Phase Change and Lowest Boiling Point

In summary, the conversation discusses the limitations of using gas as a shock absorbing cushion, specifically the concern that under high pressure, the gas may liquefy and lose compressibility. The question asks which of the given gases would be the best to use in light of this concern, with the correct answer being A (CO2) due to its low boiling point. The answer key does not provide an explanation for this, leading to confusion and questioning about the reasoning behind choosing a gas with a low boiling point. The conversation also considers the scenario of using a gas with a boiling point just below or above room temperature and how it would affect its effectiveness as a shock absorber.
  • #1
Dorj
1
0
I am studying for the MCAT and I am having a hard time understanding the rationale for the following question from my review:

Q: One of the limitations of using a gas as a shock absorbing cushion is that under high pressure, the gas may liquefy and lose compressibility. Which of the following gases would be the best one to use in light of this concern? A. CO2, B. Water vapor, C. Bromine gas, D. Ammonia gas.

The correct answer was A as it had the lowest boiling point and the answer key just states that we want to pick the gas with the lowest boiling point, without explaining why. I am having a hard time understanding why, isn't it more reasonable to go with a gas with a higher boiling point in a high pressure situation, so that more of it remains in the gaseous form.

I am confused. Can someone please explain why lower bp is better in this context.
 
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  • #2
What if its boiling point were just below room temperature? Wouldn't pressurizing it cause it to immediately condense? How about if its boiling point were even HIGHER that room temperature? Still a good gas for this application?
 
  • #3
To put it differently - imagine filling a shock absorber wit water at room temperature. Would it work?
 

1. What is a phase change?

A phase change is the transformation of matter from one physical state to another, such as from a solid to a liquid or from a liquid to a gas.

2. What factors affect the phase change of a substance?

The phase change of a substance is primarily affected by temperature and pressure. Other factors such as intermolecular forces and molecular structure also play a role.

3. What is the lowest boiling point?

The lowest boiling point is the temperature at which a substance changes from a liquid to a gas at standard atmospheric pressure. This varies depending on the substance, but the lowest boiling point of any element is -252.9°C for helium.

4. How does a substance's boiling point relate to its lowest boiling point?

A substance's boiling point is the temperature at which it changes from a liquid to a gas at standard atmospheric pressure, while the lowest boiling point is the lowest temperature at which it can change from a liquid to a gas under any pressure. Therefore, the boiling point is always equal to or higher than the lowest boiling point.

5. Why is the lowest boiling point important in scientific research?

The lowest boiling point is important in scientific research because it can give insight into the nature of a substance and its intermolecular forces. It is also crucial in understanding the behavior and properties of substances in extreme environments, such as in space or at very low temperatures.

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