When making a tray of ice cubes, I often find a cube or two with a spike of ice rising straight up off it after freezing. It looks almost like a drop of water hitting a larger body of water, but inverted. I can’t wrap my head around the physics of how such a spike could form. If there’s condensation inside my freezer, it wouldn’t form liquid drops, and surely wouldn’t freeze in this matter. Is irregular freezing within the cube forcing water upwards as the rest freezes around it? Any ideas?
Welcome to the SDMB. We can answer any question 24 hours a day.
Here is a recent thread with links to definitive answers on this odd phenomena.
http://boards.straightdope.com/sdmb/showthread.php?t=330978&highlight=spikes
In case you are the lazy clciker type:
http://www.physics.utoronto.ca/~smorris/edl/icespikes/icespikes.html
"The short explanation is this: as the ice freezes fast under supercooled conditions, the surface can get covered except for a small hole. Water expands when it freezes. As freezing continues, the expanding ice under the surface forces the remaining water up through the hole and it freezes around the edge forming a hollow spike. Eventually, the whole thing freezes and the spike is left.
A slightly longer explanation: the form of the ice crystals depends on the cooling rate and hence on the degree of supercooling. Large supercooling favors sheets which rapidly cover the surface, with some sheets hanging down into the water like curtains. These crystalites tend to join at 60 degrees and leave triangular holes in the surface. Hence, spikes often have a triangular base. The sides of the spike are sometimes a continuation of pre-existing subsurface crystalites, and can extend from the surface at steep angles."
Thanks for the welcome (rather than a search first, post second slap-on-the-wrist) and answer!
I am not sure guests can search but paid members can. Somehow the Chicago Reader talked thousands of people with lots of odd bits of knowledge to pay for the privilege of answering other people’s questions 24/7 and with using good manners in the process. It is unique business model for sure and pretty unique in the world.
Well I’ll be; I -can’t- search. And just when I felt bad for getting a quick answer to an already-been-asked question. Another Chicago Reader feature for not making guests feel bad, and tempting them to sign up?
I got some great links from your reply. I think this was the most impressive: http://www.physics.utoronto.ca/~smorris/edl/icespikes/Lozowski_icespike.avi