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? Even on a very cloudy days if you dive down in a lake, the water becomes cooler. The warm water is on top because it is lighter.