic solids are not free to move about due to their rigid structure & trong electrostatic forces. Therefore they cannot conduct electricity whereas in molten state and aqueous solution, the ions become free to move about and they conduct electricity.
Ans 9:
Ans 10: Classification of crystalline solids.
1. Molecular solids: The forces operating between molecules are dispersion or London forces, dipole – dipole interactions,hydrogen bonding e.g. CCl4, HCl, ice etc.
2. Ionic solids: The intermolecular forces are coulomibic or electrostatic forces, e.g. NaCl, MgO etc.
3. Metallic solids: The forces operating is metallic bonding e.g. Fe, Cu, Ag etc.
4. Covalent or network solids: The attractive forces are covalent bonding e.g. Diamond, Quartz etc.
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