Water Density and Temperature

As water warms, it expands.* At 50° F a pound of water has a volume of 15.37 ounces. However, a 150° F pound of water has a volume of 15.86 ounces. Let's look at a water density versus temperature plot.

The plot shows that water density decreases as temperature increases. Warm water weighs less than cool water. Does this match your experience? If you dive down into a lake, even on a very cloudy day, the water becomes cooler. The warm water is on top because it is lighter.

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* This is not true for water between 32° F and 39.2° F.