Short free-response question
Hot copper, water and ice
- Unit 6
- 4 points
- About 9 minutes
You can use a calculator on this question, just like on exam day.
A shorter multipart question that sticks to one or two topics. Each part usually asks for one calculation, claim or explanation. On the exam: 4 questions (Questions 4–7), part of the 1-hour-45-minute free-response section; calculator allowed.
The question
A 50.0 g block of copper is heated to 95.0 °C and then placed in 100.0 g of water at 22.0 °C in an insulated cup. The specific heat capacity of copper is 0.385 J/(g·°C), and the specific heat capacity of water is 4.18 J/(g·°C). Assume no heat is exchanged with the surroundings.
Suggested time: 9 minutes
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Part (a)
1 pointExplain at the particle level how energy is transferred from the copper to the water, and why the transfer eventually stops.
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Part (b)
1 pointCalculate the final temperature of the copper and water.
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Part (c)
1 pointIn a second trial, a 50.0 g block of copper at 95.0 °C is instead placed on a large amount of ice at 0.0 °C. The enthalpy of fusion of ice is 6.01 kJ/mol. Calculate the maximum mass of ice that the copper can melt as it cools to 0.0 °C.
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Part (d)
1 pointWhile the ice is melting, the temperature of the ice-water mixture stays at 0.0 °C even though the copper is transferring energy to it. Explain this observation.
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