WTF, I can't boil water...

lybogany

¬¬'
Registered Senior Member
Just Kidding. But why would cold water boil faster than hot water? I haven't performed a controlled experiment on this but from a logical standpoint:

If I have water at 20 degrees centigrade and water at 70 degrees centigrade both in identical pots over the same output of heat, wouldn't the hotter water reach 100 degrees centigrade first? This is all done at sea level, none of that high altitude "I can boil water at 50 degrees" crap.

Explain?
 
Hotter water takes less time to boil than colder water.
I've observed that while making tea (you can call that an experiment :p)
It's probably due to the fact that the water molecules are already in faster motion, i.e., no energy and time is needed to get them to a 70C state because they already are there.
Higher temperatures means that the molecules move at higher speeds. The slower the motion, the colder the material.
 
Ok. But then why would hot water freeze faster that cold water? (In certain conditions)
 
I don't know, I've never tried to get my tea to a freezing temperature. :D
Let's wait for someone else to answer.
 
i think you are gettnig it the worng way around(i assume english is your second language). cold water will freeze faster than hot water
 
No really, its the Mpemba effect , that hot water can actually freeze faster than cold, again in certain situations.

and BTW, I was born in the USA, so english is my first language TY :p
 
With hot water freezing quicker than cold, I just think of it in basic terms of those faster molecules getting tired out quicker before those that continuously go slow will be able to last longer thereby taking longer to freeze. Kinda like seeing who will drown first. The person frantically splashing about or the one remaining calm under the water.

I've another question though. Why is it that if you take a plastic gallon jug of lukewarm water that's 3/4 or less full and then shake it a bunch of times, why does it start getting colder? This is what I usually do to give the numerous jugs of water I have lying about to get a quick sip of cold water rather than warm. Wouldn't those faster molecules wind up getting hotter, not colder?

- N
 
nieldo,

more of the water is being exposed to the temperature of the barrel, so it will adjust to that temperature faster
 
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