Water (common) is a substance described by the chemical formula H2O, the most abundant compound on earth, consisting of two hydrogen atoms and one oxygen atom, a solvent for mineral salts.
Density of water as a function of temperature
It is generally accepted that the density of water is 1000 kg/m3 , 1000 g/l or 1 g/ml, but do we often think at what temperature these data were obtained?
The maximum density of water is reached at a temperature of 3.8…4.2°C. Under these conditions, the exact density of water is 999.972 kg/m3 . This temperature dependence of density is typical only for water. Other common liquids do not have a density maximum on this curve—their density decreases uniformly as temperature rises.
Water exists as a separate liquid in the temperature range from 0 to a maximum of 374.12°C – this is its critical temperature at which the interface between liquid and water vapor disappears. The density of water at these temperatures can be found in the table below. Data on the density of water are presented in units of kg/m3 and g/ml.
The table below shows the density of water in g/ml for different temperatures between 0 and 100 °C.
| temperature, °С | density, g/ml | temperature, °Сdensity, g/ml | |
| 0 | 0.99987 | 52 | 0.9872 |
| 2 | 0.99997 | 54 | 0.9862 |
| 4 | 1.00000 | 56 | 0.9853 |
| 6 | 0.99997 | 58 | 0.9843 |
| 8 | 0.99988 | 60 | 0.9832 |
| 10 | 0.99973 | 62 | 0.9822 |
| 12 | 0.99953 | 64 | 0.9811 |
| 14 | 0.99927 | 66 | 0.9801 |
| 16 | 0.99897 | 68 | 0.9789 |
| 18 | 0.99862 | 70 | 0.9778 |
| 20 | 0.99823 | 72 | 0.9767 |
| 22 | 0.99780 | 74 | 0.9755 |
| 24 | 0.99733 | 76 | 0.9743 |
| 26 | 0.99681 | 78 | 0.9731 |
| 28 | 0.99626 | 80 | 0.9718 |
| 30 | 0.99568 | 82 | 0.9706 |
| 32 | 0.99506 | 84 | 0.9693 |
| 34 | 0.99440 | 86 | 0.9680 |
| 36 | 0.99372 | 88 | 0.9667 |
| 38 | 0.99300 | 90 | 0.9653 |
| 40 | 0,99225 | 92 | 0.9640 |
| 42 | 0,99147 | 94 | 0.9626 |
| 44 | 0.9907 | 96 | 0.9612 |
| 46 | 0.9898 | 98 | 0.9598 |
| 48 | 0.9890 | 100 | 0.9584 |
| 50 | 0.9881 |
It should be noted that as the water temperature increases (above 4°C), its density decreases. For example, according to the table, the density of water at a temperature of 20°C is 998.2 kg/m3 , and when it is heated to 90°C, the density value decreases to a value of 965.3 kg/m3. The specific gravity of water under normal conditions differs significantly from its density at high temperatures. The average density of water at a temperature of 200-370°C is much less than its density in the usual temperature range from 0 to 100°C.
A change in the state of aggregation of water leads to a significant change in its density. Thus, the density of ice at 0°C is 916-920 kg/m3 , and the density of water vapor is a hundredth of a kilogram per cubic meter. It should be noted that the value of the density of water is almost 1000 times greater than the density of air under normal conditions.
