Why are ice cubes grey in the middle?

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Discussion Overview

The discussion revolves around the phenomenon of ice cubes appearing grey in the center, exploring the reasons behind this optical effect. Participants consider aspects of freezing processes, crystal formation, and light behavior in ice.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that the center of the ice cube is less transparent, suggesting that tighter atomic bonding may contribute to this effect, but raises questions about the relationship between bonding and transparency.
  • Another participant explains that the outer layer of the ice freezes faster than the center, leading to larger crystals and potential gas bubbles forming in the middle, which may affect light scattering and transparency.
  • It is mentioned that light gets internally reflected in materials with varying refractive indices, causing scattering and diffusion of light in the central part of the ice cube, resulting in a grey appearance.
  • A comparison is made between the grey appearance of ice and that of a grey cloud, indicating that less light penetrates through the center.

Areas of Agreement / Disagreement

Participants generally agree on the factors contributing to the grey appearance of ice cubes, such as freezing rates and light scattering, but the discussion remains exploratory without a definitive consensus on the underlying mechanisms.

Contextual Notes

Some assumptions about the relationship between atomic bonding and transparency are not fully explored, and the discussion does not resolve the complexities of light behavior in ice.

Who May Find This Useful

This discussion may be of interest to those curious about the physical properties of ice, light behavior in materials, and the effects of freezing processes on transparency.

bobsmith76
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Do you see how the ice-cube is less transparent in the center in this image?

http://p.lefux.com/61/20091013/A10470000C/Crystal-LED-Ice-Cube-1-Gallay.jpg

This image doesn't capture exactly what I see in my cup but it gets my point across. Why is an ice cube less transparent in the center? I'm guess it's because the atoms are more tight bonded in the center. But if that's true then

1. why does that make them less transparent?
2. why are they more tightly bonded in the first place?

I put this question in general physics because it doesn't seem to deal with anyone area of physics except maybe classical physics.
 
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Good question.
The outside freezes much faster than the inside and, the longer the freezing process, the larger the crystals that form. Also, any gas that comes out of the water near the outside will end up as bubbles near the centre, along with ice crystals.
So we have large crystals and possible bubbles in the middle.
Light gets internally reflected when it goes through a (nominally) transparent material if there are changes in refractive index. Light will be scattered and take a longer path on its way through this central part. It will be attenuated and images, seen through it will be diffused, giving a grey appearance..
 
sophiecentaur said:
Good question.
The outside freezes much faster than the inside and, the longer the freezing process, the larger the crystals that form. Also, any gas that comes out of the water near the outside will end up as bubbles near the centre, along with ice crystals.
So we have large crystals and possible bubbles in the middle.
Light gets internally reflected when it goes through a (nominally) transparent material if there are changes in refractive index. Light will be scattered and take a longer path on its way through this central part. It will be attenuated and images, seen through it will be diffused, giving a grey appearance..

Thanks for the explanation, I feel more knowledgeable in this forum..:smile::smile::smile: thanks,,,
 
It's just like a 'grey' cloud. Less light gets through.
 
good question but even better answer. thanks for the help.
 

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