Ice Cube Physics

Dannyalcatraz · Sep 25, 2018

I noticed something about...

Ummm...no.

I mean the frozen water stuff you put in your drinks to chill them. I just took a road trip to Houston and back, and I noticed something: the shape of the ice cubes has a noticeable effect on how they melt.

I was using an insulated travel mug, every time. I’d always fill the mug with as much ice as would fit when I compressed it, but before adding water.

But every time I refilled the ice, the eventual results of melting ended one of two ways: some ice formed into a big cylindrical berg in the middle of the travel mug, other sizes and shapes remained loose the whole time.

Anyone have any insights as to the hows and whys?

Nagol · Sep 25, 2018

How cold was the ice when you put it in? If it was directly from a freezer (as opposed to a hotel ice machine), you might be looking at spot-freezing as the ice is substantially below the freezing point.

Once the water gets cold (somewhere around 40 degree Fahrenheit) warmer (but still cold) water flows to the bottom of the cup while colder water (i.e. the stuff already near the freezing point) collects at the top around the ice. Since the ice is below the freezing point, the already cold water freezes and the ice warms closer to the freezing point. Since heat is entering the cup from the edges, ices around the edge slowly melt providing even more water already at the point of freezing.

Eventually, the ice in the centre gets close to the freezing point itself and spot freezing pretty much stops.

Or maybe you had Maxwell's demon trapped for a while.

Janx · Sep 25, 2018

More science is needed. Come back to houston and we'll do lunch

what was the shape of the ice cubes and their outcome (cylinder or free floaters)?

What was the source of the ice cubes (freezer, or ice machine)?

What was the temperature of the water?

How densely packed was the ice (perhaps by measuring how much water put in)?

Umbran · Sep 25, 2018

Nagol has a lot of it, yes. If the ice is really cold and densely packed, you are very likely to have the surface of the ice melt, and then refreeze into a solid block that then melts from the outside in.

If the ice is warmer, pourous, and not as solidly packed before you add water, you are more likely to have melting around the individual pieces, and then no refreeze.

Dannyalcatraz · Sep 25, 2018

All ice came from dispenser machines of various kinds.

Water was slightly chilled- either bottled & refrigerated or dispensers.

The ice that clumped was largish half moons. The other shapes were those little rough balls/cylinders or the boxy ones with the single hollowed out side.

Since I was “crushing” the ice a bit, it was as tightly packed as I could get it. But I can see based on the commentary above that the boxy, semihollowed ice would have a lot more surface area for the water to act upon.

Jhaelen · Sep 26, 2018

Looking at the subject I thought this would be about the IceCube Neutrino Observatory...

Janx · Sep 26, 2018

Jhaelen said:
Looking at the subject I thought this would be about the IceCube Neutrino Observatory...

But still, it's a cool topic...

Dannyalcatraz · Oct 20, 2018

Well...partially solved. It’s a packing problem.

I have been watching the way the half-moon cubes from my freezer settle, both from the dispenser, and then later as the water gets added; intact and after using the dispenser’s grinder.

As the cubes settle, the vast majority of those curved cubes tend to do so with the curve facing the curved walls of the mug. This means they’re already in somewhat of a cylindrical shape before they freeze together and fuse into a slug.