Chemist/Physicist Question

“This has been bugging me for a while. In my freezer I have to stack my two ice cube trays. The ice cubes on the bottom tray alwyas fracture when I try to pop them out. This suggests the crystal lattice formed has multiple weak points, no? I've taken the empty tray that once contained "perfect cubes" filled it and placed it on the bottom. Then I take the tray with ice fragments still in it and fill the rest of the area up with water. Then place it on top.

The results are the same. The fractured ice has formed with the water for perfect cubes and the tray on the bottom produces fragments.

What's going on?

An idea just occurred to me. Water, unlike every(?) other compound, expands when frozen. The heat release from the bottom tray may not be uniform thus causing uneven/weak crystal formation and/or the top tray is physically interfering with the ice expansion?

But then again, uneven heat release would occur in the top tray that has both solid and liquid water, no?

And if there was physical interference then I would have noted the trays were stuck together, even if it were minimal?

Any ideas?”

“You're thinking way too much and should initiate some more porno threads.”

“Use warm water”

“Time for a beer.”

“This will not go away because I've spent too much time as it is.

WK - If that works than it would seem to only add to the mystery, no?”

“Try freezing beer.”

“Maybe he's porno'ed out.”

“Bear - This is what I think you're saying.

Assuming there were a perfect ice-cube tray, it would not pre-dispose some of the ice to fail, and others to thrive. (hence, your fractured ice example)

The problem with that is the alternative is an "indestructible" ice cube. Is that desireable? I'd argue it is not. You seem to be presuming to know what would make the drink perfect - and that would be one where the ice has "perfect" crystal lattice.

Ice cube manufactures never set out to create a perfect ice cube where nothing fragments. I don't know why you would assume that would be the best "ice tray".
last edited: 12/20/04 4:54:37 PM”

“If this is even a serious question...let the tray set on the counter for a little while before attempting to "pop" them out. The ice will melt slightly and they will slip right out.”

“What the heck would Asaclean Purging Compound have to do with this?”

“WK - If that works than it would seem to only add to the mystery, no?”
Bearmagnet
4:52:22 PM
12/20/04
ignore this user

My wife told me this along time ago. We have an ice maker now, so I cannot tell you the last time we put warm trays of water into the freezer to be frozen and later used to cool off drinks that need to be cooled.

It worked all the time.

I say, "Never argue with a woman. If she says to do something, I do it. If she gives me an answer, I do not question it. If she says, are we lost, I stop at a gas station."”

“How about dropping all of the cubes (broken or not) into a blender with some rum and frozen strawberries? (or with some tequila and margarita mix?)

Bingo! Your problem is solved-- the cubes will all look similar then!”

“Don't talk about ice around this woman.

”

“WK's suggestion to use warm water is a good idea. Warm water freezes faster than cold water. Presumably the tray below the top tray is taking longer to freeze.”

“What about impurities in the water?”

“Like pee?”

“Warm water doesn't freeze faster than cold water, that's a myth. The rate of heat loss is greater for warm water than cold, but it won't freeze first.”

“Sure, I was thinking about city filtration processes, but Pee works.”

“LOL! This is serious! Yes, I post a lot of crap but my "nature" is scientific.

The two trays are identical, placement in the freezer is not. Adding liquid to solid and getting good cubes compounds my interest.

I can see where melting them a little would work b/c the crystal lattice can "reform". But it doesn't solve the question of "why".

Not even going to try the "start with warm water" because that would compound the question.

DH - might initial "rate" have something to do with it?

And this is water from a Britta.
last edited: 12/20/04 5:11:36 PM”

“Put an empty ice tray under them and see what happens.”

“Ha Ha!”

“BM - I noticed this pre-icemaker too.

Is the tray directly on the bottom of the freezer or is there food and stuff between the tray and freezer bottom?

I suspect since the bottom tray contains brittle ice that heat, or lack thereof, is being conducted through the bottom of the freezer and so it freezes quicker. The bottom try is freezing from contact with the air from above and from contact with plastic or metail from below. The top tray is getting cold from air only.”

“Maybe the placing of one tray on top of the other causes uneven air flow under the top tray thus "warm" spots during the freezing process, making some H-bonds stronger then others? Just a guess.”

““Warm water doesn't freeze faster than cold water, that's a myth. The rate of heat loss is greater for warm water than cold, but it won't freeze first.”
dayhiker
5:04:26 PM
12/20/04
ignore this user

Actually hot water can freeze faster than cold water. It is called the Mpemba Effect. Here is a link that explains this phenomenon.

http://math.ucr.edu/home/baez/physics/General/hot_water.html”

“BBW - I've seen that link before but I think it was connected with snopes and busted as myth.

DH - Interesting idea. The bottom tray is touching the freezer surface. You are suggesting two different cooling temperatures of the water in the bottom tray, yes? However, the water in the top tray is beeing cooled by the air and the ice fragments, no? Unless the amount of ice in the top tray has little significant effect?”

“lol bbw posted the link while I was looking for it.”

“Interesting. It doesn't sound like putting water that's 30* warmer in your freezer will qualify though. I didn't read all of that, so they may have addressed it.”

“BM - my freezer in college had a metal bottom. Seems like I felt like that it through more heat into the ice trays than the top tray got from the air alone. It was just my guess. Since I was structural, I didn't have to take thermo, thank the Lord, but that's my guess.”

“that should be threw, not through.”

“I think DH has hit it and I may be able to sleep well. Thanks!

And the Mpemba effect appears to be true!

Water has the most amazing properties, no?”

“Either buy your ice somewhere, get a better refrigerator/freezer, put only one ice tray at a time in there or quit drinking cold drinks. In fact, the cold drinks are probably preventing you from discovering the source of your problem.”

“I think it's like DH said, and that the key factor here is insulation. Trapped air makes for an excellent insulator (this is the magic behind your down sleeping bag).

Most freezers operate by blowing cold air into the freezer compartment. Ususaly, the ice cube tray area has its own blower, or a significant portion of the airflow. The top tray gets more airflow, as there is nothing on top of it to block that flow. The bottom tray doesn't get as much of a draft as the stacked top tray somewhat insulates it.

What if this heat insulation from the liquid water caused enough of a difference to damage the lattice structure of the ice in the bottom tray?”

“Outside at night works here.No beer though.”

“Thats what I said Phantom, ya big.....”

“I think you should clean your ice trays more often.

Friction of crud in the ice basins is widely known to cause ice cube failure.”