Ice Crackling

[T'ai Chi]

I notice that the ice I put in a glass usually crackles when I poor in the water. I'd assume this is due to the water being hotter than the ice?

My main question is, is there a minimum temperature of the water where you'd expect the ice to crackle?

Thanks in advance for any info!

[Iamme]

T'ai---Well...you KNOW there IS going to be some point at which this occurs, and some point that it don't.

You could change the scenario from cold to hot. You could ask, "At what temperature will a cast iron metal engine crack, if the engine is (say)600 degrees and you put 'cooler' water on it? If you dump 500 degree water on it, will it crack? 400? 300? 200? 211? 73.5? 50.7? You KNOW there is going to be SOME point...but knowing the exact degree? Hmmmm. SOMEbody maybe knows. But not ME.

An ice cube becomes larger than the volume of water from which it was made. Thus, it floats because it is less dense than the same volume of water that you drop it in. When you add hot water, you are heating up the outside of the ice faster than the inside of the ice, and when you do this with ANYthing...something has to give. Being that ice is brittle, it stands to reason that it will crackle.

Now I have a tantalizing question: You know that lake ice will crack. These cracks appear to be open, like a fault line. If ice expands, and cracks, you would expect a heaving at the crack site, from compression. And you would expect to see exploding shrapnel from this effect (like when roads buckle and eplode/crack in the heat of summer). Are the cracks caused by SHRINKAGE of the ice (as opposed to expansion of the water volume during the freezing process) because ice, even though it expands from the water stage, now actually shrinks, when the temperature of the ice gets colder?