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Name: Rodney H.
Status: educator
Age: 60s
Location: N/A
Country: N/A
Date: 7/23/2004

How much in percent will a given volume of water expand for every 20 degrees Fahrenheit it rises in temperature?

Check out the web site: and on the right hand column click "specific gravity water" scroll down and you will find the data you need.

Vince Calder

Rodney -

Sorry, you cannot get a one number answer, because the density versus temperature is not a straight line. It is a curve, almost a parabola. Liquid water has its maximum density at 3.98 degrees C, and expands for BOTH hotter and colder! At exactly 3.98 degrees C, the thermal expansion coefficient of water is actually zero.

Easy places to see this curve are:

One property of a parabola is: its slope is proportional to your distance from the level point in the middle. So your "percent expansion per 20degF" is less than 0.1% near freezing, rising to almost 0.8% near boiling. The total expansion, from freezing to boiling, is 4.3%. You will have to figure out your most useful way to think about this variable expansion coefficient.

I found that curve-fitting it with a power of roughly 1.75 works better than a power of 2 (a pure parabola).

Jim Swenson

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