/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 34 Compressing air to fill a scuba ... [FREE SOLUTION] | 91Ó°ÊÓ

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Compressing air to fill a scuba tank warms it up. A dive shop compensates by putting the tank in a tub of water, keeping the tank and the gas inside it at a constant temperature as it is filled. If the system is the tank, what are the signs of \(W\) and \(Q\) for this process? What can you say about the relative magnitudes of \(W\) and \(Q ?\)

Short Answer

Expert verified
\'W\' is negative and \'Q\' is zero for this process. The magnitude of \'W\' is greater than the magnitude of \'Q\', because there is no net heat exchange (\'Q\' = 0), while work is done to compress the air in the tank (\'W\' < 0).

Step by step solution

01

Determination of signs for 'W' and 'Q'

In this process, work is done on the system (the tank) in order to compress the air inside it. Therefore, \(W\) is negative. The tank is kept at a constant temperature during the filling process by immersing it in a tub of water. This suggests that there is heat exchange between the tank and the water. However, since the tank’s temperature remains constant, the heat added to the system (the tank) must be equal to the heat lost from the system. Therefore, \(Q\) is zero.
02

Comparison of magnitudes of 'W' and 'Q'

Since \(W\) is negative and \(Q\) is zero, it can be inferred that \(|W| > |Q|\). In fact, as far as their magnitudes are concerned, \(|W|\) (the work done to compress the air) is much greater than \(|Q|\) (which is zero because there is no net heat exchange).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Heat Transfer
In thermodynamics, heat transfer is the process of energy moving from one body to another due to a temperature difference. The scuba tank exercise provides a perfect example. Here, air is compressed into a tank, causing the temperature to rise. Normally, this would cause an increase in temperature. To counteract this, the tank is submerged in water during filling. This water acts as a heat sink, absorbing the excess heat to maintain constant temperature.

This process maintains equilibrium, where the heat lost to the water is exactly equal to the heat gained from compressing the air. Thus, no net heat transfer occurs, resulting in zero net heat added to or removed from the system (\(Q = 0\)). This principle underscores many real-world applications where maintaining a certain temperature is critical, such as in chemical processes or cooling electronic devices, ensuring no damage due to overheating.
Work in Thermodynamics
Work in thermodynamics typically involves energy being transferred by a system to or from its surroundings. When you fill a scuba tank, you compress the air inside. This means you're doing work on the gas, reducing its volume. In thermodynamic terms, when work is done on a system to compress it, the work, \(W\), is negative.

  • Work done on the system (compression): negative \(W\)
  • Work done by the system (expansion): positive \(W\)
This notion highlights the systemic transfer of energy inside the scuba tank scenario. The energy goes into compressing the air, rather than the air doing work by expanding.
Ideal Gas Processes
Ideal gas processes operate under the assumption that gases behave according to the ideal gas law, where pressure, volume, and temperature are interrelated. In our scuba tank example, we're looking at an isothermal process, meaning the temperature remains constant during the compression of the gas.

An isothermal process has distinct characteristics:

  • Temperature stays constant
  • Heat transfer balances out the work done
  • Internal energy does not change
In practical terms, maintaining a constant temperature, as in the scuba tank by submerging it in water, ensures the ideal gas law holds. This law emphasizes the importance of conditions like constant temperature in describing the behaviors and interactions of gases, crucial for industrial and scientific contexts.

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Most popular questions from this chapter

A NATO base in northern Norway is warmed with a heat pump that uses \(7.0^{\circ} \mathrm{C}\) ocean water as the cold reservoir. Heat extracted from the ocean water warms fluid to \(80^{\circ} \mathrm{C} ;\) this warmed fluid is used to heat the building. When the system is working at full capacity, \(2000 \mathrm{kW}\) of heat are delivered to the building at the cost of \(600 \mathrm{kW}\) of electric energy. a. What is the actual coefficient of performance of the system? b. What is the theoretical maximum coefficient of performance of the system?

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