General Properties of Solids

General Properties of Solids

• Solids are a state of matter where constituents are firmly bound by strong forces.
• Solids have a definite mass, shape, and volume.
• Solids are incompressible and rigid.
• Solids have a close packed arrangement of particles.
• Solids have high density but very slow diffusion rates.
• Solids' constituents have fixed positions and can only vibrate.

Types of Solids

• Crystalline solids have constituents arranged in a definite, repeating order over long distances.
• Crystalline solids usually have flat faces and sharp edges, and sharp melting points.
• Crystalline solids exhibit cleavage along fixed planes.
• They are anisotropic, meaning physical properties vary with direction.
• Crystalline solids include elements and compounds like CaF2, ZnS, diamond, and quartz.
• Amorphous solids lack a regular arrangement of particles; their structure isn't ordered over long distances.
• Amorphous solids do not have sharp melting points and are considered pseudo-solids.
• Amorphous solids exhibit isotropic behavior, with consistent physical properties in all directions.
• Amorphous solids include materials like glass, plastics, and rubber.

Concept Ladder - Matter

• Matter can exist in three main states: solid, liquid, or gas.
• Water exists in three phases: ice (solid), water (liquid), and steam (gas).

Concept Ladder - Isotropic/Anisotropic

• Isotropic materials have identical properties in all directions.
• Anisotropic materials have different properties in different directions, such as wood.

Concept Ladder - Ionic Crystals

• Strong electrostatic forces exist between anions and cations in ionic crystals (like NaCl).

Rack Your Brain - Ice Density

• Ice is less dense than liquid water.

Rack Your Brain - Interfacial Angle

• The angle formed by the perpendiculars of two intersecting faces of a crystal is called the interfacial angle.

Rack Your Brain - Unit Cell of NaCl

• The unit cell of NaCl has a cubic structure.

Q1 - Glass Window Panes

• Glass in old windows is thicker at the bottom as it flows and cools over time, creating an annealing effect. This results in a gradual crystallization, making the glass milky.

Types of Crystals

• Crystalline solids are classified based on the nature of their constituent particles and the binding forces involved.

Bragg's Equation

• Bragg's equation describes the relationship between the wavelength of X-rays and the spacing between crystal planes for diffraction.

Types of Crystalline Solids

• Ionic: Cations and anions, strong electrostatic forces.
• Covalent / Network: Atoms covalently bonded, extremely high melting points (diamond, graphite).
• Molecular: Covalent molecules held by weak forces (intermolecular forces), generally low melting points.
• Metallic: Atoms bonded by metallic bonds with delocalized electrons, good conductors of heat and electricity.

General properties of Crystalline Solids

• X-ray diffraction: Shows regular arrangements.
• Anisotropic behavior: Properties depend on direction (different in different crystallographic directions).
• Cleavage: Tendency to break along specific crystallographic planes.

Unit Cell

• A unit cell is the smallest repeating unit in a crystalline solid.

Types of Unit Cells

• Simple/Primitive: Lattice points only at corners.
• Face-centered: Lattice points at the corners and center of each face.
• Body-centered: Lattice points at the corners and center of the unit cell.
• End-centered: Lattice points at corners and center of two opposite faces.

Symmetry in Crystals

• Center of symmetry: A point in the crystal about which any line passing through it meets identical points at equal distances in opposite directions.
• Axis of symmetry: Imaginary line through which rotation of the crystal results in identical appearance at more than just one point, like 2-, 3-, 4- and 6-fold
• Plane of symmetry: An imaginary plane dividing the crystal into two parts, which reflect each other.

Crystal Systems

• The seven crystal systems are determined based on the lengths and angles of the unit cell edges.
• The crystal systems include: Cubic, Tetragonal, Orthorhombic, Monoclinic, Triclinic, Hexagonal, and Rhombohedral.

Atomic Radius

• Atomic radius is half the distance between two nearest neighboring atoms in a crystal.
• Different formula are used depending upon the cubic structure.

Coordination Number

• The coordination number is the number of nearest neighboring atoms to a particular atom in a crystal.

Density of Lattice Matter

• Density of a crystalline solid is given by the ratio of mass of the unit cell to the volume of the actual unit cell.

Packing Fraction

• Packing fraction is a ratio of space occupied by spheres to total volume of the given unit cell.

Bragg's Equation

• Bragg's equation helps determine crystal structure and inter-planar distances using X-ray diffraction.

Interstitial Voids

• Tetrahedral voids: Located within the unit cell, surrounded by four atoms.
• Octahedral voids: Located within the unit cell, surrounded by six atoms.
• The size of both voids depends on the size of the atoms.

Radius Ratio

• The ratio of the cation radius to the anion radius (r+/r−) is crucial in determining the coordination number and crystal structure of ionic compounds.

Close Packing in Two Dimensions

• Square close packing (each sphere touch 4 others).
• About 52.4% of space is filled.
• Tetrahedral and octahedral voids are present.

Close Packing in Three Dimensions

• Hexagonal close packing (each sphere touch 6 others).
• Cubic close packing (each sphere touch 12 others).
• About 74% of space is filled.

Coordination Number in Close Packing

• Coordination numbers depend on the type of packing (e.g., close packing) and vary for different crystal structures.

Imperfections in Crystals

• Defects in crystal lattice.
• Stoichiometric defects: Defects that do not alter the stoichiometric ratio of the components (e.g., Schottky and Frenkel defects).
• Non-stoichiometric defects: Defects that do alter the stoichiometric ratio (e.g., Metal excess and Metal deficiency).

Electric Properties of Solids

• Piezoelectricity: Electric charge developed in response to mechanical stressing of certain crystals.
• Pyroelectricity: Electric polarization produced when a crystal is heated.
• Ferroelectricity: Polarization remains even after the applied field is removed.
• Antiferroelectricity: Dipoles align in an antiparallel manner.
• Superconductivity: Zero electrical resistance below a certain temperature.

Magnetic Properties of Solids

• Diamagnetic substances: Weakly repelled by magnetic fields (no unpaired electrons).
• Paramagnetic substances: Weakly attracted by magnetic fields (unpaired electrons).
• Ferromagnetic substances: Exhibit strong attraction to magnetic fields, due to spontaneous alignment of moments.
• Antiferromagnetic substances: Opposing magnetic moments cancel each other, resulting in no net magnetism.
• Ferrimagnetic substances: Unequal number of parallel and anti-parallel moments causing a net magnetization.

Crystal Structure

• The arrangement of atoms or molecules in a solid is known as the crystal structure.

This quiz covers the fundamental properties and types of solids. It explores key concepts such as the characteristics of crystalline and amorphous solids, their arrangement of particles, and their physical properties. Test your understanding of solid-state matter and its various forms.