Ice expands when it freezes, if it can't expand it won't freeze. When you hit the bottle the dent gives part of the ice a gap to expand in and it ripples down the bottle. I've only seen this done by simply removing the top.

Yeah I've done this accidentally by puting bottles of water in the freezer. Tip it back to drink and it starts to freeze as soon as it hits the neck of the bottle.

Supercool !

5 stars for Satch.

I loves me some Ice Nine brand drinking water.

Uh, liquids are almost always denser than solids. The molecules are packed tighter together...

Shit, wait, I thought most elements and molecules are denser in solid form than liquid, let alone gas.

:(

I am ignorant.

You are only ignorant in that you listen to glasseye.
What he's spewing is the Modest Mouse of science.

You were right. Solids are by far the least energetic of the four common phases. Less energy means less movement by individual molecules, and the "tighter packed" and more cohesive an object becomes. Liquids tend to be a little less dense, and gases even less so, then plasmas are the least dense.

Water is different for reasons I can't remember. Maybe its molecular geometry? I know its phase chart is basically backwards compared to most other compounds.

Treat yourself and read the first few chapters of Richard Feynman's "6 Easy Pieces". Water is a polar molecule, like a little Lego piece, and ice is a 6-sided crystal with a lot of empty space.

It's really obvious once you see a good drawing of how ice forms. Think of a snowflake.. they always have 6 sides and lots of empty space. That pattern goes all the way down to the molecular level.

j lzrd is right, water is a goddamned oddity, and it's possible that life cannot evolve without lots and lots of it.

Kill it with fire.