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At 20 °C (68 °F) one liter of water can dissolve about 357 grams of salt, a concentration of 26.3 percent by weight (% w/w). At 100 °C (212 °F) (the boiling temperature of pure water), the amount of salt that can be dissolved in one liter of water increases to about 391 grams, a concentration of 28.1% w/w.
Cross section showing the water table varying with surface topography as well as a perched water table Cross-section of a hillslope depicting the vadose zone, capillary fringe, water table, and the phreatic or saturated zone. (Source: United States Geological Survey.) The water table is the upper surface of the zone of saturation.
Salinity is an ecological factor of considerable importance, influencing the types of organisms that live in a body of water. As well, salinity influences the kinds of plants that will grow either in a water body, or on land fed by a water (or by a groundwater). [19] A plant adapted to saline conditions is called a halophyte.
Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply [1] [2] and 90% of habitable space on Earth. [3] Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems. [4]
The average density at the surface is 1.025 kg/L. Seawater is denser than both fresh water and pure water (density 1.0 kg/L at 4 °C (39 °F)) because the dissolved salts increase the mass by a larger proportion than the volume. The freezing point of seawater decreases as salt concentration increases.
Brine (or briny water) is water with a high-concentration solution of salt (typically sodium chloride or calcium chloride).In diverse contexts, brine may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of that of solutions used for brining foods) up to about 26% (a typical saturated solution, depending on temperature).
In the technical terms of physical chemistry, the minimum freezing point of a water-salt mixture is −21.12 °C (−6.02 °F) for 23.31 wt% of salt. Freezing near this concentration is however so slow that the eutectic point of −22.4 °C (−8.3 °F) can be reached with about 25 wt% of salt.
Thus a relative density less than one relative to water means that the substance floats in water. The density of a material varies with temperature and pressure. This variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object and thus increases its density.