Water
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White ice, hail, and blue ice

Article 4 Module 1




ice cubes with central white cloud

Ice cubes with trapped white air bubbles

How about ice cubes?

 


It depends on how you freeze the cubes. Household ice cube trays often freeze water relatively quickly.

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This entraps the air bubbles in the center of the cube - the last place to freeze. 



The ice cubes shown above look as if they have clouds trapped in their center. 



Hailstones on grass

Hailstones on grass


Why is hail white?


The feature image shows hail that has fallen on a blue car surface.


Hail is frozen ice compacted together.


However, there are interfaces between the frozen water crystals (which are colorless) and the suspended air pockets (which don't absorb light).


Those disorganized interfaces refract light all over the place. 


The light cannot go through the hailstone and is reflected back to us as white light.

Blue snow and blue water

Blue ice


Why is ice sometimes blue?


In cold regions, glaciers (bodies of dense ice) form over years.


When snow falls on a glacier, it is compressed and becomes frozen water on the surface; the mass of the ice increases over time.


Air bubbles are squeezed out and ice crystals enlarge.


This mass of ice absorbs red lightwaves making the ice appear blue (cyan blue is the result of blue and green lightwaves coming back). 


This is used as a measure of safety by Arctic explorers: The bluer the ice, the safer it is; it is older, thicker. and denser, with no crevices harboring air. Fresh ice, in contrast, is white; it is thin and has air bubbles mixed in between the frozen crystals.


Clear ice cubes

Clear ice cubes: no air bubbles


Clear ice cubes



it is possible to produce perfectly clear ice cubes at home. 



As long as there is slow freezing from the bottom of the cube to the top,  the air is forced up and out.

 


The result is a transparent ice cube through which you can read print!





Conclusion


A disorganized mass of air bubbles held in place by frozen water will reflect light. 



This is the whiteness you see in fast-frozen ice cubes.

Picture Credits:


  1. pfly. Snowy blue car. It kinda hail-snowed. Flickr photo-sharing. Taken on April 18, 2008.
  2. Hijab, J. Ice cubes with entrapped air bubbles. Winter, 2018.
  3. Lee Haywood. Hail on grass. There was a horrendous hailstorm here, which covered the entire ground within a couple of minutes and melted away almost as quickly. Flickr photo-sharing. Taken on March 26, 2010.
  4. Ravas51. Blue icebergs: Img_3457. Flickr - photosharing. Taken on Feb 4, 2013.
  5. Hijab, J. Clear ice cubes with print showing through. Winter 2018.
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