What in the heck is in my water?

So, I found something equally interesting and distressing today. A couple days ago I turned down the temperature in my fridge to test my new fridge thermometer. Unsurprisingly, the temperature in my fridge went down below freezing (30-31 F) according to the thermometer.

Now here is the worrisome part. I have several containers of water in my fridge right now. One is Brita filtered water from my tap, and the other is steam purified water that I bought in a plastic jug from Giant. The Brita filtered water is completely frozen solid, whereas the water from Giant is still fluid.

What the hell is in that water? :confused:

Are the containers the same size/shape? I’m wondering if surface area might be affecting heat transfer.

Your purified water might possibly be supercooled.

No, the containers are different sizes. The Giant brand water is being kept in what amounts to a gallon milk jug, whereas the Brita filtered water is in a cylindrical plastic container. The water has been in there for more than long enough to be adequately chilled though (over 24 hours), so I doubt it’s a simple matter of insulation.

The distilled water is pure enough that the water molecules are having a hard time finding a site to form the first ice crystal. This seems like BS but I’ve seen it before.

Open the jug and drop a bit of ice in. Congratulations, you are now Kurt Vonnegut. :slight_smile:

Are the two jugs on the same shelf? In my fridge it is not uncommon for things on the top shelf next to the cold air inlet get a little frozen, with no signs of icing in beverages in the door or on lower shelves.

The super-cooled liquid idea is plausible too.

There are numeorus possibilities here that have nothing to do with unusual additives. Several have already been suggested. To add two more

Salt lowers the freezing point of water, even relatively small amounts of salt. So it may be that the frozen water contains more impurities.

Pressure also plays a role. Water is most dense just above freezing, and then expands rapidly upon freezing. If you can resist those expansion and contraction events you increase the time/energy transfer needed to freeze the water. IOW if one container is rigid and one deforms, or one deforms only outwards and the other only inwards, you’re gonna get freezing occurring at different times/temperatures.

Ahh I think you hit the bullseye. On second examination, the Giant brand water was inside a sealed plastic jug and it had indeed collapsed slightly. The Brita water was open to the air. I guess pressure was involved somehow.

Nitpick: most dense at roughly 4 C or 40 F. Whether that counts as “just above” is a judgment call on the reader’s part.

Maybe we can stop right there. A full gallon of water is going to take longer to cool down than a quart.

Just thought I’d add my own $.02.

My refrigerator is terribly inconsistent temperature-wise. The average temp is around 40 F… but there’s a particular spot about six inches wide on two shelves where you can count on things to freeze. I think that’s where the cold air enters the fridge near the top and then descends. Put two identical bags of lettuce next to each other back there and one stays perfect and fresh and the other freezes solid. We’ve had more than a few pitchers of liquid freeze.