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Answers to Readers' Questions on Physical Science:

Mpemba Effect

The following 35 comments and questions have been sent in. They are listed according to date.

List of first 10 items

• Want to do Mpemba Effect
• Want to de Mpemba experiment
• I tried the mpemba effect and need help
• Using ice cube trays with hot and cold water
• Effect works with Zamboni ice resurfacer
• Thinks Mpemba effect is obvious
• What happened to Mpemba afterwards?
• Does temperature difference affect experiment?
• Does supercooling affect Mpemba?
• Can the Mpemba effect work with other substances?

Next 10

Want to do Mpemba Effect

Question

September 30, 2009

mine and jakies science fair project
date:9/30/09
research for projectt do not delete me!!!!!!!!=-]

reyna - USA

18412

Answer

This is a difficult experiment. You had better try it out to see if you can make it work.

Even if you cannot prove that hot water freezes faster than cold water, if you do the experiment well, you should get credit for it.

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Want to de Mpemba experiment

Question

March 10, 2009

what materials do you need?

long - USA

17427

Answer

See: http://www.school-for-champions.com/science/experiments/expmatterstates2.htm
for the experiment.

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I tried the mpemba effect and need help

Question

December 1, 2008

I tried the mpemba effect and I need help

Nicholas - USA

16872

Answer

It is not easy experiment to do.

Take a look at the Reader Feedback to get some ideas about what others have done.

Also see the material on the experiment at:
http://www.school-for-champions.com/science/experiments/expmatterstates2.htm

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Using ice cube trays with hot and cold water

Question

August 22, 2008

A practical application for me would to use the common plastic ice cube trays with cold and hot tap water. Controlling other factors, from which would I get ice cubes first? And approximately how much sooner?

Ted - USA

16388

Answer

It is impossible to estimate time unless all the conditions were known.

This looks like a simple enough experiment to try yourself. You can also try to vary some conditions to seee if you get different results.

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Effect works with Zamboni ice resurfacer

Question

February 18, 2008

My comment about the more rapid freezing of the HOT vs. COLD water dispensed by the Zamboni ice resurfacer at a pro hockey game led to my daughter's info search about this phenomenom which I had recalled from my early 70's high school physics class. Although the explanation given at that time was much more simplistic, we all became believers after a few good lab tests.
I don't recall any reference to the young Mpemba and had just presumed that the Effect was a long-known law of physics.
Thanks for the info.

Jim - USA

15391

Answer

I'm glad the material was useful to you and your daughter.

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Thinks Mpemba effect is obvious

Question

December 5, 2007

Hot water doesn't freeze at all. Only cold water freezes. During the process of cooling the hot water will become the temperature of the colder water and the process would become equal for both of them. A truer statement would be" previously heated water will freeze faster because it doesen't contain as many dissolved gases" The waters are not identical anymore than if one sample was salt water.If you heated two volumns of water and put them in full, sealed containers, kept one heated, then put them in the freezer,they would both contain the same amount of dissolved gasses and the colder sample would freeze first.

The Mpemba effect only proves that water with less dissolved gases freezes faster than water with more dissolved gasses or, fresh water freezes faster than salt water. We all knew that!

J - USA

14909

Answer

Obviously, hot water does not freeze. It must first get cold enough to freeze. But water starting hot freezes faster than water that starts off cold in some situations.

Dissolved gas in the water is only one possible reason for the Mpemba effect. There are numerous parameters that can cause this effect. If "we all knew that" then why have scientists studied this phenomenon so much?

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What happened to Mpemba afterwards?

Question

June 17, 2007

My question is to do with Mpemba himself rather than the Mpemba effect. This happened almost forty years ago in Tanzania. Where was it in Tanzania? and what became of the high school student Mpemba?

Eric - Tanzania

13942

Answer

The student's name was Erasto B. Mpemba and he went to Mkwawa Secondary School in Iringa, Tanzania. Unfortunately, we can't find any information about what happened to him afterwards.

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Does temperature difference affect experiment?

Question

May 6, 2007

I wonder if the Mpemba effect will occur when the all conditions are the same, but the temperature of water, for one of the containers is 20C and 30C for the other???
(I mean the temperature difference is almost small)

Thanks for your attention

Donia - Iran

13717

Answer

It is so difficult to tell how much difference it would make. The experiment seems unpredictable and many scientists still argue on why it happens. Some people see to readily perform the experiment, while others have problems.

Best wishes in making the effect work.

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Does supercooling affect Mpemba?

Question

November 4, 2006

1.DOES THE SUEPRCOOLING AFFECT THE MPEMBA EFFECT ? OT IT HAVE CONNECT WITH THE MPEMBA EFFECT ??
2.IF IT REALLY HAVE MPEMBA EFFECT , OR THE Newton's Cooling Law IS WRONG ???
COULD YOU EXPLAIN IT TO ME ??
THANK YOU !!

YI-PEI - TAIWAN (R.O.C)

12311

Answer

The Mpemba Effect is a special situation and requires correct conditions. I don't believe there is any connection with supercooling. Newton's Cooling Law will hold if all the factors in the Mpemba Effect are considered.

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Can the Mpemba effect work with other substances?

Question

June 1, 2006

do you think the mpemba effect can work on other substances than water if so what kind of substances do you prefer.

michael - USA

11256

Answer

The Mpemba effect seems to require some special circumstances that use characteristics of water. It is possible that the effect can work with other substances, but I've never seen any experiments to prove that.

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