Mindboggling

[unixronin]

Last week's weather was really ugly at times, and in particular, we had one night when it rained, then snowed, then rained, then snowed ...  It ended up with the driveway covered several inches deep in slush too heavy for the snowblower to shift.  Then the slush froze, leaving an ice crust thick enough to drive on.  I wound up, in desperation, hooking up the hosepipe to a hot-water faucet to get the ice off the driveway.  (This wasn't as absurdly energy-intensive as it sounds.  The ice was spongy, and melted very rapidly under a strong jet of hot water.

While I was doing this, one of our neighbors said, "You know hot water freezes faster than cold water, right?  Try it in your freezer sometime, put an ice tray of hot water and one of cold in there, and the hot water will freeze first."

I was so gobsmacked I just didn't know what to say.  I've heard some ridiculous urban legends in the past, but this one ... I just don't know where to start.  Where on earth does anyone get such a totally wrong-headed idea?  It falls down on even the very simplest of examination — the hot water's got to get cold before it can freeze, and that's going to take time, so the only way the hot water can freeze faster is if some cold water freezes faster than other water, but how do you know you didn't get magic fast-freezing water out of the cold tap in the first place?  To freeze before the water that started out cold, with both trays being cooled at the same rate, the hot water would have to cool to the starting temperature of the cold water in negative time.

Snopes is silent on this one.

The only way I can think of that someone could "prove"this to themself is if they inadvertently put the tray of hot water right under the cold-air inlet to the freezer compartment, so that it's being much more strongly cooled than the other.

Comments

[tabbifli.livejournal.com]

Actually, I do know where this belief comes from in the US, and it's got nothing to do with all the tests and supercooled and de-gassed and evaporated and whatever experiments listed above. It's pretty stupid, actually.

Non-self defrosting freezers.

After iceboxes, when inset freezers first started coming about, they were frequently coated in a thick covering of frost (much like your driveway, really). You can't defrost these freezers (or at least you shouldn't) by taking a knife or an icepick to them, and it's a hassle and three halves to unplug the damn thing - it involves unplugging the whole darn fridge.

On the other hand, if you put an ice cube tray full of HOT water in the freezer, you start melting off all the frost, and it sucks the heat right out of the hot water, just to freeze up solid, quick as that. Clean freezer and fresh ice, what do you think?

As it turns out, the freezer actually DID freeze the hot water faster than the cold while it was defrosting - faster ice cubes, defrosted freezer - and the ice box frosted over about every 2 or 3 days, depending on what you put in them. As a result, it got rather firmly embedded in the American mindset, from about the mid-40s onward, that hot water freezes faster than cold.

I really wish I'd known about this particular trick in the first apartment we lived in back in Pittsburgh, too. I burned out a hairdryer defrosting that damn freezer.

[olafthunderfoot.livejournal.com]

i used to defrost mine with a small hammer!