If the conditions are just right, then water will be forced out of the hole in the ice and it will freeze into an ice spike, a bit like lava pouring out of a hole in the ground to makes a volcano. But water does not flow down the sides of a thin spike, so in that way it is different from a volcano. Rather, the water freezes around the rim of the tube, and thus adds to its length.
The spike can continue growing taller until all the water freezes, cutting off the supply, or until the tube freezes shut. The tallest spike we've seen growing in an ordinary ice cube tray was 56mm 2.
Why Distilled Water? Most ice cube trays produce a few spikes, but usually only if distilled water is used. Millions of people make ice cubes every day using ordinary tap water, and most don't see ice spikes.
Oddly enough, some people often get plenty of ice spikes using ordinary tap water, but this appears to be rare. I have some ideas about why distilled water might make ice spikes more readily than tap water, but so far I cannot explain why some tap waters make copious ice spikes.
We measured the probability of ice spike formation as a function of salt NaCl concentration in distilled water, at a fixed temperature of -7C, which is shown in the graph at right. Very little salt is needed to kill the ice spikes.
As this ice expands around the outside, it forces the remaining liquid water inwards, until it no longer has anywhere to go but up and out. As this escaping water makes contact with the freezer air, the outside molecules quickly freeze and expand, and the spike keeps getting long and longer until it freezes shut at the end - it's a process that's kind of hard to explain in writing, but you can see a great illustration of it in the video above.
But why are these water escape routes always so spiky and knife-like? Go Paperless with Digital. Stephen Morris, professor of experimental nonlinear physics at the University of Toronto, maintains a Web page on just this topic. So we asked him to tackle the question: Water is one of those rare materials that expands while it freezes.
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Ice spikes form rarely in nature, but you can make them in your own freezer quite simply and reliably. Here's what you do. All you need is water, an ice cube tray, and a freezer:. It's important to use distilled or reverse osmosis purified water. Ordinary tap water or mineral water contain dissolved substances that may prevent the water from forming spikes or reduce the number of spikes that are formed.
You can substitute a bowl or cup for the ice cube tray. Plastic ice cube trays are nice because they contain several small compartments, meaning you have a quick freeze time and several chances for spikes.
Plastic ice cube trays are preferred for this project, but it's unknown whether it's the tray material or the size of the cubes that improve the effect. It's easy! Simply pour the distilled water into the ice cube tray, set the tray in your freezer, and wait. You can expect about half of the ice cubes to contain ice spikes.
The spikes degrade and soften over time since most home freezers are frost-free and will blow warmer air over the spikes. Pure water supercools , which means it remains liquid past the ordinary freezing point.
When it starts to freeze at this lower temperature, it solidifies very rapidly. The freezing process starts at the edges of the container because the nicks, scratches, and imperfections allow for nucleation of the ice crystals. Freezing continues until there is only a hole near the middle of the container, which contains liquid water. Ice is less dense than liquid water , so some of the crystals float to the top and are pushed out, forming a spike.
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