Seawater

<p>Seawater, or sea water, is <a href="/facts/Water/0lkXnJPK">water</a> from a <a href="/facts/Sea/7eo8zrRW">sea</a> or <a href="/facts/Ocean/8W8lYgjD">ocean</a>. On average, seawater in the world's oceans has a <a href="/facts/Salinity/X6mB1YAM">salinity</a> of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has approximately 35 grams (1.2 oz) of <a href="/facts/Sea_salt/Gko2CC9k">dissolved salts</a> (predominantly <a href="/facts/Sodium/eYuSPu2V">sodium</a> (Na+) and <a href="/facts/Chloride/m9NUaUDR">chloride</a> (Cl−) <a href="/facts/Ions/wrbwhF3z">ions</a>). The average density at the surface is 1.025 kg/L. Seawater is <a href="/facts/Density/92p6hh9I">denser</a> than both <a href="/facts/Fresh_water/xMP2TxwI">fresh water</a> 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. At typical salinity, it <a href="/facts/Freezing/0kNr25SF">freezes</a> at about −2 °C (28 °F). The coldest seawater still in the liquid state ever recorded was found in 2010, in a stream under an <a href="/facts/Antarctic/xPPVrxBE">Antarctic</a> <a href="/facts/Glacier/8GrKVUSS">glacier</a>: the measured temperature was −2.6 °C (27.3 °F). 
</p><p>Seawater <a href="/facts/PH/RnSv8D7y">pH</a> is typically limited to a range between 7.5 and 8.4. However, there is no universally accepted reference pH-scale for seawater and the difference between measurements based on different reference scales may be up to 0.14 units.
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Seawater open-in-new

Seawater