Does the expansion of air affect the overall volume increase of a glass stopper?

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Discussion Overview

The discussion revolves around the effect of temperature on the volume of a glass stopper with a hollow section, specifically whether the expansion of air within the hollow should be considered alongside the expansion of the glass itself. The scope includes theoretical considerations of thermal expansion and the implications of different assumptions about the contents of the hollow.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that the volume of the hollow in the glass stopper increases with temperature and questions whether the expansion of air should be included in calculations.
  • Another participant argues that the thermal expansion of glass is stress-free and proposes that the hollow can be treated as if it were filled with glass, implying that the expansion would be uniform.
  • A subsequent reply clarifies that the original question involves a hollow in the glass stopper, not a solid piece fitting into it.
  • Further, a participant challenges the assumption of treating the hollow as filled with glass, suggesting that considering air in the hollow could lead to a greater final volume due to the expansion of both materials.

Areas of Agreement / Disagreement

Participants express differing views on whether the expansion of air should be considered alongside the expansion of glass, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

There are assumptions about the nature of the materials involved and the conditions under which expansion occurs that are not fully explored, such as the specific properties of air and glass at varying temperatures.

zorro
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Suppose there is a glass stopper with a hollow in it. If the ambient temperature rises the volume of the hollow(say 1cm3 initially) also rises. To find out the increase in volume, do we have to take into account the expansion of air along with the expansion of glass?
 
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Unconstrained thermal expansion is stress-free. So you can imagine that a glass piece fits into the hollow and expands stress-free; therefore, the hollow expands as if it were filled with glass, not air. Does this help?
 
Mapes said:
So you can imagine that a glass piece fits into the hollow and expands stress-free

The question does not say about the glass fitting in a hollow. There is a hollow in the glass stopper.
 
Read my answer again: imagine that the hollow part is filled with glass. It would expand the same amount.
 
Okay, I get you now.
But is that not loss of generality? If we consider some amount of air to be present in the hollow, both of them will expand which can lead to a different final volume (greater) compared to your case.
 

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