The volume of a given weight of water changes with temperature. Water is at its most dense (smallest volume per unit mass) at 4 degrees Celsius or 39.2 degrees Fahrenheit. At this temperature, 1 cubic centimeter or milliliter of water weighs approximately 1 gram.
Weights of Different Volumes at 4 Degrees Celsius
One liter of water weighs 1 kilogram, or 2.2 pounds. A gallon of water weighs 3.78 kg or 8.33 pounds. A cubic foot of water weighs 28.3 kg, or 62.4 pounds. A cubic meter of water weighs 1000 kg, or 2204.6 pounds.
The density of any substance changes based on temperature. In most cases, the hotter a substance, the less dense. This is not the case with water, due to complex interactions between the positively and negatively charged ends of different water molecules and to the crystalline structure of ice. Ice is less dense than liquid water. Only a few other compounds behave this way. For a more detailed list of water densities at different temperatures, see the link in the references.
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Density of Ice and Steam
Ice at 0 degrees Celsius or 32 degrees Fahrenheit has a density of 0.915 grams per milliliter. The density of steam is dependent on the temperature of the steam and the size of its container, or the pressure it is under. Steam at its coolest, which is 100 degrees Celsius or 212 degrees Fahrenheit, has a density of 0.0006 grams per milliliter at normal atmospheric pressure.