this post was submitted on 07 Jun 2023
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[โ€“] SkepticElliptic@beehaw.org 18 points 1 year ago (2 children)

That cold water will boil faster than warm water.

It's a confusion. You should always cook with cold tap water, not hot, because hot tap water can contain excessive amounts of lead.

There are several instances where hot water can freeze faster than lukewarm water. I believe people saw this on shows such as Bill Nye and then forgot the specifics.

[โ€“] OsrsNeedsF2P@lemmy.ml 8 points 1 year ago (4 children)

Wait what's this about hot water and lead? I love me some hot showers, is it making me dumb?

[โ€“] Inductor@feddit.de 9 points 1 year ago

According to the Minnesota Department of Health, if your house was built before 1940, then you should let the water run for 3-5 minutes before drinking it or cooking with it. Showering is probably fine, since they recommend doing showering and running the dishwasher first as one way to let the water run before cooking.
This should especially apply if the water has been sitting in the pipes for a long time (e.g. after a holiday).

If you have a standing hot water tank it will build up with minerals and other stuff over time, it can also harbor bacteria. It's safe for washing with, but you shouldn't make a habit of consuming it.

[โ€“] CmdrShepard@lemmy.one 2 points 1 year ago

I dunno if it contains lead so much as it contains extra minerals from sitting in your waterheater.

[โ€“] Dasnap@lemmy.ml 2 points 1 year ago

It's to add extra flavor.

[โ€“] gnuhaut@lemmy.ml 3 points 1 year ago (2 children)

I will believe that warm water freezes faster only if I see it with my own eyes. It just goes against everything I know about thermodynamics.

[โ€“] conrad82@lemmy.ml 6 points 1 year ago (1 children)

I heard hot water freeze faster when thrown in freezing cold air, because it evaporates faster - making smaller droplets and increasing the surface area

[โ€“] gnuhaut@lemmy.ml 2 points 1 year ago (1 children)

Right, I can believe that. I was thinking of making ice cubes, which is also something I heard.

[โ€“] cnschn@lemmy.cnschn.com 3 points 1 year ago (1 children)

This is actually a thing, it's called the Mpemba effect. It's hella weird (that's the scientific term), but can be reproduced in experiments.

[โ€“] conrad82@lemmy.ml 1 points 1 year ago

We did an experiment in university where we cooled distilled water, which was completely still. We managed to get the temperature down to -7C I think before it froze. It quickly rose to 0C when it started freezing. kinda cool.

I've seen youtubers repeat the experiment, think it's called supercooling. It also causes longer time to freezing, and was one of many theories for the Mpemba effect

[โ€“] SkepticElliptic@beehaw.org 2 points 1 year ago (1 children)

It requires very specific circumstances. Given the same ambient temperature hot water will cool at a faster rate than cooler water because of the greater temperature differential.

Hot water will lose more mass as more will evaporate as it cools.

https://en.m.wikipedia.org/wiki/Mpemba_effect

It's one of those "wacky" physics facts.

[โ€“] gnuhaut@lemmy.ml 4 points 1 year ago

In 2016, Burridge and Linden defined the criterion as the time to reach 0 ยฐC (32 ยฐF; 273 K), carried out experiments, and reviewed published work to date. They noted that the large difference originally claimed had not been replicated, and that studies showing a small effect could be influenced by variations in the positioning of thermometers: "We conclude, somewhat sadly, that there is no evidence to support meaningful observations of the Mpemba effect."

I'm with those guys.