States of Matter Experiment: Use Mpemba Effect to Freeze Hot Water Faster than Cold Water

(updated 21 November 2022)

The Mpemba Effect states that under certain circumstances 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.

This lesson will answer those questions.

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Purpose of experiment

The purpose 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 temperature of the freezer
• The amount of water in the container
• The size, shape and material of the container
• Any type of air motion over the water

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

When frozen

Possible ways to determine when the water is frozen include:

• Use a thermometer or temperature probe in the water to see when the temperature near the bottom levels off at the freezing point.
• Visibly check to determine when the water in the container is frozen; perhaps a clear container would help.

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.

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Try something new

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Resources and references

Websites

The Mpemba Effect – Hot Water Freezes before Cold – Lesson in School for Champions

Experiments Resources