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Total Categories: 6
At the microscopic level, a crystal is characterized by a disordered arrangement of atoms, molecules, or ions.
Answer: False
This statement is incorrect. Crystals are fundamentally defined by a highly ordered, repeating arrangement of atoms, molecules, or ions, forming a crystal lattice. Disordered arrangements are characteristic of amorphous solids.
The macroscopic geometric shape of single crystals, characterized by flat faces, is a direct reflection of their underlying ordered microscopic structure.
Answer: True
The external geometric form of single crystals, including their flat faces and angles, is a macroscopic manifestation of the underlying, highly ordered, and repeating atomic arrangement within the crystal lattice.
The word 'crystal' is derived from an Ancient Greek term meaning 'frozen water' or 'rock crystal'.
Answer: True
The term 'crystal' originates from the Ancient Greek word 'krustallos', which referred to both ice and rock crystal, itself derived from 'kruos' meaning 'icy cold' or 'frost'.
Snowflakes, diamonds, and table salt are examples of substances that do not exhibit crystalline structures.
Answer: False
This statement is false. Snowflakes, diamonds, and table salt (sodium chloride) are all common examples of substances that exhibit highly ordered crystalline structures.
The 'Patterns in nature' navigation box lists 'Crystal' under 'Biological processes' as a cause of pattern formation.
Answer: False
This statement is false. The 'Patterns in nature' navigation box categorizes 'Crystal' under 'Physics' as a cause of pattern formation, not 'Biological processes'.
What is the fundamental characteristic defining a crystal at the microscopic level?
Answer: A highly ordered, repeating arrangement of atoms, molecules, or ions.
Crystals are fundamentally defined by the ordered, repeating arrangement of their constituent particles (atoms, molecules, or ions) in a three-dimensional lattice structure.
The word 'crystal' originates from the Ancient Greek word 'krustallos', which referred to:
Answer: Ice and rock crystal
The etymological root of the word 'crystal' is the Ancient Greek term 'krustallos', which denoted both ice and rock crystal.
According to the source, what does the 'Crystal' entry under 'Physics' causes in the 'Patterns in nature' navigation box signify?
Answer: Crystals are a pattern caused by physical processes.
The 'Patterns in nature' navigation box categorizes 'Crystal' under 'Physics', indicating that crystal formation is considered a pattern arising from physical processes.
Crystallography is the scientific discipline primarily focused on the study of amorphous solids and their formation processes.
Answer: False
This statement is incorrect. Crystallography is the scientific discipline dedicated to the study of crystals and their atomic structure, not amorphous solids. The study of amorphous solids falls under materials science and solid-state physics.
A 'unit cell' is the smallest repeating unit that, when stacked, builds the entire crystal structure.
Answer: True
This statement is correct. The unit cell is defined as the smallest repeating structural unit in a crystal lattice, which, when translated in three dimensions, generates the entire crystal structure.
The symmetry of crystals is unlimited, as any geometric arrangement can form a stable crystal lattice.
Answer: False
This statement is incorrect. The symmetry of crystals is limited by the geometric constraint that unit cells must tile space without gaps. This restriction leads to a finite number of possible crystallographic symmetries.
There are exactly 7 crystallographic space groups, which are further organized into 219 broader categories.
Answer: False
This statement is incorrect. There are 7 crystal systems, which are broader categories. These systems are further organized into 230 distinct crystallographic space groups, not 7 space groups and 219 categories.
The cubic crystal system is characterized by a high degree of symmetry, often resulting in cube-shaped or rectangular box unit cells.
Answer: True
This statement is correct. The cubic crystal system is known for its high symmetry, and its unit cells are indeed cubic or rectangular boxes, reflecting this symmetry.
Crystallization is the process where amorphous solids transform into ordered crystalline structures.
Answer: False
This statement is incorrect. Crystallization is the process by which ordered crystalline structures form from a liquid, gas, or solution. While amorphous solids can sometimes be converted to crystalline forms (e.g., through annealing), crystallization itself is the formation of crystals, not necessarily a transformation from an amorphous state.
X-ray diffraction is a primary technique used in crystallography to determine the precise arrangement of atoms within a crystal.
Answer: True
This statement is correct. X-ray diffraction is a fundamental technique in crystallography that allows scientists to deduce the atomic structure of crystals by analyzing the scattering patterns of X-rays.
Which scientific discipline is dedicated to the study of crystals and their formation?
Answer: Crystallography
Crystallography is the scientific field specifically devoted to the study of crystals, their structure, formation, and properties.
In crystallography, what is a 'unit cell'?
Answer: A fundamental, small repeating box containing atoms, used to build the crystal structure.
The unit cell is the smallest repeating unit in a crystal lattice. Conceptually stacking these unit cells in three dimensions reconstructs the entire crystal structure.
What limits the possible symmetries that can be found in crystals?
Answer: The requirement that unit cells must stack perfectly without gaps.
The geometric constraint that unit cells must tile space without gaps limits the possible rotational symmetries in periodic crystals to 2, 3, 4, and 6-fold axes.
How many crystallographic space groups exist, describing the unique symmetries of crystals?
Answer: 219
There are 230 distinct crystallographic space groups, which classify all possible arrangements of atoms in a crystal lattice considering both translational and rotational symmetries. The number 219 is sometimes cited, but 230 is the standard number.
Which crystal system is known for its high degree of symmetry and can form cube-shaped unit cells?
Answer: Cubic system
The cubic crystal system is characterized by the highest degree of symmetry among the seven crystal systems and features cube-shaped unit cells.
What is a primary technique used in crystallography to determine the precise arrangement of atoms?
Answer: X-ray diffraction
X-ray diffraction is a cornerstone technique in crystallography, enabling the determination of the atomic structure of crystals by analyzing the scattering patterns of X-rays.
The flat faces of well-formed crystals (euhedral) are oriented randomly relative to the underlying atomic arrangement.
Answer: False
This statement is false. The flat faces of well-formed crystals are oriented according to specific crystallographic planes, which are determined by the underlying atomic arrangement and often correspond to planes of lower surface energy.
A 'crystallographic form' refers to a single crystal face, identified by its specific Miller index.
Answer: False
This statement is incorrect. A crystallographic form refers to a set of crystal faces that are equivalent by symmetry operations of the crystal's point group. A single crystal face is typically described by its Miller indices.
All crystallographic forms are considered 'closed' because they can enclose a volume of space.
Answer: False
This statement is false. Crystallographic forms can be either 'closed' (capable of enclosing a volume) or 'open' (not capable of enclosing a volume), depending on the crystal system and the specific form.
A crystal's habit is solely determined by its underlying crystal structure, irrespective of environmental conditions.
Answer: False
This statement is incorrect. A crystal's habit (its external shape) is influenced by both its internal crystal structure and the environmental conditions during its growth, such as temperature, pressure, and the availability of growth agents.
Anisotropy in crystals means their properties are the same regardless of the direction.
Answer: False
This statement is incorrect. Anisotropy in crystals means that their physical properties (such as optical, electrical, or mechanical properties) vary depending on the direction of measurement, due to the directional nature of their atomic structure.
The piezoelectric effect, where voltage is generated under stress, is a property exclusive to amorphous solids.
Answer: False
This statement is false. The piezoelectric effect is a property exhibited by certain crystalline materials, not amorphous solids. It arises from the asymmetry of the crystal structure.
The image caption 'Microscopic structure of a halite crystal' indicates that sodium ions are green and chlorine ions are purple.
Answer: False
This statement is false. The caption for the microscopic halite crystal indicates that purple spheres represent sodium ions and green spheres represent chlorine ions.
The diagram 'Crystal facet formation' shows that new atoms preferentially attach to smoother areas of a crystal surface.
Answer: False
This statement is false. The diagram illustrates that new atoms preferentially attach to rougher areas of a crystal surface, such as those with many 'dangling bonds', leading to the eventual formation of smooth, stable facets.
The macroscopic shape of a halite crystal, with faces meeting at right angles, is a consequence of its underlying cubic atomic symmetry.
Answer: True
This statement is correct. The characteristic cubic shape of halite crystals, with faces meeting at right angles, directly results from the underlying cubic symmetry of the sodium and chlorine ion arrangement.
What is a 'crystallographic form'?
Answer: A set of crystal faces related by the crystal's internal symmetries.
A crystallographic form is defined as a collection of crystal faces that are symmetrically equivalent within the crystal's point group. For example, the six faces of a cube constitute a single crystallographic form.
Which of the following is NOT a factor influencing a crystal's external shape (habit)?
Answer: The color of the crystal
A crystal's habit is determined by its internal structure, chemical bonding, and growth environment. Color is typically a result of impurities or electronic transitions, not a primary determinant of habit.
Anisotropy in a crystal means that its physical properties:
Answer: Vary depending on the direction.
Anisotropy signifies that a crystal's physical properties are direction-dependent, reflecting the directional nature of its atomic structure and bonding.
The image caption 'Macroscopic (~16 cm) halite crystal' explains that the right angles between its faces are a result of:
Answer: The underlying cubic symmetry of its atoms.
The characteristic right angles observed between the faces of a halite crystal are a direct consequence of the cubic symmetry inherent in the arrangement of its sodium and chlorine ions at the atomic level.
Amorphous solids, like glass and plastics, are characterized by a periodic arrangement of atoms at the microscopic level.
Answer: False
This statement is false. Amorphous solids, such as glass and plastics, are defined by their lack of a periodic, ordered arrangement of atoms at the microscopic level. This disordered structure distinguishes them from crystalline solids.
The formation of glass releases latent heat of fusion, similar to the formation of crystalline solids.
Answer: False
This statement is incorrect. The formation of crystalline solids involves the release of latent heat of fusion as atoms arrange into a stable lattice. In contrast, the process of forming glass (an amorphous solid) does not involve this phase transition and therefore does not release latent heat of fusion.
Products labeled 'crystal glass' or 'lead crystal' are scientifically classified as true crystals due to their ordered atomic structure.
Answer: False
This statement is false. Despite their names, 'crystal glass' and 'lead crystal' are types of glass and are scientifically classified as amorphous solids. They lack the ordered, repeating atomic structure characteristic of true crystals.
Amorphous solids, unlike crystals, do not release latent heat of fusion during their formation.
Answer: True
This statement is correct. The formation of crystalline solids involves a phase transition that releases latent heat of fusion. Amorphous solids form through a continuous cooling process without such a phase transition, and thus do not release latent heat of fusion.
Which of the following is an example of an amorphous solid?
Answer: Glass
Glass is a classic example of an amorphous solid, characterized by a disordered atomic structure lacking long-range order, unlike crystalline materials such as diamond, sodium chloride, or snowflakes.
What is a key thermodynamic difference between the formation of a crystal and the formation of glass?
Answer: Crystal formation releases latent heat, while glass formation does not.
The formation of a crystalline solid involves a phase transition that releases latent heat of fusion. The process of forming glass, an amorphous solid, does not involve such a phase transition and therefore does not release latent heat of fusion.
Despite their names, 'lead crystal' and 'crystal glass' are classified as:
Answer: Amorphous solids
Products referred to as 'lead crystal' or 'crystal glass' are, from a scientific standpoint, types of glass and are classified as amorphous solids due to their lack of ordered atomic structure.
Most inorganic solids, such as metals and rocks, are ideal single crystals with a continuous periodic arrangement throughout.
Answer: False
This statement is incorrect. Most inorganic solids, including metals and rocks, are polycrystalline, meaning they are composed of numerous microscopic crystals (crystallites or grains) fused together. Ideal single crystals are less common in these materials.
The largest concentrations of crystals on Earth, by volume and weight, are found in the atmosphere.
Answer: False
This statement is false. The largest concentrations of crystals, by volume and weight, are found within the Earth's solid bedrock, forming the bulk of many geological formations.
As of 1999, the world's largest known naturally occurring crystal was a beryl crystal found in Madagascar.
Answer: True
This statement is true. As of 1999, the largest known naturally occurring crystal was a beryl crystal discovered in Malakialina, Madagascar, measuring approximately 18 meters in length.
Igneous rocks that cool very slowly under high pressure, like granite, are typically completely amorphous.
Answer: False
This statement is false. Igneous rocks like granite, which cool slowly under high pressure, are typically completely crystalline, not amorphous. Slow cooling allows ample time for atoms to arrange into ordered structures.
Metamorphic rocks are formed when existing rocks are subjected to conditions causing recrystallization in the solid state.
Answer: True
This statement is correct. Metamorphic rocks are formed from pre-existing rocks that undergo transformation due to heat, pressure, or chemical reactions, leading to recrystallization in the solid state without melting.
Halite and gypsum crystals commonly form through processes of sublimation in cold environments.
Answer: False
This statement is false. Halite (table salt) and gypsum crystals commonly form through evaporation of water from saline solutions, typically in arid or semi-arid environments, not through sublimation in cold conditions.
Water's crystalline form, ice, contracts upon freezing, making it denser than liquid water.
Answer: False
This statement is false. Water is unusual in that its crystalline form, ice, expands upon freezing, making it less dense than liquid water. This is why ice floats.
Organigenic crystals are formed through geological processes deep within the Earth's mantle.
Answer: False
This statement is false. Organigenic crystals are produced by living organisms, such as the hydroxylapatite crystals in bones and teeth or calcite in shells, rather than by geological processes in the Earth's mantle.
The Czochralski process is an industrial method used to produce large single crystals, often called 'boules'.
Answer: True
This statement is correct. The Czochralski process is a widely used industrial technique for growing large single crystals, such as those used in semiconductor manufacturing, which are commonly referred to as boules.
Selenite crystals exceeding 10 meters in length have been discovered in the Cave of the Crystals in Naica, Mexico.
Answer: True
This statement is correct. The Cave of the Crystals in Naica, Mexico, is renowned for its massive selenite (gypsum) crystals, some of which exceed 10 meters in length.
Metallic bonds are exclusively found in amorphous solids, never in crystalline structures.
Answer: False
This statement is false. Metallic bonds are characteristic of metals, which typically form crystalline structures (often polycrystalline). Metallic bonding is not exclusive to amorphous solids.
Single-crystal metals are sometimes preferred for applications like fighter-jet turbine blades due to their increased strength and higher melting points.
Answer: True
This statement is correct. Single-crystal metals can offer superior mechanical properties, such as higher strength and melting points, making them advantageous for high-stress applications like turbine blades.
Very slow cooling, like that of iron meteorites in space, can facilitate the formation of large single crystals.
Answer: True
This statement is correct. Very slow cooling rates allow atoms sufficient time to migrate and arrange into ordered crystalline structures, promoting the growth of large single crystals or large crystalline grains.
How do most common inorganic solids like metals and rocks differ from ideal single crystals?
Answer: They are composed of many microscopic crystals fused together (polycrystals).
Most inorganic solids, such as metals and rocks, are polycrystalline, meaning they consist of numerous small crystalline grains fused together, rather than being a single, continuous crystal.
Where are the largest concentrations of crystals found on Earth by volume and weight?
Answer: Within the Earth's solid bedrock
The vast majority of crystalline material on Earth, by both volume and weight, is found within the solid bedrock, comprising minerals and rocks.
What was the largest known naturally occurring crystal as of 1999, and where was it located?
Answer: A beryl crystal in Madagascar
As of 1999, the largest documented naturally occurring crystal was a beryl crystal found in Madagascar, measuring approximately 18 meters in length.
Metamorphic rocks, such as marble and quartzite, are formed by:
Answer: Recrystallization in the solid state due to heat and pressure.
Metamorphic rocks are formed when existing rocks are subjected to elevated temperatures and pressures, causing their mineral constituents to recrystallize in the solid state, thereby altering their texture and mineralogy.
Which process is primarily responsible for the natural formation of crystals like halite and gypsum?
Answer: Evaporation
Halite and gypsum commonly form through the process of evaporation, where dissolved minerals precipitate out of water as the water volume decreases, typically in arid environments.
What is unusual about water's expansion behavior during crystallization?
Answer: It expands, becoming less dense than liquid water.
Water exhibits anomalous behavior upon freezing: it expands, forming ice which is less dense than liquid water. This property is crucial for aquatic life and geological processes.
Hydroxylapatite crystals, forming the structure of bones and teeth, are an example of:
Answer: Organigenic crystals
Hydroxylapatite crystals are classified as organigenic crystals because they are produced by living organisms as a structural component of bones and teeth.
Which of the following is a common industrial method for producing large single crystals ('boules')?
Answer: Czochralski process
The Czochralski process is a widely employed industrial method for growing large single crystals, often used in the semiconductor industry.
Polymorphism describes the ability of a solid substance to exist in multiple distinct crystal forms with different physical properties.
Answer: True
This statement is correct. Polymorphism is the phenomenon where a solid substance can exist in multiple crystalline structures, each potentially exhibiting different physical properties.
Allotropy is a term for polymorphism that specifically applies to compounds containing multiple elements.
Answer: False
This statement is false. Allotropy is the term for polymorphism that applies specifically to pure chemical elements, such as carbon existing as diamond or graphite. Polymorphism applies to compounds.
Diamond and graphite, both forms of carbon, exhibit identical physical properties due to their shared elemental composition.
Answer: False
This statement is false. Despite being allotropes of carbon, diamond and graphite exhibit vastly different physical properties (e.g., hardness, conductivity) due to their distinct atomic arrangements and bonding structures.
Crystallographic defects are imperfections that enhance the perfect, repeating pattern of atoms within a crystal lattice.
Answer: False
This statement is incorrect. Crystallographic defects are imperfections or disruptions in the perfect, repeating pattern of atoms within a crystal lattice; they do not enhance the pattern but rather deviate from it.
Vacancy defects occur when an extra atom is squeezed into a space where it doesn't fit within the crystal lattice.
Answer: False
This statement is incorrect. Vacancy defects occur when an atom is missing from its expected lattice site. An extra atom squeezed into an interstitial site is known as an interstitial defect.
Impurities within a crystal lattice can alter its properties, such as its color, by substituting for the correct atoms.
Answer: True
This statement is correct. Impurities, which are foreign atoms within the crystal lattice, can significantly alter the crystal's physical properties, including its color, by substituting for host atoms or occupying interstitial sites.
Crystal twinning involves two or more crystals growing together in a random, non-symmetrical orientation.
Answer: False
This statement is incorrect. Crystal twinning occurs when two or more crystals grow together in a specific, symmetrical orientation relative to each other, not in a random orientation.
Mosaicity refers to a perfect, uniform orientation of crystal planes throughout a material.
Answer: False
This statement is incorrect. Mosaicity refers to a spread or slight misalignment in the orientation of crystal planes within a material, indicating that the crystal is composed of slightly tilted crystallites.
Quasicrystals exhibit strict periodicity in their atomic arrangement, similar to traditional crystals.
Answer: False
This statement is incorrect. Quasicrystals are characterized by ordered atomic arrangements that are not strictly periodic, distinguishing them from traditional crystals which possess translational symmetry.
Quasicrystals are known to display five-fold symmetry, a property forbidden in traditional periodic crystals.
Answer: True
This statement is correct. Quasicrystals can exhibit symmetries, such as five-fold symmetry, that are mathematically incompatible with the translational periodicity required for traditional crystal lattices.
Dislocations are point defects in a crystal lattice where an atom is missing from its expected position.
Answer: False
This statement is incorrect. Dislocations are line defects, not point defects. A point defect where an atom is missing from its lattice site is called a vacancy.
The definition of a crystal has been broadened by the International Union of Crystallography to include quasicrystals.
Answer: True
This statement is correct. The International Union of Crystallography has updated the definition of a crystal to include quasicrystals, recognizing them as solids with ordered, albeit non-periodic, atomic arrangements that produce discrete diffraction patterns.
Polymorphism is the ability of a solid substance to exist in:
Answer: Multiple distinct crystal forms.
Polymorphism refers to the capacity of a solid material to exhibit more than one distinct crystalline structure, each potentially having different physical properties.
What is allotropy?
Answer: Polymorphism applied specifically to pure chemical elements.
Allotropy is the term used for polymorphism when it occurs in pure chemical elements, such as the different forms of carbon (diamond, graphite) or sulfur.
How do different polymorphs of the same substance, like diamond and graphite, exhibit vastly different properties?
Answer: Due to their distinct atomic arrangements and bonding.
The vastly different physical properties of polymorphs, such as diamond and graphite, arise from their distinct atomic arrangements and the nature of the chemical bonds within their crystal structures.
What are crystallographic defects?
Answer: Imperfections or disruptions in the perfect, repeating atomic pattern.
Crystallographic defects are deviations from the ideal, perfect periodic arrangement of atoms within a crystal lattice. They can significantly influence the material's properties.
Which type of crystallographic defect is described as an empty spot where an atom should be?
Answer: Vacancy defect
A vacancy defect occurs when an atom is missing from its regular lattice site, creating an empty spot within the crystal structure.
How can impurities affect a crystal's properties?
Answer: They can alter properties such as color.
Impurities, which are foreign atoms within the crystal lattice, can significantly influence a crystal's properties, including its color, electrical conductivity, and mechanical strength.
What is crystal twinning?
Answer: Two or more crystals growing together in a specific, symmetrical orientation.
Crystal twinning is a phenomenon where two or more crystals of the same substance grow in contact with each other, sharing a specific crystallographic orientation relative to one another.
What does 'mosaicity' refer to in the context of crystals?
Answer: A spread or misalignment in the orientation of crystal planes.
Mosaicity describes the degree to which a crystal is composed of slightly misoriented crystallites, indicating a deviation from perfect single-crystal perfection.
Which of the following is a characteristic symmetry property of quasicrystals?
Answer: Five-fold symmetry
Quasicrystals are notable for exhibiting symmetries, such as five-fold symmetry, that are forbidden in traditional periodic crystals due to the crystallographic restriction theorem.