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Questions and Answers
What characteristic defines the high density of solids?
What characteristic defines the high density of solids?
Which property is not typical of crystalline solids?
Which property is not typical of crystalline solids?
How do amorphous solids differ from crystalline solids?
How do amorphous solids differ from crystalline solids?
What is a defining feature of crystalline solids in regards to heat of fusion?
What is a defining feature of crystalline solids in regards to heat of fusion?
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Which of the following statements is true regarding the compressibility of solids?
Which of the following statements is true regarding the compressibility of solids?
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What property allows amorphous solids to exhibit the same physical characteristics in all directions?
What property allows amorphous solids to exhibit the same physical characteristics in all directions?
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Which of the following statements is true about the melting point of amorphous solids?
Which of the following statements is true about the melting point of amorphous solids?
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What occurs to the volume of amorphous solids when they melt?
What occurs to the volume of amorphous solids when they melt?
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Which of the following best describes the cleavage of amorphous solids?
Which of the following best describes the cleavage of amorphous solids?
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How do the properties of crystalline solids differ from those of amorphous solids?
How do the properties of crystalline solids differ from those of amorphous solids?
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What is a characteristic feature of the electrical and thermal conductivity of amorphous solids?
What is a characteristic feature of the electrical and thermal conductivity of amorphous solids?
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What is the relationship between anisotropy and molecular arrangement in crystalline solids?
What is the relationship between anisotropy and molecular arrangement in crystalline solids?
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Which of the following best describes the symmetry of amorphous solids?
Which of the following best describes the symmetry of amorphous solids?
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What is a space lattice?
What is a space lattice?
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Which of the following describes a unit cell?
Which of the following describes a unit cell?
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In a primitive cubic unit cell, what fraction of an atom is associated with one unit cell from the corner atoms?
In a primitive cubic unit cell, what fraction of an atom is associated with one unit cell from the corner atoms?
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What are the six parameters that define a unit cell?
What are the six parameters that define a unit cell?
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What is true about the atoms in a body-centered cubic (BCC) unit cell?
What is true about the atoms in a body-centered cubic (BCC) unit cell?
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What type of structure does a primitive cubic unit cell exhibit?
What type of structure does a primitive cubic unit cell exhibit?
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Which crystal habit does NOT represent a face-centered cubic (FCC) unit cell?
Which crystal habit does NOT represent a face-centered cubic (FCC) unit cell?
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Study Notes
Isotropy and Anisotropy
- Amorphous solids display isotropic properties, meaning their mechanical, optical, and electrical characteristics are uniform in all directions.
- Crystalline solids exhibit anisotropic behavior, with properties varying based on direction, indicating a structured molecular arrangement.
- Examples of anisotropic behavior include double refraction, where light splits into two rays traveling at different velocities within a crystal.
Properties of Amorphous Solids
- Lack a regular molecular arrangement and have short-range order instead of long-range order.
- Exhibit a range of melting points rather than a sharp melting point, and do not possess a defined heat of fusion.
- Are compressible to some extent and break irregularly when cut with sharp edges, leading to irregular cleavage.
- Do not possess symmetry, and transform without sudden volume change on melting.
Properties of Crystalline Solids
- Characterized by a regular geometric arrangement of molecules or atoms, resulting in long-range order.
- Have a sharp melting point, transitioning abruptly from solid to liquid.
- Exhibit definite heat of fusion, rigidity, and incompressibility, breaking cleanly into flat surfaces when cleaved.
- Possess symmetry and directional dependency, categorizing them as anisotropic.
Nature of Solids
- Solids are defined by high density, low compressibility, rigidity, and fixed shape and volume.
- Composed of closely packed molecules, atoms, or ions held by strong cohesive forces, restricting random movement.
Solid Classification
- Solids are classified into two main types: crystalline and amorphous.
- Crystalline solids have a 3D orderly arrangement, while amorphous solids lack a repeating pattern.
Space Lattice and Unit Cell
- A space lattice is a three-dimensional arrangement of points representing atoms, ions, or molecules in a solid.
- The unit cell is the smallest repeating unit of a crystal structure that maintains the molecule's symmetry.
Unit Cell Parameters
- Comprised of three edges (a, b, c) and three angles (α, β, γ) that may or may not be perpendicular to each other.
- Types of unit cells include Primitive Cubic, Body-Centered Cubic (BCC), and Face-Centered Cubic (FCC).
Primitive Cubic Unit Cell
- Atoms are located solely at the corners of the cube, which are shared among eight adjacent unit cells.
- Each corner atom contributes 1/8th of an atom to the unit cell.
- Total atoms per unit cell is calculated as 8 × 1/8 = 1 atom.
Body-Centered Cubic Unit Cell (BCC)
- Contains atoms at the corners and one atom positioned at the center of the cube.
- The central atom is fully contained within the unit cell, contributing to the overall atomic structure.
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