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What is something many people believe but is not true? (lemmy.ml)

submitted 1 year ago by [email protected] to c/[email protected]

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[–] [email protected] 2 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.

[–] [email protected] 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

[–] [email protected] 1 points 1 year ago (1 children)

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

[–] [email protected] 2 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.

[–] [email protected] 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

[–] [email protected] 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.

[–] [email protected] 3 points 1 year ago

In 2016, Burridge and Linden defined the criterion as the time to reach 0 °C (32 °F; 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.