Chapter 5: Problem 204
When helium is allowed to expand into vacuum heating effect is observed. This is because (1) helium is a noble gas (2) the inversion temperature of helium is very low (3) helium is an ideal gas (4) the boiling point of helium is the lowest among the elements
Short Answer
Expert verified
The inversion temperature of helium is very low. (Option 2)
Step by step solution
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Helium Properties
Helium is unique due to its distinct properties. It is a noble gas, meaning it rarely reacts with other elements. The atomic number of helium is 2, and it is the second lightest and second most abundant element in the universe. One remarkable property of helium is its exceptionally low boiling point of -268.9°C. This makes helium suitable for applications in cryogenics and superconducting magnets. Helium is also known for its low density and high thermal conductivity.
These properties mean that helium does not easily form compounds and remains in a gaseous state at extremely low temperatures. It is an ideal gas in many scenarios, but it's crucial to understand that its behavior changes at very low temperatures.
These properties mean that helium does not easily form compounds and remains in a gaseous state at extremely low temperatures. It is an ideal gas in many scenarios, but it's crucial to understand that its behavior changes at very low temperatures.
Exploring Gas Expansion
Gas expansion occurs when a gas moves from a region of higher pressure to a region of lower pressure. This can be observed, for instance, when a gas expands into a vacuum. During expansion, the gas molecules spread out to fill the available space. For most gases, expansion into a vacuum results in cooling, as predicted by the Joule-Thomson effect. However, helium behaves differently due to its unique properties.
The temperature and pressure during expansion play a critical role in determining whether the gas cools or heats up. For gases like helium, the inversion temperature—where the gas ceases to cool and starts to heat up—can be exceptionally low. When helium expands and reaches a temperature higher than its inversion temperature, it heats up instead of cooling.
The temperature and pressure during expansion play a critical role in determining whether the gas cools or heats up. For gases like helium, the inversion temperature—where the gas ceases to cool and starts to heat up—can be exceptionally low. When helium expands and reaches a temperature higher than its inversion temperature, it heats up instead of cooling.
Inversion Temperature and Thermodynamics
Thermodynamics studies energy, work, and heat within systems, particularly focusing on laws governing these exchanges. The inversion temperature is a term in thermodynamics describing the temperature at which a gas switches from cooling upon expansion to heating up. For helium, this temperature is very low, meaning it frequently encounters temperatures higher than its inversion temperature during expansion.
This behavior is closely related to the Joule-Thomson effect, which describes how the temperature of a real gas changes as it expands or contracts without performing work (i.e., in a vacuum). Most gases cool upon expansion; however, above their inversion temperature, gases like helium heat up. This is pivotal in understanding helium's behavior in various applications, especially those involving low temperatures and vacuum conditions.
This behavior is closely related to the Joule-Thomson effect, which describes how the temperature of a real gas changes as it expands or contracts without performing work (i.e., in a vacuum). Most gases cool upon expansion; however, above their inversion temperature, gases like helium heat up. This is pivotal in understanding helium's behavior in various applications, especially those involving low temperatures and vacuum conditions.
