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Checking How a Melt Pack Resets 4 questions
Checking How a Melt Pack Resets
Base your answers on the information provided and your knowledge of chemistry. Use the 2025 Chemistry Reference Tables as needed.
A display pack contains 20 g of a material that melts at 28 °C. The model requires 50 J to melt each gram at that temperature. After a test the entire pack is liquid. The class cools it before trying to use its melting capacity again.
| Reset method | Mass that has become solid before reuse (g) | Temperature at start of next use (°C) |
|---|---|---|
| P | 20 | 28 |
| Q | 12 | 28 |
Question 1
Which recorded value determines how much of each pack can melt again at 28 °C?
- The initial pack mass alone
- The mass that is already liquid
- The measured solid mass before reuse
- The starting temperature alone
Question 2
Calculate how much energy each pack can absorb by melting on reuse. Show how the reset record enters the calculation.
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The display needs a pack that can absorb 800 J through melting. The class may continue cooling Q at 28 °C so that more of its material becomes solid.
Question 3
Calculate the minimum additional mass that must solidify in Q to reach the requirement.
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A third pack has just cooled to 28 °C. A separate phase measurement shows that none of its material has solidified yet.
Question 4
Use the third pack and Q to evaluate the claim that a reading of 28 °C establishes how much energy a pack can absorb by melting on reuse.
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