Ionic properties: strong lattices and mobile ions
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| mobile ion/ˈməʊbaɪl ˈaɪɒn/ | 可移动离子 | kě yí dòng lí zi |
| electrical conductivity/ɪˈlektrɪkl kɒndəkˈtɪvɪti/ | 导电性 | dǎo diàn xìng |
What would explain this observation?
- A solid salt crystal does not conduct, yet its melt can. The ions have not first appeared on melting; their ability to move has changed.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Ionic compounds have regular giant lattices with strong electrostatic attraction between opposite charges in all directions. Large amounts of energy are needed to overcome many attractions, giving high melting and boiling points. In a solid the ions remain in fixed positions, apart from vibration, and cannot carry charge through the material. When molten, the ions are free to move and conduct. When an ionic compound dissolves in water, mobile ions 可移动离子 in the solution can also carry charge.
- mobile ion: An ion able to move through a liquid or solution and carry charge; electrical conductivity 导电性: The ability of a material to carry electrical charge through itself.
Why does molten sodium chloride conduct?
The carrier is an ion, not a free electron travelling through the salt. Dissolution separates ions into the solution; it does not simply melt the salt. Not every ionic compound is readily soluble, so explain aqueous conductivity only when a dissolved sample is specified. High melting point supports a strong giant structure, while state-dependent conductivity strengthens the ionic interpretation.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- The carrier is an ion, not a free electron travelling through the salt. Dissolution separates ions into the solution; it does not simply melt the salt. Not every ionic compound is readily soluble, so explain aqueous conductivity only when a dissolved sample is specified. High melting point supports a strong giant structure, while state-dependent conductivity strengthens the ionic interpretation.
- Compare teacher-provided data for solid, molten and dissolved samples. High-temperature molten-salt demonstrations require approved equipment and supervision; students can analyse supplied observations instead. For low-voltage solution tests, keep concentration, electrode spacing and immersion depth comparable and use clean apparatus. A brightness comparison is qualitative unless current is actually measured.
Which two habits make the investigation or model in this case more defensible?
Compare teacher-provided data for solid, molten and dissolved samples. High-temperature molten-salt demonstrations require approved equipment and supervision; students can analyse supplied observations instead. For low-voltage solution tests, keep concentration, electrode spacing and immersion depth comparable and use clean apparatus. A brightness comparison is qualitative unless current is actually measured.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: a supplied solution test gives currents 0.18 A and 0.06 A under the same applied voltage and geometry. The current ratio is 0.18/0.06=3. The first sample carries charge at three times the measured rate in this setup, but the result alone does not determine lattice strength or prove the solutions have equal concentration.
Two supplied currents are 0.24 A and 0.08 A. Calculate their ratio, larger/smaller. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Two supplied currents are 0.24 A and 0.08 A. Calculate their ratio, larger/smaller.
The result is 3 . Known: a supplied solution test gives currents 0.18 A and 0.06 A under the same applied voltage and geometry. The current ratio is 0.18/0.06=3. The first sample carries charge at three times the measured rate in this setup, but the result alone does not determine lattice strength or prove the solutions have equal concentration.
Check the conclusion and its limits
- Solid ionic compounds still contain charged ions. Melting does not produce delocalised metallic electrons. Conductivity data must state the sample’s form; testing an insoluble powder in water does not establish the properties of a genuinely dissolved solution.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Solid salt does not conduct because it contains no charged particles. This claim is false: Solid ionic compounds still contain charged ions. Melting does not produce delocalised metallic electrons. Conductivity data must state the sample’s form; testing an insoluble powder in water does not establish the properties of a genuinely dissolved solution.
Ionic properties: strong lattices and mobile ions: The carrier is an ion, not a free electron travelling through the salt. Dissolution separates ions into the solution; it does not simply melt the salt. Not every ionic compound is readily soluble, so explain aqueous conductivity only when a dissolved sample is specified. High melting point supports a strong giant structure, while state-dependent conductivity strengthens the ionic interpretation.
Solid salt does not conduct because it contains no charged particles.
Solid ionic compounds still contain charged ions. Melting does not produce delocalised metallic electrons. Conductivity data must state the sample’s form; testing an insoluble powder in water does not establish the properties of a genuinely dissolved solution.
An ion able to move through a liquid or solution and carry charge: write the technical term.
mobile ion means An ion able to move through a liquid or solution and carry charge.