Molecules vs Crystal Structures - Middle School Physical Science

What is the definition of an extended structure in a solid (such as a crystal)?

A repeating network of atoms or ions extending throughout the solid. Crystals have no discrete units, just continuous patterns.
What term describes the repeating arrangement of particles in a crystal?

Crystal lattice. This 3D pattern extends infinitely in all directions.
Choose the correct classification for sugar ( $C_{12}H_{22}O_{11}$ ): molecule or extended ionic lattice?

Molecule (a molecular compound). Sugar exists as discrete covalently bonded molecules.
Which model feature best indicates a substance is made of molecules: repeating lattice or separate clusters?

Separate clusters of atoms (discrete units). Molecules form distinct groups that don't connect to neighboring groups.
Identify the correct classification for ice: separate $H_2O$ molecules or an ionic lattice?

Separate $H_2O$ molecules arranged in a crystal by intermolecular forces. Ice contains discrete water molecules held by hydrogen bonds.
Which model feature most strongly indicates a substance is made of molecules: repeating lattice or separate clusters?

Separate clusters (discrete groups) indicate molecules. Molecules exist as individual units, not continuous patterns.
Identify the correct classification for $\text{H}_2\text{O}$ : molecule or extended structure.

Molecule. Water exists as discrete $\text{H}_2\text{O}$ units.
Choose the correct classification: $CO_2$ is best modeled as a molecule or an extended lattice?

Molecule. $CO_2$ forms discrete covalent molecules, not crystals.
Which property is more typical of ionic crystals than molecular substances: low or high melting point?

High melting point. Strong ionic bonds require more energy to break.
What is an extended structure (crystal) in terms of how particles are arranged?

A repeating 3D pattern of particles extending in many directions. Crystals have no discrete boundaries, extending continuously in space.
Choose the word that best completes: A crystal has a repeating ______ pattern.

Three-dimensional. Crystal patterns extend in length, width, and height.
Which category describes $H_2O$ : molecule or extended structure?

Molecule. Water exists as discrete $H_2O$ units with covalent bonds.
What term describes a solid made of ions in a repeating pattern, not separate molecules?

Ionic crystal (ionic lattice). Ions arrange in repeating patterns without forming discrete molecular units.
Identify the structure type for $H_2O$ : molecule or extended crystal lattice?

Molecule. Water exists as discrete $H_2O$ units with two H atoms bonded to one O atom.
What is an extended structure (crystal) in terms of how particles are connected?

A repeating network of atoms or ions extending in all directions. Crystals form continuous 3D networks, unlike isolated molecules.
Which label fits a model of diamond showing each C bonded to 4 others in a continuous network?

Extended structure (covalent network crystal). Each carbon bonds to 4 others in an endless network.
Which type of substance is often represented by a formula unit ratio, such as $NaCl$ , rather than a molecule?

An ionic crystal (extended structure). Ionic formulas show the simplest ratio of ions in the crystal.
Which model feature indicates an ionic crystal rather than a molecular substance?

Alternating ions in a repeating lattice with no separate molecules. Ionic crystals lack discrete molecular units.
Identify the correct label for a model showing alternating $Na^+$ and $Cl^-$ repeating in 3D.

Crystal lattice (extended ionic structure). Alternating ions in 3D indicate an ionic crystal lattice.
Which substance type is usually modeled as a lattice of alternating positive and negative ions?

An ionic crystal. Ionic compounds form extended lattices, not molecules.
Identify the substance type from a model labeled "Na $^+$ " and "Cl $^-$ " repeating with no endpoints.

Extended ionic crystal lattice. No endpoints means the structure continues indefinitely.
Identify the structure type for $NaCl$ : molecule or extended crystal lattice?

Extended crystal lattice. $Na^+$ and $Cl^-$ ions form a continuous 3D lattice, not discrete molecules.
Which model feature most strongly indicates a crystal: separate clusters or a repeating pattern that continues?

A repeating pattern that continues indicates a crystal lattice. Crystals have no boundaries, just endless repetition.
Which option best describes ionic compounds in models: discrete molecules or extended ion lattices?

Extended ion lattices (crystals), not discrete molecules. Ionic compounds form continuous lattices of alternating ions.
Which label fits a model showing metal atoms packed in repeating layers with no separate groups?

Extended structure (metallic crystal lattice). Metal atoms share electrons in continuous lattices.
What is an extended structure (crystal) in terms of particle arrangement?

A repeating 3D lattice of particles with no single, separate unit. Crystals extend infinitely with ordered, repeating arrangements.
What key feature in a model distinguishes a molecule from a crystal lattice?

Molecules are separate units; lattices are continuous repeating networks. Molecules have boundaries; lattices extend infinitely.
Identify the correct classification: a model shows alternating ions in a repeating $+$ and $-$ grid.

Ionic crystal (extended structure). Alternating ions in a continuous grid form crystal lattices.
Which option is a molecule: $CO_2$ or a diamond crystal lattice?

$CO_2$ . Carbon dioxide exists as discrete molecular units.
Identify the substance type from a model of many separate " $\text{CO}_2$ " groups spaced apart.

Molecular substance (discrete molecules). Separate groups indicate individual molecular units.
Which type of structure is typically represented by many connected spheres with no clear endpoints?

An extended structure (crystal or network). No endpoints indicate continuous crystal networks.
Identify the correct label for a model showing only one cluster like $H_2O$ repeated as separate clusters.

Molecular substance (made of molecules). Water exists as separate $H_2O$ units, not continuous networks.
Which property is more typical of many molecular substances than ionic crystals: low or high melting point?

Low melting point. Weak intermolecular forces make molecules easier to melt.
Identify the correct classification for $\text{SiO}_2$ in quartz: molecule or extended structure.

Extended structure (network crystal). Quartz has a continuous network of Si-O bonds.
Which option describes an extended structure: discrete molecules or repeating network with no single molecule?

Repeating network with no single molecule. Extended structures lack discrete molecular boundaries.
Which classification fits graphite: discrete molecules or an extended layered network?

Extended layered covalent network (crystal structure). Carbon atoms form covalent sheets stacked by weak forces.
Identify the structure type: a model shows alternating $+$ and $-$ ions repeating in a 3D grid.

Extended crystal structure (ionic crystal lattice). Alternating charges in 3D indicate an ionic crystal lattice.
Identify the correct classification: a model shows many identical $H_2O$ groups spaced apart.

Molecular substance. Separate $H_2O$ units indicate individual molecules.
What is the correct classification for a solid made of repeating identical molecules held by attractions?

Molecular solid (made of molecules, not an atomic lattice). Contains discrete molecules held by intermolecular forces.
Which option best matches "lattice points": atoms in one molecule or repeating particle positions?

Repeating particle positions. Lattice points mark where particles repeat in crystals.
Which type of structure is typical for covalent compounds such as water, $H_2O$ ?

Molecules. Covalent compounds form discrete, countable molecular units.
What is the definition of an extended structure such as a crystal?

A repeating lattice of atoms, ions, or molecules extending in 3D. Crystals have no discrete boundaries, extending indefinitely.
What is the definition of a molecule in terms of atoms and bonds?

A discrete group of atoms held together by chemical bonds. Molecules exist as individual units with defined boundaries.
What is the definition of an extended structure (crystal) in particle models?

A repeating 3D arrangement of particles with no single unit molecule. Crystals extend infinitely without discrete molecular boundaries.
Which category describes table salt ( $NaCl$ ) in a solid: molecule or crystal lattice?

Crystal lattice (extended ionic structure). Solid salt forms continuous $Na^+$ and $Cl^-$ ionic lattice.
Which type of model usually shows a molecule: ball-and-stick or lattice array?

Ball-and-stick model. Ball-and-stick models show individual atoms and bonds in discrete molecules.
Which option is an extended structure: sugar molecules or quartz ( $SiO_2$ ) crystal network?

Quartz ( $SiO_2$ ) crystal network. Quartz forms a continuous covalent network, not molecules.
What does it mean if a model shows separate clusters with clear boundaries between them?

It represents molecules as discrete particles. Each cluster is a complete, independent molecule.
Which option best indicates a model represents a molecule: repeating lattice or a single bonded cluster?

A single bonded cluster (one discrete unit). Molecules exist as individual, separate units.
Which classification fits a model with identical pairs of atoms (diatomic units) repeated but not connected?

Molecular substance (diatomic molecules). Paired atoms forming separate units are still molecules.
Identify the structure from a model showing alternating $+$ and $-$ ions in a repeating grid pattern.

Ionic crystal (extended lattice). Alternating charges in a grid show continuous ionic bonding.
What is the key visual clue in a particle diagram that indicates an extended structure?

A repeating pattern that continues beyond the drawn region. Extended structures show patterns that continue indefinitely in all directions.
Which model feature best indicates a crystal: separate units or a continuous repeating pattern?

A continuous repeating pattern (lattice). Crystals lack discrete boundaries, forming continuous 3D networks.
Which model feature best indicates a substance is made of molecules: repeating lattice or separate groups?

Separate groups of atoms (distinct units). Molecules don't form continuous lattices; they remain as individual units.
Which option best describes quartz, $SiO_2$ , in a solid model: molecule or extended structure?

Extended structure. Silicon and oxygen form continuous covalent networks.
Which option is an example of an ionic crystal: $NaCl$ or $CH_4$ ?

$NaCl$ . $NaCl$ forms a continuous lattice of $Na^+$ and $Cl^-$ ions.
Which option best indicates a network covalent crystal model: separate molecules or one continuous bonded network?

One continuous bonded network indicates a network covalent crystal. All atoms bond to neighbors in an endless 3D network.
Which model feature best indicates a crystal: separate clusters or a continuous repeating pattern?

A continuous repeating pattern (lattice). Crystals have particles bonded in all directions without endpoints.
Which type of substance is made of discrete covalent units: molecular compound or ionic crystal?

Molecular compound. Covalent bonds form separate molecules, not continuous networks.
What is an extended structure (crystal) in terms of repeating particles?

A repeating 3D pattern of particles extending throughout a solid. Crystals have no discrete units, just continuous patterns.
What is a formula unit?

The lowest whole-number ratio of ions in an ionic compound. Formula units express the simplest ion ratio in crystals.
What does it mean if a ball-and-stick model shows the same pattern repeating beyond the edges?

It represents an extended structure (a crystal lattice). Pattern continuation indicates no discrete molecular boundaries.
Which option is a molecular element: $O_2$ or iron ( $Fe$ ) crystal?

$O_2$ . $O_2$ exists as diatomic molecules, not a continuous lattice.
What is a molecule in terms of how many atoms it contains and how they are connected?

A discrete group of atoms held together by chemical bonds. Molecules have definite boundaries, unlike extended structures.
Which option best indicates a crystal rather than a molecule: discrete unit or repeating lattice?

Repeating lattice. Crystals repeat endlessly; molecules are individual units.
Which category best fits $NaCl$ in a particle model: molecule or extended crystal structure?

Extended crystal structure (ionic crystal lattice). Salt forms a continuous lattice of alternating Na+ and Cl- ions.
Which option best indicates a molecule rather than a crystal: fixed number of atoms or repeating pattern?

Fixed number of atoms. Molecules have definite formulas; crystals extend indefinitely.
Which type of structure is typical for ionic compounds such as sodium chloride?

Extended crystal lattice. Ionic compounds form continuous 3D networks, not discrete units.
Which option is molecular: methane $CH_4$ or sodium chloride $NaCl$ lattice?

$CH_4$ is molecular. $CH_4$ forms discrete molecules; $NaCl$ forms continuous lattices.
Which key feature distinguishes a molecule from a crystal lattice in a model?

Molecules are separate units; lattices repeat with no single unit. Molecules have boundaries; crystals are continuous networks.
Which category best fits $CO_2$ in a particle model: molecule or extended crystal structure?

Molecule. Carbon dioxide exists as separate $CO_2$ units.
What is the key structural difference between a molecular substance and a crystal lattice?

Molecules are discrete units; lattices are continuous repeating networks. Molecules have boundaries; crystals extend infinitely.
Identify the correct label for a repeating NaCl model: "NaCl molecule" or "NaCl formula unit in a lattice"?

"NaCl formula unit in a lattice.". NaCl exists as a lattice, not individual molecules.
What does it mean if a model shows a single cluster that can be separated from others without breaking bonds?

It represents a molecule (a discrete particle). Discrete units can exist independently without breaking covalent bonds.
Which option best describes why an ionic compound is not usually a molecule?

It is a lattice of ions, not separate bonded groups. Ionic compounds form continuous lattices, not discrete units.
Identify the structure type: a model shows many identical triatomic groups separated from each other.

Molecular substance (discrete molecules). Separated groups indicate individual molecules, not a lattice.
What is the correct term for a crystal made of positive and negative ions in a repeating pattern?

Ionic crystal lattice. Oppositely charged ions arrange in repeating 3D patterns.
What is the key difference between a molecular formula and a crystal formula unit?

Molecules are discrete; formula units represent a repeating ratio in a lattice. Molecules show actual atoms; formula units show simplest ratio.
What term describes the smallest repeating unit in a crystal lattice model?

Unit cell. The unit cell repeats to build the entire crystal structure.
What does it mean if a model shows a pattern that could be extended in all directions without changing?

It represents an extended structure (a crystal lattice). The pattern has no edges or discrete units.
Identify the term for the smallest repeating unit in a crystal structure model.

Unit cell. The basic repeating pattern that builds the entire crystal.
Which type of bonding usually forms discrete molecules: ionic or covalent?

Covalent bonding. Covalent bonds create discrete molecular units with shared electrons.
Which option best describes a formula unit such as NaCl: molecule or repeating ionic ratio in a lattice?

A repeating ionic ratio in a lattice (not a molecule). NaCl has no discrete units, just repeating ion pairs.
Which option best describes a molecular model: one continuous network or separate identical units?

Separate identical units (individual molecules). Molecules maintain their identity as separate entities.
What is a molecule in terms of atoms and bonding?

A discrete group of atoms held together by covalent bonds. Molecules form when atoms share electrons through covalent bonds.
Identify the structure type for diamond: discrete molecules or extended network crystal?

Extended network crystal (covalent network). Carbon atoms form a continuous covalent network.
What is an extended structure in a particle model (such as a crystal)?

A repeating network of particles bonded in a continuous pattern. Unlike molecules, extended structures have no discrete boundaries.
Which classification fits a model showing a 3D repeating array of spheres with no separated groups?

Extended structure (crystal lattice). 3D arrays without gaps indicate continuous crystal structures.
Which model feature most strongly indicates a substance is made of molecules?

Separate, repeating clusters with clear boundaries between groups. Molecules exist as individual units, not continuous networks.
What is a molecule in terms of how many atoms are connected as a single unit?

A discrete group of atoms bonded together as one unit. Molecules exist as individual, complete units with defined boundaries.
What term describes the smallest repeating unit of a crystal lattice model?

Unit cell. The basic building block that repeats to form the entire crystal.
Identify the model that represents molecules: A) repeating pairs separated, B) infinite grid connected.

A) repeating pairs separated. Separated pairs indicate discrete molecular units.
Identify the structure type for sugar (sucrose): discrete molecules or an ionic lattice?

Discrete molecules (a molecular substance). Sugar molecules remain intact as separate units.
Identify the correct classification for $\text{NaCl}$ (table salt): molecule or crystal lattice.

Crystal lattice (extended ionic structure). Salt forms continuous ionic lattices, not molecules.
Which category best fits $H_2O$ in a particle model: molecule or extended crystal structure?

Molecule. Water exists as individual $H_2O$ units, not a continuous lattice.
What is a molecule in a particle model (in terms of atoms and bonding)?

A discrete group of atoms held together by chemical bonds. Molecules are separate units, not continuous like crystals.
What is the definition of an extended structure (crystal) in particle-model terms?

A repeating network of particles extending in all directions. Crystals have no discrete boundaries, forming continuous 3D patterns.
Which option is a molecule: diamond ( $C$ ) or methane ( $CH_4$ )?

Methane ( $CH_4$ ). Methane exists as discrete units with one C atom bonded to four H atoms.
What does the formula $CO_2$ represent: a ratio in a lattice or a discrete particle?

A discrete particle (a molecule). Each $CO_2$ exists as an individual, complete molecule.
What key model clue shows a substance is not made of molecules: no separate units or repeated units?

No separate units; particles connect in a continuous repeating network. Continuous networks lack the discrete boundaries of molecules.
Which label best fits a model showing repeating spheres with no distinct groups, typical of a metal?

Extended structure (metallic crystal). Metals form lattices with delocalized electrons, no distinct groups.
What is the key visual clue in a particle diagram that indicates a molecule?

A limited, countable group of atoms forming one unit. Molecules appear as complete, isolated clusters with clear boundaries.
Which option best describes a molecule model: discrete unit or repeating pattern?

Discrete unit. Molecules exist as individual, countable particles.
What is the definition of a molecule in terms of atoms and bonding?

A discrete group of atoms held together by chemical bonds. Molecules have defined boundaries, unlike continuous crystal networks.
Identify the classification for a model of $H_2$ shown as many separate pairs spread out.

Molecules (diatomic molecular substance). Each $H_2$ pair is a complete, separate molecule.
Which model feature most strongly indicates a crystal: separate groups or a continuous repeating lattice?

A continuous repeating lattice (an extended structure). Crystals have atoms/ions bonded continuously throughout the structure.
Which type of bonding most commonly forms an ionic crystal lattice: covalent, ionic, or metallic?

Ionic bonding forms an ionic crystal lattice. Oppositely charged ions attract in all directions.
Which type of bonding most directly forms individual molecules?

Covalent bonding. Shared electrons in covalent bonds create discrete molecules.
What is the smallest particle that still has the properties of a molecular substance?

A molecule. Molecules retain substance properties as independent units.
Identify the classification: a model shows atoms connected in a continuous hexagonal sheet (graphite-like).

Extended structure (covalent network). Continuous hexagonal bonding indicates covalent network structure.
Identify the substance type from a formula model: $H_2O$ represents what kind of structure?

Molecules (discrete units). $H_2O$ forms individual molecules with 3 atoms each.
Which statement correctly compares a molecular model and a crystal lattice model?

Molecular: separate bonded groups; crystal: repeating pattern of particles. Key difference is discrete units vs. continuous patterns.
What does the term lattice mean in particle models of crystals?

A regular repeating arrangement of particles in space. Lattices are ordered 3D patterns of particles.
Which choice best describes metallic solids in models: discrete molecules or a lattice of metal atoms with delocalized electrons?

A lattice of metal atoms with delocalized electrons. Metal atoms share electrons throughout the structure.
Which statement matches a molecular solid model: "repeating lattice" or "individual molecules packed"?

Individual molecules packed. Molecular solids contain distinct molecules, not continuous lattices.
What term names the smallest repeating pattern in a crystal lattice model?

Unit cell. The unit cell repeats to build the entire crystal structure.
What is the definition of an extended structure (crystal) in terms of repeating units?

A repeating 3D lattice of atoms, ions, or molecules with no discrete unit. Crystals extend infinitely without distinct molecular boundaries.
What is a formula unit, and which type of structure does it usually describe?

Lowest whole-number ion ratio; usually an extended ionic lattice. Formula units show ion ratios in continuous crystals.
Which category best fits diamond or quartz: molecular substance or extended covalent network crystal?

Extended covalent network crystal. These form continuous 3D networks of covalent bonds.
Identify whether this model description is a molecule or crystal: "a single unit can be circled."

Molecule. Discrete, circled units indicate individual molecules.
Which option best describes carbon dioxide, $CO_2$ , in a particle model: molecule or extended structure?

Molecule. $CO_2$ forms individual units, not continuous networks.
Identify the key bonding difference: molecules versus extended structures in particle models.

Molecules have bonds within a group; crystals have bonds throughout a lattice. Molecular bonds connect limited atoms; crystal bonds extend infinitely.
What is the key difference between a molecular formula and a lattice formula unit?

Molecule is discrete; formula unit is the simplest ion ratio in a lattice. Molecules exist independently; formula units only represent ratios.
What is a molecule in terms of how many atoms are bonded together?

A discrete group of $2$ or more atoms bonded together. Molecules are distinct units, not single atoms or continuous networks.
What is the smallest repeating unit in a crystal lattice called?

Unit cell. This basic building block repeats to form the entire crystal structure.
Identify the classification: a model shows separated identical groups shaped like $H_2O$ units.

Molecules (a molecular substance). Separate $H_2O$ groups indicate molecular structure, not extended.
What is the smallest repeating unit of a crystal lattice called?

Unit cell. This basic building block repeats to form the entire crystal.
Which option indicates a molecule model: a fixed number of atoms per unit or an indefinite repeating grid?

A fixed number of atoms per unit. Molecules have a specific, countable number of atoms in each unit.
Which statement best distinguishes a molecule from a crystal: discrete unit or repeating lattice?

Molecule: discrete unit; crystal: repeating lattice. Key difference: molecules are isolated units, crystals are continuous patterns.
Which label best fits a model that extends in all directions with repeated bonds and no separate units: molecule or crystal?

Crystal (extended structure). No separate units indicates an extended crystal structure.
Which category best fits diamond (carbon) in a particle model: molecule or extended crystal structure?

Extended crystal structure (covalent network crystal). Each carbon bonds to 4 others in a continuous 3D network.
What is a molecule in terms of atoms and bonding?

A discrete group of atoms held together by chemical bonds. Molecules have defined boundaries, unlike extended structures.
What is the smallest unit that still represents a molecular substance?

One molecule. Molecules are the smallest complete units of molecular compounds.
What is a covalent network solid in terms of particle arrangement?

Atoms bonded in a continuous 3D network (an extended structure). All atoms connect through covalent bonds continuously.
Identify the classification: a model shows many $Na^+$ and $Cl^-$ ions in a repeating pattern.

Extended structure (ionic crystal). Alternating ions in a pattern indicate an ionic crystal structure.
Identify the structure type: $NaCl$ in solid form is best modeled as what?

An ionic crystal lattice (extended structure). $Na^+$ and $Cl^-$ ions form a continuous 3D lattice.
What is the key difference between an ionic crystal model and a molecular model?

Ionic crystal: alternating ions in a lattice; molecular: separate molecules. Ionic crystals have continuous lattices; molecular substances have distinct units.
Identify whether $SiO_2$ (quartz) is best modeled as molecules or an extended crystal structure.

Extended crystal structure (covalent network). Silicon and oxygen form a continuous network structure.
Which category describes diamond (carbon): molecule or extended structure?

Extended structure (covalent network crystal). Diamond's carbon atoms form continuous 3D covalent network.
Which option best describes a crystal lattice model: discrete unit or repeating pattern?

Repeating pattern. Crystal structures repeat the same arrangement throughout.
Which type of solid is represented by a model of identical atoms in a repeating close-packed arrangement?

Metallic crystal (metallic lattice). Metal atoms share electrons in a "sea" throughout the lattice.
Identify whether H2O is typically represented as a molecule or as a crystal lattice in a model.

Molecule. Water forms discrete H₂O units with covalent bonds.
What does it mean if a model shows a pattern repeating in all directions?

It represents an extended structure (a crystal lattice). Crystals extend infinitely through repeating patterns.
Which type of bonding usually forms extended crystal lattices: ionic or covalent?

Ionic bonding. Ionic attractions extend in all directions, forming lattices.
Which option best describes sodium chloride, $NaCl$ , in a solid model: molecule or extended structure?

Extended structure. Salt forms ionic crystals, not separate $NaCl$ molecules.
What term describes a substance made of separate, individual groups of bonded atoms?

Molecular substance (made of discrete molecules). Molecules exist as separate, independent units of bonded atoms.
Which model feature most strongly indicates an extended crystal structure?

A continuous repeating lattice with no separate units. Crystals form continuous 3D networks without discrete molecules.
Which choice best matches: molecules have a chemical formula as one unit, crystals have a formula unit repeated?

Crystals repeat formula units; molecules exist as single units. Formula units repeat in crystals; molecules exist as complete formula units.
Which option indicates an extended structure: "many ions repeating" or "one bonded group"?

Many ions repeating. Extended structures have continuous, repeating arrangements.
Identify the key visual clue in a model that indicates a crystal lattice.

A repeating, regular pattern extending in all directions. Crystal models show ordered patterns extending infinitely.
Which model feature shows a molecule: a boundary around one unit or no clear boundary?

A boundary around one unit. Boundaries indicate discrete molecules, not continuous structures.
What term describes a solid made of a repeating pattern of particles throughout the solid?

Crystal (extended structure with a repeating lattice). Crystals have particles arranged in regular, repeating 3D patterns.
Identify the structure type: a model shows a continuous hexagonal sheet of atoms bonded throughout.

Extended crystal structure (covalent network, like graphite layers). Continuous bonding throughout indicates a network crystal.
Which statement is correct: crystals have a fixed lattice ratio, or crystals exist as single separate units?

Crystals have a fixed lattice ratio in a repeating pattern. Crystal ratios repeat throughout the lattice, unlike molecules.
What general property is most associated with ionic crystals: low melting point or high melting point?

High melting point. Strong ionic bonds require high energy to break.
Which option best describes the formula $NaCl$ in a crystal: exact particle count or ratio?

Ratio of ions in the lattice, not a count in one molecule. Formula shows simplest ion ratio in the infinite lattice.
Choose the correct statement: In a crystal model, does the pattern repeat in $3$ dimensions or stay as one unit?

The pattern repeats in $3$ dimensions. Crystal patterns extend in length, width, and height directions.
Which option best describes a crystal model: particles arranged randomly or in a repeating pattern?

Particles arranged in a repeating pattern. Crystal structures have ordered, predictable arrangements.
What term describes the smallest repeating pattern in a crystal lattice model?

Unit cell. The unit cell is the basic building block that repeats to form the entire crystal.
What term describes the smallest repeating unit that builds a crystal lattice?

Unit cell. This basic building block repeats to form the entire crystal.
What type of attraction usually holds ions together in an ionic crystal lattice?

Electrostatic attraction between oppositely charged ions. Positive and negative charges attract throughout the crystal.
Identify the model type: separate clusters of atoms with space between clusters in the solid.

Molecular substance (discrete molecules). Separate clusters indicate individual molecules, not a lattice.
Identify the correct classification for $\text{CO}_2$ : molecule or extended structure.

Molecule. Carbon dioxide forms individual $\text{CO}_2$ units.
Identify the correct label for a model showing many separate $H_2O$ groups not connected to each other.

Molecules (discrete particles). Separate water groups show individual molecules.
Which statement matches an ionic crystal model: "individual molecules" or "ions in a repeating pattern"?

Ions in a repeating pattern. Ionic crystals form continuous lattices, not separate molecules.
Which option best describes covalent compounds like $H_2O$ : discrete molecules or ion lattices?

Discrete molecules. Covalent compounds form individual molecular units with defined formulas.
Which option is an example of a molecular substance: $CO_2$ or $NaCl$ ?

$CO_2$ . $CO_2$ exists as individual triatomic molecules.
Choose the correct classification: a model shows $CO_2$ units separated from each other in a box.

Molecular substance (discrete $CO_2$ molecules). Separated units indicate discrete molecules, not a lattice.
Identify the structure type for sodium chloride, $NaCl$ : molecule or extended crystal lattice?

Extended crystal lattice (ionic crystal), not molecules. $Na^+$ and $Cl^-$ ions form a continuous lattice.
What is an extended structure in a model of matter?

A repeating network of atoms or ions with no single smallest unit. Unlike molecules, extended structures continue indefinitely.
What does a formula like $NaCl$ represent for an ionic crystal?

The simplest whole-number ratio of ions (a formula unit). Ionic formulas show ratios, not actual particle counts.
Which option best describes covalent network solids such as diamond: molecules or extended structures?

Extended structures (covalent network crystals). Each atom bonds to neighbors in an endless network.
What does a chemical formula represent for a molecular compound such as $CO_2$ ?

The actual number of each atom in one molecule. Molecular formulas show exact atom counts per molecule.
Which observation best supports that a model is a crystal: identical repeating pattern or varied cluster shapes?

Identical repeating pattern. Crystals show regular, repeating 3D patterns throughout.
Identify the structure type for water, $H_2O$ : molecule or extended crystal lattice?

Molecule. Water exists as discrete $H_2O$ units.
What is the definition of a molecule in physical science models?

A discrete group of atoms bonded together as one unit. Molecules exist as individual, complete units with defined boundaries.
Which structure is shown by a model where each atom bonds to several neighbors in a continuous mesh?

Extended structure (network solid or lattice). Continuous bonding indicates a network solid.
What term describes a crystal made of atoms bonded in a continuous network (for example, quartz)?

Covalent network crystal. All atoms are covalently bonded in a continuous 3D network without boundaries.
Which property is more typical of ionic crystals than molecular substances: low or high melting point?

High melting point. Strong ionic forces throughout crystals resist melting.
What does it mean if a model shows a fixed number of atoms bonded with a clear boundary around each unit?

It represents molecules (discrete units). Clear boundaries indicate separate molecular units.
What general property is most associated with many molecular substances: low melting point or very high melting point?

Lower melting point (compared with ionic crystals). Weaker intermolecular forces mean easier melting.
Which option best describes water, $H_2O$ , in a particle model: molecule or extended structure?

Molecule. Water exists as discrete $H_2O$ units with clear boundaries.
Which option best indicates a molecular solid model: low-mass particles in a net or separate molecules packed together?

Separate molecules packed together indicate a molecular solid. Individual molecular units retain their identity in solids.
What does the formula $NaCl$ represent in an ionic crystal: one molecule or a ratio in a lattice?

A ratio of ions in a lattice (a formula unit), not a molecule. No individual $NaCl$ molecules exist; ions form continuous lattices.
What is the smallest repeating unit in a crystal lattice model called?

A unit cell. Unit cells repeat to build the entire crystal structure.
Identify the correct statement: In a crystal, particles repeat; in a molecule, atoms repeat without end.

Corrected: In a molecule, atoms form one unit; in a crystal, units repeat. Molecules are single units; crystals are repeating patterns.
What is the key model feature of a metallic crystal?

Metal atoms in a lattice with delocalized electrons. Electrons move freely throughout the metal lattice.
Identify the key visual clue in a model that indicates a molecule.

A single, separate cluster with a definite number of atoms. Molecular models show complete, bounded groups of atoms.
What is the definition of an extended structure (crystal) at the particle level?

A repeating 3D arrangement of particles with no separate units. Crystals extend infinitely in all directions without distinct boundaries.
Which type of model usually shows a crystal: ball-and-stick cluster or repeating lattice array?

Repeating lattice array. Lattice arrays show the continuous, repeating pattern of crystal structures.
Which model feature most strongly indicates a crystal: separate clusters or repeating pattern?

A repeating pattern (lattice) indicates a crystal (extended structure). Crystals show ordered, continuous patterns without gaps.
What is the smallest unit that still represents a crystal such as sodium chloride?

A unit cell (repeating pattern), not a single molecule. Crystals repeat unit cells, not individual molecules.
Which option is typically an ionic crystal: carbon dioxide ( $\text{CO}_2$ ) or sodium chloride (NaCl)?

Sodium chloride (NaCl) is an ionic crystal. NaCl forms a continuous lattice of alternating ions.
Which option best describes bonding in a crystal lattice model: only within units or throughout the repeating structure?

Bonding/attraction throughout the repeating structure. Each particle bonds to neighbors in an endless network.
Identify the correct description for crystals: definite shape from repeating structure or random arrangement?

Definite shape from a repeating internal structure. The regular internal arrangement creates the characteristic crystal shapes.
What term describes the smallest particle unit shown for a molecular substance model?

Molecule. Each complete molecule is the fundamental unit of the substance.
Which option is an extended structure: $O_2$ or $SiO_2$ (quartz) crystal network?

$SiO_2$ (quartz) is an extended crystal network. Quartz forms continuous networks, while $O_2$ exists as molecules.
Identify the model type: a continuous grid of alternating particles extending in all directions.

Crystal lattice (extended structure). Continuous grids show extended structures without boundaries.
What is the key difference between a covalent network crystal and a molecular substance?

Network: atoms bonded in a continuous lattice; molecular: discrete molecules. Networks form continuous structures; molecular substances have separate units.
Which type of bonding most commonly forms discrete molecules: covalent, ionic, or metallic?

Covalent bonding most commonly forms discrete molecules. Atoms share electrons to form distinct molecular units.
What is the key difference in counting particles: molecules have a set formula unit, crystals have what?

No single finite unit; the pattern repeats throughout the solid. Crystals extend infinitely without countable molecular units.
Which type of bonding most often forms an ionic crystal: covalent or ionic?

Ionic bonding. Oppositely charged ions attract in all directions forming lattices.
What is the meaning of "formula unit" in models of ionic crystals such as $NaCl$ ?

Lowest whole-number ratio of ions in the crystal lattice. Shows the simplest ratio of ions, not an actual molecule.
Which feature best indicates a model represents a crystal: a separate unit or a repeating lattice?

A repeating lattice pattern that continues in all directions. Crystals show periodic arrangement extending infinitely.
Identify the correct label for a model showing alternating ions in a repeating grid like $NaCl$ .

Crystal (ionic extended structure). Ionic compounds form continuous 3D lattices, not molecules.
Identify whether NaCl is typically represented as molecules or as an extended ionic crystal lattice.

Extended ionic crystal lattice. Salt forms continuous ionic networks, not molecules.
Which category best fits quartz ( $SiO_2$ ) in a particle model: molecule or extended crystal structure?

Extended crystal structure (covalent network crystal). Silicon and oxygen form a continuous network structure.
What is the definition of a molecule in particle-model terms?

A discrete group of atoms bonded together as one unit. Molecules exist as individual, complete units with defined boundaries.
Which option best indicates a model represents a crystal: identical units repeat in all directions or one unit stands alone?

Identical units repeat in all directions. Crystals show repetition; molecules are standalone units.
Which type of structure is shown by a model with identical units repeating in rows and columns?

An extended structure (crystal lattice). Regular repetition indicates a crystal's continuous structure.
What is the definition of a molecule in terms of atoms and bonding?

A discrete group of atoms held together by chemical bonds. Molecules exist as individual, complete units with defined boundaries.
What is the definition of a molecule in terms of atoms and bonding?

A neutral group of atoms held together by covalent bonds. Covalent bonds create distinct molecular units, not continuous networks.
What does a chemical formula like $H_2O$ represent for a molecular substance?

The actual atoms in one molecule (a discrete particle). Molecular formulas show exact atom counts in each molecule.
What does it mean if a model shows bonds continuing beyond the edges of the picture in all directions?

It represents an extended structure (crystal/network). No discrete boundaries indicate a continuous crystal lattice.
What does the word "lattice" mean in a particle model of a solid?

A regular, repeating arrangement of particles throughout the solid. Particles form an ordered, 3D repeating framework.
What is a formula unit in an ionic crystal such as sodium chloride?

The lowest whole-number ratio of ions, such as $1:1$ for NaCl. Formula units show the simplest ratio, not actual molecular groups.
Which type of structure is typically represented by a ball-and-stick model showing one complete unit only?

A molecule. Ball-and-stick models often show complete molecular units.
Identify the type of bonding most associated with ionic crystals such as sodium chloride.

Ionic bonding in a lattice of ions. Ionic crystals form when oppositely charged ions attract in all directions.
Which classification matches a model of alternating $+$ and $-$ particles repeating in all directions?

Extended ionic crystal lattice. Alternating charges form continuous ionic crystal lattices.
What type of bonding usually holds atoms together within a molecule?

Covalent bonding. Atoms share electrons to form strong bonds within molecules.
Which option is an extended covalent network crystal: diamond ( $C$ ) or methane ( $CH_4$ )?

Diamond ( $C$ ). Diamond has carbon atoms bonded continuously in a 3D network structure.
Identify the model that represents a crystal lattice: A) separated clusters, B) repeating connected array.

B) repeating connected array. Connected arrays show continuous crystal structures.
Which model feature shows an extended structure: identical units repeat without end or one isolated unit?

Identical units repeat without end. Extended structures continue infinitely without discrete boundaries.
What is the correct term for a crystal made of atoms bonded in one continuous covalent network?

Covalent network solid. All atoms share electrons in one giant covalent structure.
Which property is more typical of many molecular substances: low or high melting point?

Low melting point. Weak intermolecular forces allow easier melting.
Which statement is true for crystals: fixed repeating pattern or random arrangement?

Crystals have a fixed repeating pattern (ordered lattice). Crystal structure requires long-range periodic order.
Which option best describes $NaCl$ : $NaCl$ molecules or a $Na^+$ / $Cl^-$ lattice?

A $Na^+$ / $Cl^-$ lattice (not $NaCl$ molecules). No discrete $NaCl$ molecules exist; ions form continuous lattice.
Choose the correct classification: A model shows repeating + and − ions; is it molecular or an extended crystal?

Extended crystal (ionic lattice). Alternating charges create an ionic lattice structure.
Choose the correct classification: A model shows separate identical clusters of atoms; is it molecular or an extended crystal?

Molecular (made of discrete molecules). Distinct clusters indicate separate molecular units.
Which option is an extended covalent network solid: diamond ( $C$ ) or water ( $H_2O$ )?

Diamond ( $C$ ). Diamond has all carbon atoms covalently bonded in one network.
What is the defining feature of a molecule model compared with a crystal model?

Molecule: discrete unit; crystal: repeating lattice extending in 3D. Molecules are individual units; crystals have infinite repeating patterns.
Which category best fits $O_2$ in a particle model: molecule or extended crystal structure?

Molecule. Oxygen gas consists of individual $O_2$ molecules.
Choose the correct classification: $MgO$ is best modeled as a molecule or an extended lattice?

Extended lattice (ionic crystal). $MgO$ forms ionic crystals with continuous lattices.
Which option best describes bonding in a molecular model: bonds within units or bonds throughout a whole lattice?

Bonds within units (within each molecule). Atoms bond to form complete molecules, separate from other molecules.
Which option best describes ionic solids such as sodium chloride: molecules or extended structures?

Extended structures (ionic crystal lattices). Ions form continuous 3D networks, not discrete molecules.
What is a unit cell in a crystal model?

Smallest repeating arrangement that builds the entire crystal. The unit cell repeats to form the entire crystal structure.
Which type of bonding most directly forms extended crystal lattices in basic models?

Ionic bonding. Ionic attractions create continuous 3D crystal networks.
Which option best describes a unit cell in a crystal model?

The smallest repeating block that builds the entire crystal. Unit cells repeat to form the entire crystal structure.
Which category describes $CO_2$ : molecule or extended structure?

Molecule. Carbon dioxide exists as individual $CO_2$ units.
What term describes the smallest repeating unit of a crystal lattice in a model?

Unit cell. The unit cell repeats to build the entire crystal structure.
Which type of substance is typically represented by a chemical formula with a fixed count, such as $H_2O$ ?

A molecular substance. Molecular formulas show exact atom counts in each discrete unit.
Which option describes a molecular substance: definite formula unit or variable-size network?

Definite formula and discrete molecules. Molecules have specific formulas representing complete units.
Identify the structure from a model showing identical groups of $3$ atoms repeated but not connected to each other.

Molecular substance (separate molecules). Groups not connected indicate individual molecules.
Identify the structure type for $CO_2$ : molecule or extended crystal lattice?

Molecule. Carbon dioxide exists as individual units of one C atom bonded to two O atoms.
What property is most associated with ionic crystal lattices: low or high melting point?

High melting point. Strong ionic attractions require high energy to break apart.
Which feature best indicates a model represents a molecule: repeating pattern or a single unit?

A single discrete unit (not a repeating pattern). Molecules have defined edges; crystals repeat endlessly.
Identify the classification for a model of graphite showing hexagon layers that repeat across the page.

Extended structure (covalent network crystal). Graphite's continuous hexagonal sheets form a network solid.
Which option is typically a molecular substance: water ( $\text{H}_2\text{O}$ ) or sodium chloride (NaCl)?

Water ( $\text{H}_2\text{O}$ ) is molecular. Water molecules exist as discrete $\text{H}_2\text{O}$ units.
Which model feature most strongly indicates a substance is made of molecules: repeating pattern or separate groups?

Separate, repeated groups that are not all bonded into one network. Molecules exist as distinct units, not bonded into one continuous network.
Which type of structure is shown by a model with separate, identical clusters spaced apart?

Molecules (discrete particles). Separated clusters indicate individual molecular units.
Which type of bonding forms a covalent network crystal such as quartz ( $SiO_2$ ): discrete or network?

Network covalent bonding (extended structure). Atoms share electrons continuously throughout the structure.
Which option best describes a crystal in a particle model: discrete units or repeating pattern?

Repeating pattern (a lattice) extending in all directions. Crystals have ordered, infinite repetition of structural units.
Identify the structure type for diamond: discrete molecules or an extended network crystal?

Extended network crystal (network covalent). Each carbon bonds to 4 others in a continuous lattice.
Identify the model type: carbon atoms connected in a continuous sheet or network (no separate units).

Extended covalent network (crystal-like structure). Continuous networks lack discrete molecular units.
Identify whether this model description is a molecule or crystal: "a pattern repeats without end."

Crystal (extended structure). Endless repetition indicates extended crystal structures.
Which option indicates a crystal model: a fixed number of atoms per unit or an indefinite repeating grid?

An indefinite repeating grid. Crystals extend indefinitely with no fixed number of atoms per structure.
Which type of substance is made of ions in a repeating lattice: ionic compound or molecular compound?

Ionic compound. Ions arrange in continuous lattices, not discrete molecules.
What does the term "lattice" mean in a crystal model?

A regular, repeating 3D arrangement of particles. Particles form an ordered, geometric pattern in crystals.
Which model feature most strongly indicates a substance is molecular: repeating lattice or separate clusters?

Separate clusters (distinct groups) indicate a molecular substance. Molecules exist as isolated units, not connected to each other.

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