Changes

Water, compared to other compounds, has a number of unusual properties, such as expanding rather than contracting when it freezes. As noted by Lawrence Henderson in his 1913 book, ''The Fitness of the Environment,'' its ability to support life is directly related to some of these unusual properties.  Water has the strongest hydrogen bonding of any known molecule.  This is the reason why it is a liquid at room temperature despite its low molar mass.  Hydrogen bonding also explains why water is less dense as a solid than a liquid.  Water also has an unusually high [[heat capacity]].  [[Heat capacity]] is the ability of a substance to resist changes in temperature.

Water, compared to other compounds, has a number of unusual properties, such as expanding rather than contracting when it freezes. As noted by Lawrence Henderson in his 1913 book, ''The Fitness of the Environment,'' its ability to support life is directly related to some of these unusual properties.  Water has the strongest hydrogen bonding of any known molecule.  This is the reason why it is a liquid at room temperature despite its low molar mass.  Hydrogen bonding also explains why water is less dense as a solid than a liquid.  Water also has an unusually high [[heat capacity]].  [[Heat capacity]] is the ability of a substance to resist changes in temperature.

In 2017, a study (using a computer-generated model) determined that the earth probably produces its own water.  In theory, the heat and pressure beneath the earth's mantle (25 to 250 miles deep) causes [[silicon]] to react with liquid hydrogen and form liquid water and silicon hydride.<ref>https://www.newscientist.com/article/2119475-planet-earth-makes-its-own-water-from-scratch-deep-in-the-mantle</ref>

In 2017, a study (using a computer-generated model) determined that the earth probably produces its own water.  In theory, the heat and pressure beneath the earth's mantle (25 to 250 miles deep) causes [[silicon]] to react with liquid hydrogen and form liquid water and silicon hydride.<ref>[https://www.newscientist.com/article/2119475-planet-earth-makes-its-own-water-from-scratch-deep-in-the-mantle Planet Earth makes its own water from scratch deep in the mantle] www.newscientist.com, 27 January 2017</ref><ref>[https://www.ucd.ie/newsandopinion/news/2017/feb/02/earthswatermayhavebeenformedinitsmantle/ Earth's water may have originally been formed deep within its mantle, study shows] www.ucd.ie, 2 February 2017</ref>

==Saltwater==

==Saltwater==