Question
Fri August 31, 2012 By:

why do water contracts when temperature is increased from 0 to d Degree Celsius?

Expert Reply
Fri August 31, 2012

As materials are heated, the molecules gain kinetic energy and therefore tend to expand and get less dense. If they are cooled, they tend to contract and get denser. But an important exception is water. The range that is different for water is between 0 and 4 degrees Celsius. Water at any other temperature would expand when it is heated, and contract when cooled.

At 4 degrees Celsius, water is at its most contracted state, but it isn't frozen. It doesn't freeze until 0 degrees Celsius. This means as it goes toward 0 degrees it expands because of the crystallization of the water into ice. This results from a rearrangement of the oxygen and hydrogen bonds present in water into stronger and more complex attachments. Because water at 0 degrees Celsius is more expanded than at 4 degrees Celsius, water heated from zero degrees will shrink from its crystallized state until it makes it back to 4 degrees. Beyond 4 degrees, the water will start to expand again.

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