The Mpemba Effect was first discovered by a Tanzanian student while making ice cream in 1969. The Mpemba Effect is the phenomenon whereby hot water can, under certain conditions, freeze faster than cold water.
Scientists have identified a number of factors to explain the Mpemba effect (conduction, evaporation and convection) but so far all the theories are only speculative.
However, back in 2013 Xi Zhang and his colleagues from the Nanyang Technological University in Singapore, found evidence which suggests that it's the chemical bonds that hold water together which provide the strange effect.
Paper:
http://arxiv.org/abs/1310.6514
Articles:
http://www.wired.com/2014/05/whats-up-with-that-mpemba-effect/
http://gizmodo.com/weve-finally-figured-out-why-hot-water-freezes-faster-1455906029
http://phys.org/news/2010-03-mpemba-effect-hot-faster-cold.html
Gif: Throwing boiling water at -41°C
#mpembaeffect #physics
Water is unusual in that it expands (becomes less dense) when frozen so could very well be that heat presets the required expansion of the crystalline hexagonal structure required to freeze water into a solid.
ReplyDeleteNo prob. :)
ReplyDeleteThis was the reason given me by my grade school janitor when he used hot water to flood our school ice rink in winter. That was the 1960s I think. I keep forgetting to try this trick when it's cold. I hide inside. Bubbles freeze nifty too at deep cold temps.
ReplyDelete...thanks
ReplyDeleteVery interesting!
ReplyDeleteMore space between molecules
ReplyDeleteBoiling water has comparatively week intermolecular bonding, as compared to cold water thus give rise to resultant effect
ReplyDeleteEvo Lumin excellent explanation! +1
ReplyDeleteAny good plumber in cold country will tell you the hot water pipes freeze first.
ReplyDeletenick nack
ReplyDeleteOk, I looked at my watch. -check.
I've confirmed the temp -check.
Now what equation does this information apply to? If you could use an example situation and show us the operations that you go through whilst competing said equation that would be fab. Cheers!
All in the hydrogen bonds...
ReplyDeleteThe effect should be to explain the thermodynamic. It is the contribution of entropy... G = H - TS
ReplyDeleteIn the gif it vaporizes and mixes with cold air, cooling more quickly than a blob of liquid water held together by surface tension and insulated from the cold.
ReplyDeleteintresting
ReplyDeleteThe best one I produced was Feb 2015, at minus 40° C using water as close to the boiling point as possible. The temperature gradient was at its' steepest. Love to see them done from great heights !
ReplyDelete