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Explanation of how to do the Mpemba Effect experiment for states of matter - Succeed in Physical Science. Also refer to physics, solids, liquids, gases, temperature, freezing, boiling, changing states, Ron Kurtus, School for Champions. Copyright © Restrictions

Experiments with States of Matter: 
Mpemba Effect -
Freezing Hot Water Faster than Cold Water

by Ron Kurtus (revised 17 August 2002)

The Mpemba Effect states that hot water changes its state from liquid to solid--or freezes--faster than cold water. This does not seem to make sense, but it has been discovered to be true.

Goal of experiment

The goal is to compare the time is takes to freeze a container of water at various starting temperatures of the water, under the same conditions.

Conditions

In any good experiment, you want to change only one variable and keep everything else to the same. You must also be able to determine when you achieved the outcome of the experiment.

Factors

Factors that must remain the same are:

The only thing you vary is the initial temperature of the water.

When frozen

Possible ways to determine when the water is frozen include:

Experiment

You can do the experiment using one or even several containers that you place in a freezer compartment.

One container in freezer

If you use one container, fill it with hot water, put it in a freezer and measure the time it takes the water to freeze. Then repeat the experiment with exactly the same amount of water in the same container at a cooler temperature. Do this a number of times, reducing the initial temperature of the water.

Two or more containers in freezer

Or, you could take two or more containers of the same size, shape and material and put exactly the same amount of water--but different temperatures-- into each. Then you put them both in the freezer and see which freezes first. The reason the containers must be exactly the same is because the shape and material of the container affects the rate of heat loss.

Outside in winter

In either of the above cases, you would have to periodically open the freezer to see if the water is freezing. An alternative would be to place the containers outside during the winter when the temperature was below freezing. You could then easily watch the freezing process from a window in your house.

Data

By comparing the time it takes to freeze for the various starting water temperatures, you should be able to find a situation where warmer water freezes faster than water at a colder temperature.

Jump to Where can you go from here?

Resources

The Mpemba Effect - Hot water Freezes before Cold - School for Champions

Can hot water freeze faster than cold water? - University of California Dept of Physics

Hot Water Freezes Faster Than Cold - United Kingdom Usenet Physics FAQ

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Mpemba Effect - Freezing Hot Water Faster than Cold Water

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