Try the official question
Official NYSED sample · Smartphone Chemistry · Question 2
Selected stimulus for this question. The complete cluster is linked below.
Most smartphone display screens are made of aluminosilicate glass. This electrically conductive glass is composed of an oxide of silicon and aluminum with sodium ions dispersed throughout the surface. Some aluminosilicate glass is made stronger by immersing the glass in a bath of molten potassium salt at 400°C. This causes some sodium ions to be replaced by potassium ions. The potassium ions are compressed in the spaces between molecules in the glass. This makes the glass harder and more resistant to breakage, but less conductive.
Since glass is an insulator, the glass screen is coated with a layer of transparent indium tin oxide. This layer is highly conductive and allows the screen to act as a conductive touch screen.
2. Explain why the particulate-level structure of the glass prevents the potassium ions in the glass from functioning as a conductor. [1]
Your response: Write your explanation before reading on.
Read the original NYSED sample, page 1 · See the complete Smartphone Chemistry cluster
Worked reasoning · New Regents explanation
1. Identify what the prompt asks you to explain
The prompt asks about potassium ions in the glass. Naming glass as an insulator repeats the result; it does not explain the role of the particles or their surroundings. Keep the ions separate from the conductive indium tin oxide coating described in the next paragraph.
2. Name the structural cause from the stimulus
The potassium ions are compressed into small spaces in the glass structure. This describes how the material holds those ions in place. Your answer must refer to that structure, rather than only saying that the ions are immobile.
3. Connect the structure to movement and conduction
An ion has electric charge. For ions to conduct through a material, they must be able to move through it and carry charge. Here, the small spaces hold the potassium ions in place, so those ions cannot move through the glass to carry charge.
4. Write the causal link in one connected explanation
New Regents example response
The potassium ions are trapped in small spaces in the glass structure, so they cannot move through the glass to carry electric charge.
The response connects structure → restricted ion movement → inability of those ions to conduct. This is a useful way to organize this answer, not a required sentence template or word count. No calculation or reference-table lookup is needed for this particular explanation.
What the official scoring guide requires
Official NYSED scoring guidance · Question 2
New Regents interpretation: Include the structural reason the ions cannot move. The guide explicitly rejects an answer that only says immobile potassium ions cannot conduct without referring to the glass structure. Equivalent explanations are allowed; you do not have to copy one official example.
Strengthen an incomplete explanation
| Response | What it explains | What to improve |
|---|---|---|
| “The glass does not conduct.” | States the result. | Add what the glass structure does to the potassium ions. |
| “The potassium ions cannot move.” | Identifies restricted movement. | Explain that small spaces in the glass structure hold the ions in place. |
| “The ions are trapped in small spaces in the glass structure and cannot move to carry charge.” | Connects structure, movement, and conduction. | This gives the structural explanation requested; other equivalent wording can also work. |
These are teaching examples, not additional official scoring rules. Use the actual question and its rating guide when reviewing a response.
Common mistakes to catch
- Saying there are no charged particles. Potassium ions are charged. The issue here is their restricted movement in the glass structure.
- Discussing only electrons or the screen coating. The question asks why the potassium ions do not function as charge carriers in this material.
- Stopping at “the ions cannot move.” Include the structural cause: small spaces in the glass hold the ions in place.
- Applying the same carrier explanation to every conductor. Conducting metals have mobile electrons. Molten salts can conduct through mobile ions. Identify the material and charge carrier in the question.
Practice structure and conductivity in another setting
Work the complete Smartphone Chemistry sample to connect the glass explanation with the phone’s other materials and reactions. You have seen Q2’s solution, so treat a repeat as supported practice.
For a different conductivity question, All About Aluminum includes a question about how the structure of aluminum supports its use in power transmission. Work out which charge carrier is mobile before choosing an answer. That full-exam workspace cluster requires membership; its public overview and official exam PDF are available without an account.
Use the smartphone context for a moles calculation · All free Chemistry sample clusters · Review another topic