how..? give me true reason...
thank you..
2007-05-13 19:27:39 · 11 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
It's call the Mpemba Effect:
http://en.wikipedia.org/wiki/Mpemba
2007-05-13 19:47:50 · answer #1 · answered by arbiter007 6 · 1⤊ 0⤋
Lets think about this for a moment. Hot water = 90 degrees. Cold water = 60 degrees. If cooling, suppose the temperature of the hot water cooled faster than the cold water because it attracts the cooler temperature more quickly (in fact, the term "cold" is just an absence of heat). By the time the hot water reaches 60 degress (the point at which you started the cold water at), the cold water would have cooled down to lets say 50 degrees at this point. And because the hot water is now at 60 degrees, it will not be cooling as fast as it once did at 90, therefore the colder water at which you started off with, will reach freezing before the hot water. (This is because when cooling the hot water down to the freezing point, it will first become cool water which will slow down that process thereby the cold water you had started with would have already cooled down to a lesser degree.)
2007-05-13 19:44:49 · answer #2 · answered by Ertai2 4 · 1⤊ 0⤋
This is newton's law of cooling. T(t)=Ts+Do^-kt
So this theory of hot water freezing faster than cold water is not true and totally busted. Its a good question to consider though, because the rate at which hot water cools will be much quicker but will slow exponentially as newtons law holds true. This is true reason and will be held up in all cases.
2007-05-13 19:58:20 · answer #3 · answered by boomerite 1 · 1⤊ 0⤋
Yes, Tahoo!
Scientific studies have shown that hot water will actually freeze faster in ice cube trays than cold water. If memory serves me correctly, hot water (150 F average hot water tank temerature) will freeze 8% faster than cold water ( at 55 F). The reasoning is that hot water molecules are more "excited" or active than cold water, therefore the molecules will move around more quickly and change to a solidified state.
The converse is also true. If you start with hot water, it will take less time to reach the boiling point than cold water.
2007-05-13 19:45:54 · answer #4 · answered by tashiasdad 2 · 1⤊ 0⤋
Of coz not! If a hot water is put in an environment with low temperature (for example, freezer), it will need time to lose heat to the surrounding and then it'll freeze. It definitely takes a longer time than the cold water.
For instance, a cup of hot water of 80C and a cold water of 14C, which one do you think its temp will become 0C in the shorter period of time? Of coz is the cold water with only 14C!
2007-05-13 19:37:45 · answer #5 · answered by Anonymous · 1⤊ 0⤋
Hot water takes longer to freeze than cold water. At www.science.com there was an article about scientific myths and this was one of them.
This is one of those times, when logic yeilds the correct answer.
2007-05-13 19:39:41 · answer #6 · answered by Athena 2 · 1⤊ 0⤋
It is true. But not all the time. It depends on the method of cooling used and a few other factors. The reason is unknown.
2007-05-13 19:33:21 · answer #7 · answered by Michael H 2 · 1⤊ 0⤋
I asked that same question several weeks ago, and everyone thought I was stupid, but I have heard that it is true!! I'm not the only one
2007-05-13 19:31:38 · answer #8 · answered by Anonymous · 0⤊ 0⤋
i have heard loads of times and i have heard that scientists cant agree on exactly how it happens, i cant remember ant of the given explanations though, sorry!
2007-05-13 19:31:19 · answer #9 · answered by daniel m 4 · 1⤊ 0⤋
No, its not true, just read that someplace, but don't remember where.
2007-05-13 19:30:38 · answer #10 · answered by Anonymous · 1⤊ 0⤋