What can a solid’s behavior reveal about its particles?
You will be able to: Connect molecular, ionic, metallic and network solids to mobility and bonding.
What can a solid’s behavior reveal about its particles?
An unknown solid does not conduct electricity until it melts. Another conducts while solid and bends under force. Testing properties can help distinguish particle arrangements.
A useful starting point: How do attractions affect boiling and flow? →
Words and symbols before equations
- Molecular solid
- Distinct molecules held together by intermolecular attractions.
- Ionic solid
- An extended arrangement of cations and anions.
- Metallic solid
- Metal cores held together with mobile delocalized electrons.
- Network solid
- Atoms connected by extended covalent bonding.
What this picture assumes
Finite structural cartoons, not crystallographic unit cells. Molecular lines are within discrete molecules; network lines connect a continuing covalent structure. Boundaries omit further neighbors.
Read the picture in three steps
- Read the species and labels first. Identify what each symbol and line represents. Read the units and fixed conditions before comparing quantities.
- Separate covalently bonded molecules; attractions between them. This is a static, schematic projection; optional 3D changes only the viewing angle.
- Check what the picture assumes below. Use the Explore task to predict one change before moving a control.
Connect the picture to the chemistry
A solid conducts only when charge carriers can move through it. Ions fixed in an ionic lattice cannot carry current across the solid, but mobile ions in a melt often can. Metallic electrons can move even in the solid.
Many ionic solids are brittle: shifting layers can bring like charges near each other. Metals often deform while maintaining attraction between cores and mobile electrons.
Molecular solids often melt relatively easily because melting mainly overcomes attractions between molecules. Network solids generally require disrupting extended strong bonding and have high thermal stability. Graphite is an important conducting, layered exception to simple network-solid rules.
| Type | Building units | Charge carriers |
|---|---|---|
| Molecular | Separate molecules | Usually no mobile charge carriers |
| Ionic | Cations and anions | Ions mobile in melt or solution, not ordinary solid |
| Metallic | Cores + delocalized electrons | Mobile electrons even in solid |
| Network | Extended covalent atoms | Usually poor conduction; graphite is a key exception |
A worked example, step by step
Solid X is brittle, does not conduct as a solid, and conducts when molten. Choose the most consistent solid type.
- Nonconduction in the solid suggests no mobile charge carriers there.
- Molten conduction shows charges become mobile on melting.
- A brittle ion lattice fits both observations.
- Ionic is the best-supported classification, although a real identification uses multiple measurements rather than one clue.
“Contains charged particles” is insufficient for conductivity; those charges must be mobile.
Why can solid copper conduct while solid NaCl does not?
Compare with an explanation
Copper has mobile delocalized electrons. In solid NaCl, the ions occupy fixed lattice positions.
Predict. Change one thing. Explain.
Switch between the four solid models. Identify whether the connected object is a molecule, an ion array, a metallic array or a covalent network; explain the charge carriers.
On narrow screens, swipe or scroll diagrams sideways to read all labels.
Separate covalently bonded molecules; attractions between them. This is a static, schematic projection; optional 3D changes only the viewing angle.
Finite structural cartoons, not crystallographic unit cells. Molecular lines are within discrete molecules; network lines connect a continuing covalent structure. Boundaries omit further neighbors.
Explain what you noticed: Answer the investigation prompt above. State one observation and explain it using particle interactions, concentration, gas behavior or energy transfer. Identify what the representation cannot tell you.
Apply the idea to a fresh problem Practice →Show what you understand.
Two original questions are a starting check, not proof of mastery. Explain your choice before revealing the answer.
Original written challenge
4 points · self-check · not an official AP questionCompare a metal and an ionic solid: identify particles, explain solid-state conductivity, and explain their different response to a shifted layer.
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Compare with the answer and four-point rubric
- 1 point: A metal has positive cores and delocalized electrons; an ionic solid has cations and anions.
- 1 point: Mobile electrons permit metallic conduction.
- 1 point: Fixed ionic sites prevent bulk ion motion in the solid.
- 1 point: A metal can maintain cohesion during rearrangement; an ionic shift can align like charges and lead to fracture.
Accept equivalent correct methods and explanations. This is a Refresh Kid teaching rubric, not an official AP scoring guideline.
Retrieve it before you reveal it.
RECALL 1What is the key conductivity question?
Which charged particles can move?
RECALL 2What distinguishes molecular and network solids?
Separate molecules versus an extended covalent structure.
RECALL 3Does one measured property prove identity?
No; combine multiple observations and structural evidence.
Revisit these tomorrow and a week later. Try a fresh problem and explain why the method applies.
What can a solid’s behavior reveal about its particles?
- Conductivity requires mobile charges.
- Use several observed properties to infer a structure.
Remember: “Contains charged particles” is insufficient for conductivity; those charges must be mobile.
Conditions: Finite structural cartoons, not crystallographic unit cells. Molecular lines are within discrete molecules; network lines connect a continuing covalent structure. Boundaries omit further neighbors.
Refresh Kid · AP Chemistry Unit 3 · Objectives 3.2.A · Review edition
Framework, scope and review status
Mapped to College Board CED, Topic 3.2, objective 3.2.A. CED effective Fall 2024 and June 2026 clarifications checked September 16, 2026. Unit 3: Properties of Substances and Mixtures, Topics 3.1–3.13. Focused lesson names, examples, models and assessments are original Refresh Kid teaching materials, not additional official topics or official AP questions. Official corrections.
The model states its assumptions beside the diagram. Colligative-property calculations and solution molality/mass-percent/volume-percent calculations are not required here. The optional speed-density model illustrates distributions; it does not require memorizing its mathematical derivation.
Teaching resources: The Organic Chemistry Tutor video titles/descriptions and topic coverage were checked for optional links; no claim is made to have watched every video. No creator scripts, examples, worksheets or artwork were copied. GitHub’s 3D website collection and its Three.js camera-control example informed the idea of controllable spatial inspection. Scientific diagrams, geometry and interactions here are original. The self-hosted Three.js runtime retains its MIT license. Camera rotation changes the view, not the chemistry.
Independent teacher review and observation of students remain pending. Implementation checks do not certify scientific accuracy, accessibility or learning effectiveness. This is a review edition.
Optional official resource: Released AP Chemistry questions and scoring guides. This archive contains questions across units; it is not an assignment of every question to this lesson.
The teaching sequence is informed by the IES learning guide; this exact implementation has not been evaluated with learners.
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