|MadSci Network: Physics|
It is the same reason that you can crack glass if you heat it too rapidly (such as putting very cold glass in hot water) or cool it too rapidly. Ice is, as you know, a solid, and, although ice at its melting point (or freezing point!) is at about 32 degrees Fahrenheit, solid ice can get colder than that. I suspect the ice is colder than 32 degrees in your freezer. When the ice is put into warm (or warmer than 32 degrees!) soda the mechanical stresses introduced into the ice by the large temperature difference between the part in contact with the soda and the part in the middle make the solid ice crack.
Here's an interesting experiment you and your class can try: Measure the temperature of the ice as it comes out of the freezer, and the temperature of the soda before the ice is introduced. It would be nice if your freezer's temperature can be varied so that you can vary the ice temperature! Is there a minimum temperature difference between the ice and the soda that will cause cracking?
John Link, MadSci Physicist
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