(II) A 64-kg ice skater moving at 8.5 m/s glides to a stop. Assuming the ice is at 0°C and that 50% of the heat generated by friction is absorbed by the ice, how much ice melts?
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22. The First Law of Thermodynamics
First Law of Thermodynamics
Problem 32b
Textbook Question
(I) An ideal gas expands isothermally, performing 4.30 x 103 J of work in the process. Calculate the heat absorbed during this expansion.

1
Step 1: Understand the process described in the problem. The gas expands isothermally, meaning the temperature remains constant throughout the process. For an ideal gas undergoing an isothermal process, the first law of thermodynamics simplifies to ΔU = 0, where ΔU is the change in internal energy.
Step 2: Recall the first law of thermodynamics: ΔU = Q - W, where Q is the heat absorbed by the system and W is the work done by the system. Since ΔU = 0 for an isothermal process, the equation simplifies to Q = W.
Step 3: Identify the given values in the problem. The work done by the gas during the expansion is W = 4.30 × 10³ J. Since Q = W for an isothermal process, the heat absorbed by the gas will be equal to the work done.
Step 4: Substitute the given value of W into the equation Q = W. This will allow you to calculate the heat absorbed during the expansion.
Step 5: Conclude that the heat absorbed by the gas is numerically equal to the work done, as per the relationship Q = W in an isothermal process. Ensure units are consistent and properly expressed in joules (J).

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Ideal Gas Law
The Ideal Gas Law describes the relationship between pressure, volume, temperature, and the number of moles of an ideal gas. It is expressed as PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is temperature. This law is fundamental in understanding gas behavior under various conditions, particularly during processes like expansion or compression.
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Isothermal Process
An isothermal process occurs at a constant temperature, meaning that any heat added to the system is used to do work rather than change the internal energy. For an ideal gas, this implies that the internal energy remains constant, and the heat absorbed by the gas equals the work done by the gas. This concept is crucial for calculating heat transfer in thermodynamic processes.
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Entropy & Ideal Gas Processes
First Law of Thermodynamics
The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. In the context of an isothermal expansion, this law can be expressed as ΔU = Q - W, where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system. Since the internal energy change is zero in an isothermal process, the heat absorbed equals the work done.
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The First Law of Thermodynamics
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