Q: Why do we feel cold after taking a bath? Answer: Water absorbs heat from our body for the process of evaporation. Consequently, we experience a sensation of coldness.
Q: Why does alcohol evaporate faster than water?
Answer: The intermolecular forces in alcohol are weaker than those in water; as a result, it evaporates more rapidly.
Q: State any two factors that increase the rate of evaporation of a liquid.
Answer: Increase in surface area and temperature.
Q: Give one example of a molecular solid. Answer: Iodine or Ice.
Q: Give one example of an ionic solid. Answer: Sodium Chloride.
Q: What is a crystal lattice? Answer: A regular three-dimensional arrangement of points in crystalline solids—wherein each point represents a constituent particle—is called a crystal lattice.
Q: Differentiate between metallic solids and molecular solids. Answer: Metallic Solids: These consist of countless positive ions held together by a “sea” of electrons. The forces binding their constituent particles are known as metallic bonds.
Molecular Solids: Their constituent particles are molecules. These molecules are held together by weak Van der Waals forces.
Q: What is a unit cell? How is it characterized? Answer: The smallest group of points within a crystal lattice that, through repetition, can generate the entire lattice is called a unit cell. A unit cell is defined by the lengths of its three edges and the angles between them.
Q: How many atoms are present in an FCC unit cell? Answer: Four.
Q: How many atoms are present in a Simple Cubic and a BCC unit cell? Answer: There is 1 atom in a Simple Cubic unit cell and 2 atoms in a BCC unit cell.
Q: What is the difference between glass and quartz?
Answer – Glass is a supercooled liquid, whereas quartz is a crystalline solid.
Q. – Why do ionic solids have high melting points?
Answer – In ionic solids, the bonding between cations and anions is strong and directional. Consequently, ionic solids are hard and possess high melting points.
Q. – Write the differences between crystalline solids and amorphous solids. Crystalline Solids: 1. Their constituent particles are arranged in a regular order. 2. They are anisotropic in nature. 3. The values of physical properties are the same in all directions. 4. Crystalline solids have a definite melting point. Amorphous Solids: 1. Their constituent atoms or ions are not arranged in any specific order. 2. They are isotropic in nature. 3. The values of physical properties vary in different directions.
Q. – Why is glass considered a supercooled liquid? Explain. Answer: Glass possesses the property of flowing very slowly. It exhibits the characteristic of high viscosity.
Q. – Explain the Frenkel defect. Answer – Frenkel Defect: 1. When an ion shifts from its regular lattice site to occupy an interstitial void within the lattice, this defect in the crystal is termed a Frenkel defect. 2. The Frenkel defect is exhibited by compounds in which there is a significant difference in size between the cations and the anions. 3. In this defect, the cation leaves its original lattice site and moves into an interstitial void. This defect does not alter the density of the solid.
