Discovery Information
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Who: Henry Cavendish |
When: 1766 |
Where: England |
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Name Origin
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Greek: hudor (water) and gennan (generate) |
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Sources
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Found chiefly combined with oxygen in the form of water, also found in mines and oil and gas wells. Stars contain a virtually unlimited supply hydrogen and
in the universe, hydrogen is the most abundant element (hydrogen makes up 75% of the mass of the visible universe and over
90% by number of atoms.).
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Uses
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Hydrogen's uses include: being used in the production of ammonia (NH3), ethanol (C2H5OH), hydrogen chloride (HCl) and hydrogen bromide (HBr); the hydrogenation of vegetable oils; hydrocracking, hydroforming
and hydrofining of petroleum; atomic-hydrogen welding; instrument-carrying balloons; fuel in rockets; and cryogenic research.
Its two heavier isotopes, deuterium (D) and tritium (T), are used respectively for nuclear fission and fusion.
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Hydrogen fuel cells are being investigated as mobile power sources with lower emissions than hydrogen-burning internal combustion
engines. The low emissions of hydrogen in internal combustion engines and fuel cells are currently offset by the pollution
created by hydrogen production. This may change if the substantial amounts of electricity required for water electrolysis
can be generated primarily from low pollution sources such as solar energy or wind. Research is being conducted on H2 as a replacement for fossil fuels.
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Notes
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Hydrogen is a tasteless, colorless, odorless and extremely flammable gas, it is also the lightest chemical element. |
At standard temperature and pressure, hydrogen exists as the diatomic gas, H2, with a boiling point of 20.27 K, and a melting point of 14.02 K. Under extreme pressures, such as those at the center of
gas giants, the molecules lose their identity and the hydrogen becomes a metal (metallic hydrogen). Under the extremely low pressure in space - virtually
a vacuum - the element tends to exist as individual atoms, simply because it is statistically unlikely for them to combine.
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A unique property of hydrogen is that its flame is nearly invisible in air. |