1.
What is a crystalline solid?
Correct Answer
A. A solid that has a regular and 3D arrangement of constituent particles.
Explanation
A crystalline solid is a type of solid that has a regular and 3D arrangement of its constituent particles. This means that the particles are arranged in a repeating pattern, forming a crystal lattice structure. This regular arrangement gives crystalline solids their characteristic properties such as cleavage, anisotropy, and the ability to form well-defined crystal faces. In contrast, a solid with an irregular arrangement of particles would be considered amorphous, lacking the long-range order found in crystalline solids. Therefore, the correct answer is "A solid that has a regular and 3D arrangement of constituent particles."
2.
What is true regarding amorphous solids?
Correct Answer
D. All of the above
Explanation
Amorphous solids have short-range order, meaning that the particles are arranged in a somewhat organized manner but do not have a long-range repeating pattern. Glasses are an example of amorphous solids, as they do not have a definite lattice pattern. Therefore, all of the statements mentioned in the options are true regarding amorphous solids.
3.
What are the main types of crystalline solids?
Correct Answer
D. All of the above
Explanation
The main types of crystalline solids are ionic solids, metallic solids, and molecular solids. Ionic solids are composed of positive and negative ions held together by electrostatic forces. Metallic solids are made up of a lattice of metal atoms held together by metallic bonds. Molecular solids consist of individual molecules held together by intermolecular forces. Therefore, the correct answer is "All of the above" as it includes all three types of crystalline solids mentioned.
4.
In Crystalline Silicon, each atom is ________________ bonded to _________ neighbors.
Correct Answer
A. Tetrahedrally; four
Explanation
In Crystalline Silicon, each atom is tetrahedrally bonded to four neighbors. This means that each silicon atom forms four chemical bonds with four neighboring silicon atoms, resulting in a tetrahedral arrangement. This arrangement is characteristic of the crystal structure of silicon, where each silicon atom is surrounded by four other silicon atoms, forming a three-dimensional lattice.
5.
What are quasicrystals?
Correct Answer
A. A type of solid that lacks long-range order.
Explanation
Quasicrystals are a type of solid that lack long-range order. Unlike regular crystals, which have a repeating pattern, quasicrystals have a unique and complex arrangement of atoms that do not repeat. This lack of long-range order gives quasicrystals their distinct properties and makes them different from other types of solids.
6.
Long-range order property in crystals is also known as
Correct Answer
C. Translational periodicity
Explanation
Translational periodicity refers to the repeating pattern of atoms or molecules in a crystal lattice. It describes the regular arrangement of particles in a crystal, where each unit cell is identical and can be translated to fill the entire crystal structure. This property is essential for the formation and stability of crystals, as it determines their unique geometric shapes and physical properties. Therefore, the correct answer is "translational periodicity."
7.
Most solid materials are found in nature in what form?
Correct Answer
C. Polycrystalline form
Explanation
Most solid materials are found in nature in polycrystalline form. This means that they consist of multiple small crystals or grains that are randomly oriented and interconnected. Polycrystalline materials have a more complex structure compared to single crystals, which have a uniform arrangement of atoms. The presence of multiple grains in polycrystalline materials can affect their mechanical, electrical, and thermal properties. Therefore, it is common to find solid materials in polycrystalline form in nature.
8.
Which of the following properties best describes single crystals of metals?
Correct Answer(s)
A. Soft
B. Malleable
Explanation
Pure metallic compounds are soft and malleable due to a "sea" of unbonded/ delocalized electrons within their structure. This "sea" allows for malleability and also conductivity. The addition of other compounds, like carbon, to pure metals, creates metal alloys. The presence of carbon in metal alloys disrupts the delocalized electron sea, resulting in hardness and strength.
9.
What are the properties of crystalline solids?
Correct Answer
D. All of the above
Explanation
The properties of crystalline solids include the ability to diffract X-rays, having sharp melting points, and having well-defined edges. These properties are a product of the well-organized, tertiary bonding within the compound.
10.
_____________ crystals are less ductile and have low electrical conductivity.
Correct Answer
B. Non-metallic
Explanation
Non-metallic crystals are less ductile and have low electrical conductivity. This is because non-metallic elements tend to have high electronegativity, which means they attract electrons strongly and form covalent bonds. These covalent bonds result in a rigid lattice structure, making the crystals less malleable or ductile. Additionally, non-metallic elements usually have a high ionization energy, which makes it difficult for them to lose electrons and conduct electricity effectively. Therefore, non-metallic crystals exhibit these properties of being less ductile and having low electrical conductivity.